service method - Page 359

Domain-Driven-Design question

- by Michael

Hello everyone, I have a question about DDD. I'm building a application to learn DDD and I have a question about layering. I have an application that works like this: UI layer calls = Application Layer - Domain Layer - Database Here is a small example of how the code looks: //****************UI LAYER************************ //Uses Ioc to get the service from the factory. //This factory would be in the MyApp.Infrastructure.dll IImplementationFactory factory = new ImplementationFactory(); //Interface and implementation for Shopping Cart service would be in MyApp.ApplicationLayer.dll IShoppingCartService service = factory.GetImplementationFactory<IShoppingCartService>(); //This is the UI layer, //Calling into Application Layer //to get the shopping cart for a user. //Interface for IShoppingCart would be in MyApp.ApplicationLayer.dll //and implementation for IShoppingCart would be in MyApp.Model. IShoppingCart shoppingCart = service.GetShoppingCartByUserName(userName); //Show shopping cart information. //For example, items bought, price, taxes..etc ... //Pressed Purchase button, so even for when //button is pressed. //Uses Ioc to get the service from the factory again. IImplementationFactory factory = new ImplementationFactory(); IShoppingCartService service = factory.GetImplementationFactory<IShoppingCartService>(); service.Purchase(shoppingCart); //**********************Application Layer********************** public class ShoppingCartService : IShoppingCartService { public IShoppingCart GetShoppingCartByUserName(string userName) { //Uses Ioc to get the service from the factory. //This factory would be in the MyApp.Infrastructure.dll IImplementationFactory factory = new ImplementationFactory(); //Interface for repository would be in MyApp.Infrastructure.dll //but implementation would by in MyApp.Model.dll IShoppingCartRepository repository = factory.GetImplementationFactory<IShoppingCartRepository>(); IShoppingCart shoppingCart = repository.GetShoppingCartByUserName(username); //Do shopping cart logic like calculating taxes and stuff //I would put these in services but not sure? ... return shoppingCart; } public void Purchase(IShoppingCart shoppingCart) { //Do Purchase logic and calling out to repository ... } } I've seem to put most of my business rules in services rather than the models and I'm not sure if this is correct? Also, i'm not completely sure if I have the laying correct? Do I have the right pieces in the correct place? Also should my models leave my domain model? In general I'm I doing this correct according DDD? Thanks!

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WCF TCP Protocol

- by jobless-spt

I want to host a WCF service with TCP Protocol. I can host the service using IIS or Windows Service. I need to know what port I need to open for this service for it to be accessible by client?

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Jaxws notifications

- by akmer

Hi, Could you please help in the following? Is there an acceptable design guideline to implement WS Notification Messaging in java? My scenario is the following: a web service client makes a web service call to a web service. After that, the web service should be able to send asynchronous notifications to the web client (as a result of the first web method call). What approach should be used? Thank you, Regards

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Is this right in the use case of exec method of child_process? is there away to cody the envirorment along with the require module too?

- by L2L2L

I'm learning node. I am using child_process to move data to another script to be executed. But it seem that it does not copy the hold environment or I could be doing something wrong. To copy the hold environment --require modules too-- or is this when I use spawn, I'm not so clear or understanding spawn exec and execfile --although execfile is like what I'm doing at the bottom, but with exec... right?-- And I would just love to have some clarity on this matter. Please anyone? Thank you. parent.js - "use strict"; var fs, path, _err; fs = require("fs"), path = require("path"), _err = require("./err.js"); var url; url= process.argv[1]; var dirname, locate_r; dirname = path.dirname(url); locate_r = dirname + "/" + "test.json";//path.join(dirname,"/", "test.json"); var flag, str; flag = "r", str = ""; fs.open(locate_r, flag, function opd(error, fd){ if (error){_err(error, function(){ fs.close(fd,function(){ process.stderr.write("\n" + "In Finally Block: File Closed!" + "\n");});})} var readBuff, buffOffset, buffLength, filePos; readBuff = new Buffer(15), buffOffset = 0, buffLength = readBuff.length, filePos = 0; fs.read(fd, readBuff, buffOffset, buffLength, filePos, function rd(error, readBytes){ error&&_err(error, fd); str = readBuff.toString("utf8"); process.env.str = str; process.stdout.write("str: "+ str + "\n" + "readBuff: " + readBuff + "\n"); fs.close(fd, function(){process.stdout.write( "Read and Closed File." + "\n" )}); //write(str); //run test for process.exec** var env, varName, envCopy, exec; env = process.env, varName, envCopy = {}, exec = require("child_process").exec; for(varName in env){ envCopy[varName] = env[varName]; } process.env.fs = fs, process.env.path = path, process.env.dirname = dirname, process.env.flag = flag, process.env.str = str, process.env._err = _err; process.env.fd = fd; exec("node child.js", env, function(error, stdout, stderr){ if(error){throw (new Error(error));} }); }); }); child.js - "use strict"; var fs, path, _err; fs = require("fs"), path = require("path"), _err = require("./err.js"); var fd, fs, flag, path, dirname, str, _err; fd = process.env.fd, //fs = process.env.fs, //path = process.env.path, dirname = process.env.dirname, flag = process.env.flag, str = process.env.str, _err = process.env._err; var url; url= process.argv[1]; var locate_r; dirname = path.dirname(url); locate_r = dirname + "/" + "test.json";//path.join(dirname,"/", "test.json"); //function write(str){ var locate_a; locate_a = dirname + "/" + "test.json"; //path.join(dirname,"/", "test.json"); flag = "a"; fs.open(locate_a, flag, function opd(error, fd){ error&&_err(error, fs, fd); var writeBuff, buffPos, buffLgh, filePs; writeBuff = new Buffer(str), process.stdout.write( "writeBuff: " + writeBuff + "\n" + "str: " + str + "\n"), buffPos = 0, buffLgh = writeBuff.length, filePs = buffLgh;//null; fs.write(fd, writeBuff, buffPos, buffLgh, filePs-3, function(error, written){ error&&_err(error, function(){ fs.close(fd,function(){ process.stderr.write("\n" + "In Finally Block: File Closed!" + "\n"); }); }); fs.close(fd, function(){process.stdout.write( "Written and Closed File." + "\n");}); }); }); //} err.js - "use strict"; var fs; fs = require("fs"); module.exports = function _err(err, scp, cd){ try{ throw (new Error(err)); }catch(e){ process.stderr.write(e + "\n"); }finally{ cd; } }

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Creating a dynamic proxy generator with c# – Part 3 – Creating the constructors

- by SeanMcAlinden

Creating a dynamic proxy generator with c# – Part 1 – Creating the Assembly builder, Module builder and caching mechanism Creating a dynamic proxy generator with c# – Part 2 – Interceptor Design For the latest code go to http://rapidioc.codeplex.com/ When building our proxy type, the first thing we need to do is build the constructors. There needs to be a corresponding constructor for each constructor on the passed in base type. We also want to create a field to store the interceptors and construct this list within each constructor. So assuming the passed in base type is a User<int, IRepository> class, were looking to generate constructor code like the following: Default Constructor public User`2_RapidDynamicBaseProxy() { this.interceptors = new List<IInterceptor<User<int, IRepository>>>(); DefaultInterceptor<User<int, IRepository>> item = new DefaultInterceptor<User<int, IRepository>>(); this.interceptors.Add(item); } Parameterised Constructor public User`2_RapidDynamicBaseProxy(IRepository repository1) : base(repository1) { this.interceptors = new List<IInterceptor<User<int, IRepository>>>(); DefaultInterceptor<User<int, IRepository>> item = new DefaultInterceptor<User<int, IRepository>>(); this.interceptors.Add(item); } As you can see, we first populate a field on the class with a new list of the passed in base type. Construct our DefaultInterceptor class. Add the DefaultInterceptor instance to our interceptor collection. Although this seems like a relatively small task, there is a fair amount of work require to get this going. Instead of going through every line of code – please download the latest from http://rapidioc.codeplex.com/ and debug through. In this post I’m going to concentrate on explaining how it works. TypeBuilder The TypeBuilder class is the main class used to create the type. You instantiate a new TypeBuilder using the assembly module we created in part 1. /// <summary> /// Creates a type builder. /// </summary> /// <typeparam name="TBase">The type of the base class to be proxied.</typeparam> public static TypeBuilder CreateTypeBuilder<TBase>() where TBase : class { TypeBuilder typeBuilder = DynamicModuleCache.Get.DefineType ( CreateTypeName<TBase>(), TypeAttributes.Class | TypeAttributes.Public, typeof(TBase), new Type[] { typeof(IProxy) } ); if (typeof(TBase).IsGenericType) { GenericsHelper.MakeGenericType(typeof(TBase), typeBuilder); } return typeBuilder; } private static string CreateTypeName<TBase>() where TBase : class { return string.Format("{0}_RapidDynamicBaseProxy", typeof(TBase).Name); } As you can see, I’ve create a new public class derived from TBase which also implements my IProxy interface, this is used later for adding interceptors. If the base type is generic, the following GenericsHelper.MakeGenericType method is called. GenericsHelper using System; using System.Reflection.Emit; namespace Rapid.DynamicProxy.Types.Helpers { /// <summary> /// Helper class for generic types and methods. /// </summary> internal static class GenericsHelper { /// <summary> /// Makes the typeBuilder a generic. /// </summary> /// <param name="concrete">The concrete.</param> /// <param name="typeBuilder">The type builder.</param> public static void MakeGenericType(Type baseType, TypeBuilder typeBuilder) { Type[] genericArguments = baseType.GetGenericArguments(); string[] genericArgumentNames = GetArgumentNames(genericArguments); GenericTypeParameterBuilder[] genericTypeParameterBuilder = typeBuilder.DefineGenericParameters(genericArgumentNames); typeBuilder.MakeGenericType(genericTypeParameterBuilder); } /// <summary> /// Gets the argument names from an array of generic argument types. /// </summary> /// <param name="genericArguments">The generic arguments.</param> public static string[] GetArgumentNames(Type[] genericArguments) { string[] genericArgumentNames = new string[genericArguments.Length]; for (int i = 0; i < genericArguments.Length; i++) { genericArgumentNames[i] = genericArguments[i].Name; } return genericArgumentNames; } } } As you can see, I’m getting all of the generic argument types and names, creating a GenericTypeParameterBuilder and then using the typeBuilder to make the new type generic. InterceptorsField The interceptors field will store a List<IInterceptor<TBase>>. Fields are simple made using the FieldBuilder class. The following code demonstrates how to create the interceptor field. FieldBuilder interceptorsField = typeBuilder.DefineField( "interceptors", typeof(System.Collections.Generic.List<>).MakeGenericType(typeof(IInterceptor<TBase>)), FieldAttributes.Private ); The field will now exist with the new Type although it currently has no data – we’ll deal with this in the constructor. Add method for interceptorsField To enable us to add to the interceptorsField list, we are going to utilise the Add method that already exists within the System.Collections.Generic.List class. We still however have to create the methodInfo necessary to call the add method. This can be done similar to the following: Add Interceptor Field MethodInfo addInterceptor = typeof(List<>) .MakeGenericType(new Type[] { typeof(IInterceptor<>).MakeGenericType(typeof(TBase)) }) .GetMethod ( "Add", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, new Type[] { typeof(IInterceptor<>).MakeGenericType(typeof(TBase)) }, null ); So we’ve create a List<IInterceptor<TBase>> type, then using the type created a method info called Add which accepts an IInterceptor<TBase>. Now in our constructor we can use this to call this.interceptors.Add(// interceptor); Building the Constructors This will be the first hard-core part of the proxy building process so I’m going to show the class and then try to explain what everything is doing. For a clear view, download the source from http://rapidioc.codeplex.com/, go to the test project and debug through the constructor building section. Anyway, here it is: DynamicConstructorBuilder using System; using System.Collections.Generic; using System.Reflection; using System.Reflection.Emit; using Rapid.DynamicProxy.Interception; using Rapid.DynamicProxy.Types.Helpers; namespace Rapid.DynamicProxy.Types.Constructors { /// <summary> /// Class for creating the proxy constructors. /// </summary> internal static class DynamicConstructorBuilder { /// <summary> /// Builds the constructors. /// </summary> /// <typeparam name="TBase">The base type.</typeparam> /// <param name="typeBuilder">The type builder.</param> /// <param name="interceptorsField">The interceptors field.</param> public static void BuildConstructors<TBase> ( TypeBuilder typeBuilder, FieldBuilder interceptorsField, MethodInfo addInterceptor ) where TBase : class { ConstructorInfo interceptorsFieldConstructor = CreateInterceptorsFieldConstructor<TBase>(); ConstructorInfo defaultInterceptorConstructor = CreateDefaultInterceptorConstructor<TBase>(); ConstructorInfo[] constructors = typeof(TBase).GetConstructors(); foreach (ConstructorInfo constructorInfo in constructors) { CreateConstructor<TBase> ( typeBuilder, interceptorsField, interceptorsFieldConstructor, defaultInterceptorConstructor, addInterceptor, constructorInfo ); } } #region Private Methods private static void CreateConstructor<TBase> ( TypeBuilder typeBuilder, FieldBuilder interceptorsField, ConstructorInfo interceptorsFieldConstructor, ConstructorInfo defaultInterceptorConstructor, MethodInfo AddDefaultInterceptor, ConstructorInfo constructorInfo ) where TBase : class { Type[] parameterTypes = GetParameterTypes(constructorInfo); ConstructorBuilder constructorBuilder = CreateConstructorBuilder(typeBuilder, parameterTypes); ILGenerator cIL = constructorBuilder.GetILGenerator(); LocalBuilder defaultInterceptorMethodVariable = cIL.DeclareLocal(typeof(DefaultInterceptor<>).MakeGenericType(typeof(TBase))); ConstructInterceptorsField(interceptorsField, interceptorsFieldConstructor, cIL); ConstructDefaultInterceptor(defaultInterceptorConstructor, cIL, defaultInterceptorMethodVariable); AddDefaultInterceptorToInterceptorsList ( interceptorsField, AddDefaultInterceptor, cIL, defaultInterceptorMethodVariable ); CreateConstructor(constructorInfo, parameterTypes, cIL); } private static void CreateConstructor(ConstructorInfo constructorInfo, Type[] parameterTypes, ILGenerator cIL) { cIL.Emit(OpCodes.Ldarg_0); if (parameterTypes.Length > 0) { LoadParameterTypes(parameterTypes, cIL); } cIL.Emit(OpCodes.Call, constructorInfo); cIL.Emit(OpCodes.Ret); } private static void LoadParameterTypes(Type[] parameterTypes, ILGenerator cIL) { for (int i = 1; i <= parameterTypes.Length; i++) { cIL.Emit(OpCodes.Ldarg_S, i); } } private static void AddDefaultInterceptorToInterceptorsList ( FieldBuilder interceptorsField, MethodInfo AddDefaultInterceptor, ILGenerator cIL, LocalBuilder defaultInterceptorMethodVariable ) { cIL.Emit(OpCodes.Ldarg_0); cIL.Emit(OpCodes.Ldfld, interceptorsField); cIL.Emit(OpCodes.Ldloc, defaultInterceptorMethodVariable); cIL.Emit(OpCodes.Callvirt, AddDefaultInterceptor); } private static void ConstructDefaultInterceptor ( ConstructorInfo defaultInterceptorConstructor, ILGenerator cIL, LocalBuilder defaultInterceptorMethodVariable ) { cIL.Emit(OpCodes.Newobj, defaultInterceptorConstructor); cIL.Emit(OpCodes.Stloc, defaultInterceptorMethodVariable); } private static void ConstructInterceptorsField ( FieldBuilder interceptorsField, ConstructorInfo interceptorsFieldConstructor, ILGenerator cIL ) { cIL.Emit(OpCodes.Ldarg_0); cIL.Emit(OpCodes.Newobj, interceptorsFieldConstructor); cIL.Emit(OpCodes.Stfld, interceptorsField); } private static ConstructorBuilder CreateConstructorBuilder(TypeBuilder typeBuilder, Type[] parameterTypes) { return typeBuilder.DefineConstructor ( MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.RTSpecialName | MethodAttributes.HideBySig, CallingConventions.Standard, parameterTypes ); } private static Type[] GetParameterTypes(ConstructorInfo constructorInfo) { ParameterInfo[] parameterInfoArray = constructorInfo.GetParameters(); Type[] parameterTypes = new Type[parameterInfoArray.Length]; for (int p = 0; p < parameterInfoArray.Length; p++) { parameterTypes[p] = parameterInfoArray[p].ParameterType; } return parameterTypes; } private static ConstructorInfo CreateInterceptorsFieldConstructor<TBase>() where TBase : class { return ConstructorHelper.CreateGenericConstructorInfo ( typeof(List<>), new Type[] { typeof(IInterceptor<TBase>) }, BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic ); } private static ConstructorInfo CreateDefaultInterceptorConstructor<TBase>() where TBase : class { return ConstructorHelper.CreateGenericConstructorInfo ( typeof(DefaultInterceptor<>), new Type[] { typeof(TBase) }, BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic ); } #endregion } } So, the first two tasks within the class should be fairly clear, we are creating a ConstructorInfo for the interceptorField list and a ConstructorInfo for the DefaultConstructor, this is for instantiating them in each contructor. We then using Reflection get an array of all of the constructors in the base class, we then loop through the array and create a corresponding proxy contructor. Hopefully, the code is fairly easy to follow other than some new types and the dreaded Opcodes. ConstructorBuilder This class defines a new constructor on the type. ILGenerator The ILGenerator allows the use of Reflection.Emit to create the method body. LocalBuilder The local builder allows the storage of data in local variables within a method, in this case it’s the constructed DefaultInterceptor. Constructing the interceptors field The first bit of IL you’ll come across as you follow through the code is the following private method used for constructing the field list of interceptors. private static void ConstructInterceptorsField ( FieldBuilder interceptorsField, ConstructorInfo interceptorsFieldConstructor, ILGenerator cIL ) { cIL.Emit(OpCodes.Ldarg_0); cIL.Emit(OpCodes.Newobj, interceptorsFieldConstructor); cIL.Emit(OpCodes.Stfld, interceptorsField); } The first thing to know about generating code using IL is that you are using a stack, if you want to use something, you need to push it up the stack etc. etc. OpCodes.ldArg_0 This opcode is a really interesting one, basically each method has a hidden first argument of the containing class instance (apart from static classes), constructors are no different. This is the reason you can use syntax like this.myField. So back to the method, as we want to instantiate the List in the interceptorsField, first we need to load the class instance onto the stack, we then load the new object (new List<TBase>) and finally we store it in the interceptorsField. Hopefully, that should follow easily enough in the method. In each constructor you would now have this.interceptors = new List<User<int, IRepository>>(); Constructing and storing the DefaultInterceptor The next bit of code we need to create is the constructed DefaultInterceptor. Firstly, we create a local builder to store the constructed type. Create a local builder LocalBuilder defaultInterceptorMethodVariable = cIL.DeclareLocal(typeof(DefaultInterceptor<>).MakeGenericType(typeof(TBase))); Once our local builder is ready, we then need to construct the DefaultInterceptor<TBase> and store it in the variable. Connstruct DefaultInterceptor private static void ConstructDefaultInterceptor ( ConstructorInfo defaultInterceptorConstructor, ILGenerator cIL, LocalBuilder defaultInterceptorMethodVariable ) { cIL.Emit(OpCodes.Newobj, defaultInterceptorConstructor); cIL.Emit(OpCodes.Stloc, defaultInterceptorMethodVariable); } As you can see, using the ConstructorInfo named defaultInterceptorConstructor, we load the new object onto the stack. Then using the store local opcode (OpCodes.Stloc), we store the new object in the local builder named defaultInterceptorMethodVariable. Add the constructed DefaultInterceptor to the interceptors field collection Using the add method created earlier in this post, we are going to add the new DefaultInterceptor object to the interceptors field collection. Add Default Interceptor private static void AddDefaultInterceptorToInterceptorsList ( FieldBuilder interceptorsField, MethodInfo AddDefaultInterceptor, ILGenerator cIL, LocalBuilder defaultInterceptorMethodVariable ) { cIL.Emit(OpCodes.Ldarg_0); cIL.Emit(OpCodes.Ldfld, interceptorsField); cIL.Emit(OpCodes.Ldloc, defaultInterceptorMethodVariable); cIL.Emit(OpCodes.Callvirt, AddDefaultInterceptor); } So, here’s whats going on. The class instance is first loaded onto the stack using the load argument at index 0 opcode (OpCodes.Ldarg_0) (remember the first arg is the hidden class instance). The interceptorsField is then loaded onto the stack using the load field opcode (OpCodes.Ldfld). We then load the DefaultInterceptor object we stored locally using the load local opcode (OpCodes.Ldloc). Then finally we call the AddDefaultInterceptor method using the call virtual opcode (Opcodes.Callvirt). Completing the constructor The last thing we need to do is complete the constructor. Complete the constructor private static void CreateConstructor(ConstructorInfo constructorInfo, Type[] parameterTypes, ILGenerator cIL) { cIL.Emit(OpCodes.Ldarg_0); if (parameterTypes.Length > 0) { LoadParameterTypes(parameterTypes, cIL); } cIL.Emit(OpCodes.Call, constructorInfo); cIL.Emit(OpCodes.Ret); } private static void LoadParameterTypes(Type[] parameterTypes, ILGenerator cIL) { for (int i = 1; i <= parameterTypes.Length; i++) { cIL.Emit(OpCodes.Ldarg_S, i); } } So, the first thing we do again is load the class instance using the load argument at index 0 opcode (OpCodes.Ldarg_0). We then load each parameter using OpCode.Ldarg_S, this opcode allows us to specify an index position for each argument. We then setup calling the base constructor using OpCodes.Call and the base constructors ConstructorInfo. Finally, all methods are required to return, even when they have a void return. As there are no values on the stack after the OpCodes.Call line, we can safely call the OpCode.Ret to give the constructor a void return. If there was a value, we would have to pop the value of the stack before calling return otherwise, the method would try and return a value. Conclusion This was a slightly hardcore post but hopefully it hasn’t been too hard to follow. The main thing is that a number of the really useful opcodes have been used and now the dynamic proxy is capable of being constructed. If you download the code and debug through the tests at http://rapidioc.codeplex.com/, you’ll be able to create proxies at this point, they cannon do anything in terms of interception but you can happily run the tests, call base methods and properties and also take a look at the created assembly in Reflector. Hope this is useful. The next post should be up soon, it will be covering creating the private methods for calling the base class methods and properties. Kind Regards, Sean.

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Using Durandal to Create Single Page Apps

- by Stephen.Walther

A few days ago, I gave a talk on building Single Page Apps on the Microsoft Stack. In that talk, I recommended that people use Knockout, Sammy, and RequireJS to build their presentation layer and use the ASP.NET Web API to expose data from their server. After I gave the talk, several people contacted me and suggested that I investigate a new open-source JavaScript library named Durandal. Durandal stitches together Knockout, Sammy, and RequireJS to make it easier to use these technologies together. In this blog entry, I want to provide a brief walkthrough of using Durandal to create a simple Single Page App. I am going to demonstrate how you can create a simple Movies App which contains (virtual) pages for viewing a list of movies, adding new movies, and viewing movie details. The goal of this blog entry is to give you a sense of what it is like to build apps with Durandal. Installing Durandal First things first. How do you get Durandal? The GitHub project for Durandal is located here: https://github.com/BlueSpire/Durandal The Wiki — located at the GitHub project — contains all of the current documentation for Durandal. Currently, the documentation is a little sparse, but it is enough to get you started. Instead of downloading the Durandal source from GitHub, a better option for getting started with Durandal is to install one of the Durandal NuGet packages. I built the Movies App described in this blog entry by first creating a new ASP.NET MVC 4 Web Application with the Basic Template. Next, I executed the following command from the Package Manager Console: Install-Package Durandal.StarterKit As you can see from the screenshot of the Package Manager Console above, the Durandal Starter Kit package has several dependencies including: · jQuery · Knockout · Sammy · Twitter Bootstrap The Durandal Starter Kit package includes a sample Durandal application. You can get to the Starter Kit app by navigating to the Durandal controller. Unfortunately, when I first tried to run the Starter Kit app, I got an error because the Starter Kit is hard-coded to use a particular version of jQuery which is already out of date. You can fix this issue by modifying the App_Start\DurandalBundleConfig.cs file so it is jQuery version agnostic like this: bundles.Add( new ScriptBundle("~/scripts/vendor") .Include("~/Scripts/jquery-{version}.js") .Include("~/Scripts/knockout-{version}.js") .Include("~/Scripts/sammy-{version}.js") // .Include("~/Scripts/jquery-1.9.0.min.js") // .Include("~/Scripts/knockout-2.2.1.js") // .Include("~/Scripts/sammy-0.7.4.min.js") .Include("~/Scripts/bootstrap.min.js") ); The recommendation is that you create a Durandal app in a folder off your project root named App. The App folder in the Starter Kit contains the following subfolders and files: · durandal – This folder contains the actual durandal JavaScript library. · viewmodels – This folder contains all of your application’s view models. · views – This folder contains all of your application’s views. · main.js — This file contains all of the JavaScript startup code for your app including the client-side routing configuration. · main-built.js – This file contains an optimized version of your application. You need to build this file by using the RequireJS optimizer (unfortunately, before you can run the optimizer, you must first install NodeJS). For the purpose of this blog entry, I wanted to start from scratch when building the Movies app, so I deleted all of these files and folders except for the durandal folder which contains the durandal library. Creating the ASP.NET MVC Controller and View A Durandal app is built using a single server-side ASP.NET MVC controller and ASP.NET MVC view. A Durandal app is a Single Page App. When you navigate between pages, you are not navigating to new pages on the server. Instead, you are loading new virtual pages into the one-and-only-one server-side view. For the Movies app, I created the following ASP.NET MVC Home controller: public class HomeController : Controller { public ActionResult Index() { return View(); } } There is nothing special about the Home controller – it is as basic as it gets. Next, I created the following server-side ASP.NET view. This is the one-and-only server-side view used by the Movies app: @{ Layout = null; } <!DOCTYPE html> <html> <head> <title>Index</title> </head> <body> <div id="applicationHost"> Loading app.... </div> @Scripts.Render("~/scripts/vendor") <script type="text/javascript" src="~/App/durandal/amd/require.js" data-main="/App/main"></script> </body> </html> Notice that I set the Layout property for the view to the value null. If you neglect to do this, then the default ASP.NET MVC layout will be applied to the view and you will get the <!DOCTYPE> and opening and closing <html> tags twice. Next, notice that the view contains a DIV element with the Id applicationHost. This marks the area where virtual pages are loaded. When you navigate from page to page in a Durandal app, HTML page fragments are retrieved from the server and stuck in the applicationHost DIV element. Inside the applicationHost element, you can place any content which you want to display when a Durandal app is starting up. For example, you can create a fancy splash screen. I opted for simply displaying the text “Loading app…”: Next, notice the view above includes a call to the Scripts.Render() helper. This helper renders out all of the JavaScript files required by the Durandal library such as jQuery and Knockout. Remember to fix the App_Start\DurandalBundleConfig.cs as described above or Durandal will attempt to load an old version of jQuery and throw a JavaScript exception and stop working. Your application JavaScript code is not included in the scripts rendered by the Scripts.Render helper. Your application code is loaded dynamically by RequireJS with the help of the following SCRIPT element located at the bottom of the view: <script type="text/javascript" src="~/App/durandal/amd/require.js" data-main="/App/main"></script> The data-main attribute on the SCRIPT element causes RequireJS to load your /app/main.js JavaScript file to kick-off your Durandal app. Creating the Durandal Main.js File The Durandal Main.js JavaScript file, located in your App folder, contains all of the code required to configure the behavior of Durandal. Here’s what the Main.js file looks like in the case of the Movies app: require.config({ paths: { 'text': 'durandal/amd/text' } }); define(function (require) { var app = require('durandal/app'), viewLocator = require('durandal/viewLocator'), system = require('durandal/system'), router = require('durandal/plugins/router'); //>>excludeStart("build", true); system.debug(true); //>>excludeEnd("build"); app.start().then(function () { //Replace 'viewmodels' in the moduleId with 'views' to locate the view. //Look for partial views in a 'views' folder in the root. viewLocator.useConvention(); //configure routing router.useConvention(); router.mapNav("movies/show"); router.mapNav("movies/add"); router.mapNav("movies/details/:id"); app.adaptToDevice(); //Show the app by setting the root view model for our application with a transition. app.setRoot('viewmodels/shell', 'entrance'); }); }); There are three important things to notice about the main.js file above. First, notice that it contains a section which enables debugging which looks like this: //>>excludeStart(“build”, true); system.debug(true); //>>excludeEnd(“build”); This code enables debugging for your Durandal app which is very useful when things go wrong. When you call system.debug(true), Durandal writes out debugging information to your browser JavaScript console. For example, you can use the debugging information to diagnose issues with your client-side routes: (The funny looking //> symbols around the system.debug() call are RequireJS optimizer pragmas). The main.js file is also the place where you configure your client-side routes. In the case of the Movies app, the main.js file is used to configure routes for three page: the movies show, add, and details pages. //configure routing router.useConvention(); router.mapNav("movies/show"); router.mapNav("movies/add"); router.mapNav("movies/details/:id"); The route for movie details includes a route parameter named id. Later, we will use the id parameter to lookup and display the details for the right movie. Finally, the main.js file above contains the following line of code: //Show the app by setting the root view model for our application with a transition. app.setRoot('viewmodels/shell', 'entrance'); This line of code causes Durandal to load up a JavaScript file named shell.js and an HTML fragment named shell.html. I’ll discuss the shell in the next section. Creating the Durandal Shell You can think of the Durandal shell as the layout or master page for a Durandal app. The shell is where you put all of the content which you want to remain constant as a user navigates from virtual page to virtual page. For example, the shell is a great place to put your website logo and navigation links. The Durandal shell is composed from two parts: a JavaScript file and an HTML file. Here’s what the HTML file looks like for the Movies app: <h1>Movies App</h1> <div class="container-fluid page-host">  </div> And here is what the JavaScript file looks like: define(function (require) { var router = require('durandal/plugins/router'); return { router: router, activate: function () { return router.activate('movies/show'); } }; }); The JavaScript file contains the view model for the shell. This view model returns the Durandal router so you can access the list of configured routes from your shell. Notice that the JavaScript file includes a function named activate(). This function loads the movies/show page as the first page in the Movies app. If you want to create a different default Durandal page, then pass the name of a different age to the router.activate() method. Creating the Movies Show Page Durandal pages are created out of a view model and a view. The view model contains all of the data and view logic required for the view. The view contains all of the HTML markup for rendering the view model. Let’s start with the movies show page. The movies show page displays a list of movies. The view model for the show page looks like this: define(function (require) { var moviesRepository = require("repositories/moviesRepository"); return { movies: ko.observable(), activate: function() { this.movies(moviesRepository.listMovies()); } }; }); You create a view model by defining a new RequireJS module (see http://requirejs.org). You create a RequireJS module by placing all of your JavaScript code into an anonymous function passed to the RequireJS define() method. A RequireJS module has two parts. You retrieve all of the modules which your module requires at the top of your module. The code above depends on another RequireJS module named repositories/moviesRepository. Next, you return the implementation of your module. The code above returns a JavaScript object which contains a property named movies and a method named activate. The activate() method is a magic method which Durandal calls whenever it activates your view model. Your view model is activated whenever you navigate to a page which uses it. In the code above, the activate() method is used to get the list of movies from the movies repository and assign the list to the view model movies property. The HTML for the movies show page looks like this: <table> <thead> <tr> <th>Title</th><th>Director</th> </tr> </thead> <tbody data-bind="foreach:movies"> <tr> <td data-bind="text:title"></td> <td data-bind="text:director"></td> <td><a data-bind="attr:{href:'#/movies/details/'+id}">Details</a></td> </tr> </tbody> </table> <a href="#/movies/add">Add Movie</a> Notice that this is an HTML fragment. This fragment will be stuffed into the page-host DIV element in the shell.html file which is stuffed, in turn, into the applicationHost DIV element in the server-side MVC view. The HTML markup above contains data-bind attributes used by Knockout to display the list of movies (To learn more about Knockout, visit http://knockoutjs.com). The list of movies from the view model is displayed in an HTML table. Notice that the page includes a link to a page for adding a new movie. The link uses the following URL which starts with a hash: #/movies/add. Because the link starts with a hash, clicking the link does not cause a request back to the server. Instead, you navigate to the movies/add page virtually. Creating the Movies Add Page The movies add page also consists of a view model and view. The add page enables you to add a new movie to the movie database. Here’s the view model for the add page: define(function (require) { var app = require('durandal/app'); var router = require('durandal/plugins/router'); var moviesRepository = require("repositories/moviesRepository"); return { movieToAdd: { title: ko.observable(), director: ko.observable() }, activate: function () { this.movieToAdd.title(""); this.movieToAdd.director(""); this._movieAdded = false; }, canDeactivate: function () { if (this._movieAdded == false) { return app.showMessage('Are you sure you want to leave this page?', 'Navigate', ['Yes', 'No']); } else { return true; } }, addMovie: function () { // Add movie to db moviesRepository.addMovie(ko.toJS(this.movieToAdd)); // flag new movie this._movieAdded = true; // return to list of movies router.navigateTo("#/movies/show"); } }; }); The view model contains one property named movieToAdd which is bound to the add movie form. The view model also has the following three methods: 1. activate() – This method is called by Durandal when you navigate to the add movie page. The activate() method resets the add movie form by clearing out the movie title and director properties. 2. canDeactivate() – This method is called by Durandal when you attempt to navigate away from the add movie page. If you return false then navigation is cancelled. 3. addMovie() – This method executes when the add movie form is submitted. This code adds the new movie to the movie repository. I really like the Durandal canDeactivate() method. In the code above, I use the canDeactivate() method to show a warning to a user if they navigate away from the add movie page – either by clicking the Cancel button or by hitting the browser back button – before submitting the add movie form: The view for the add movie page looks like this: <form data-bind="submit:addMovie"> <fieldset> <legend>Add Movie</legend> <div> <label> Title: <input data-bind="value:movieToAdd.title" required /> </label> </div> <div> <label> Director: <input data-bind="value:movieToAdd.director" required /> </label> </div> <div> <input type="submit" value="Add" /> <a href="#/movies/show">Cancel</a> </div> </fieldset> </form> I am using Knockout to bind the movieToAdd property from the view model to the INPUT elements of the HTML form. Notice that the FORM element includes a data-bind attribute which invokes the addMovie() method from the view model when the HTML form is submitted. Creating the Movies Details Page You navigate to the movies details Page by clicking the Details link which appears next to each movie in the movies show page: The Details links pass the movie ids to the details page: #/movies/details/0 #/movies/details/1 #/movies/details/2 Here’s what the view model for the movies details page looks like: define(function (require) { var router = require('durandal/plugins/router'); var moviesRepository = require("repositories/moviesRepository"); return { movieToShow: { title: ko.observable(), director: ko.observable() }, activate: function (context) { // Grab movie from repository var movie = moviesRepository.getMovie(context.id); // Add to view model this.movieToShow.title(movie.title); this.movieToShow.director(movie.director); } }; }); Notice that the view model activate() method accepts a parameter named context. You can take advantage of the context parameter to retrieve route parameters such as the movie Id. In the code above, the context.id property is used to retrieve the correct movie from the movie repository and the movie is assigned to a property named movieToShow exposed by the view model. The movie details view displays the movieToShow property by taking advantage of Knockout bindings: <div> <h2 data-bind="text:movieToShow.title"></h2> directed by <span data-bind="text:movieToShow.director"></span> </div> Summary The goal of this blog entry was to walkthrough building a simple Single Page App using Durandal and to get a feel for what it is like to use this library. I really like how Durandal stitches together Knockout, Sammy, and RequireJS and establishes patterns for using these libraries to build Single Page Apps. Having a standard pattern which developers on a team can use to build new pages is super valuable. Once you get the hang of it, using Durandal to create new virtual pages is dead simple. Just define a new route, view model, and view and you are done. I also appreciate the fact that Durandal did not attempt to re-invent the wheel and that Durandal leverages existing JavaScript libraries such as Knockout, RequireJS, and Sammy. These existing libraries are powerful libraries and I have already invested a considerable amount of time in learning how to use them. Durandal makes it easier to use these libraries together without losing any of their power. Durandal has some additional interesting features which I have not had a chance to play with yet. For example, you can use the RequireJS optimizer to combine and minify all of a Durandal app’s code. Also, Durandal supports a way to create custom widgets (client-side controls) by composing widgets from a controller and view. You can download the code for the Movies app by clicking the following link (this is a Visual Studio 2012 project): Durandal Movie App

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Creating STA COM compatible ASP.NET Applications

- by Rick Strahl

When building ASP.NET applications that interface with old school COM objects like those created with VB6 or Visual FoxPro (MTDLL), it's extremely important that the threads that are serving requests use Single Threaded Apartment Threading. STA is a COM built-in technology that allows essentially single threaded components to operate reliably in a multi-threaded environment. STA's guarantee that COM objects instantiated on a specific thread stay on that specific thread and any access to a COM object from another thread automatically marshals that thread to the STA thread. The end effect is that you can have multiple threads, but a COM object instance lives on a fixed never changing thread. ASP.NET by default uses MTA (multi-threaded apartment) threads which are truly free spinning threads that pay no heed to COM object marshaling. This is vastly more efficient than STA threading which has a bit of overhead in determining whether it's OK to run code on a given thread or whether some sort of thread/COM marshaling needs to occur. MTA COM components can be very efficient, but STA COM components in a multi-threaded environment always tend to have a fair amount of overhead. It's amazing how much COM Interop I still see today so while it seems really old school to be talking about this topic, it's actually quite apropos for me as I have many customers using legacy COM systems that need to interface with other .NET applications. In this post I'm consolidating some of the hacks I've used to integrate with various ASP.NET technologies when using STA COM Components. STA in ASP.NET Support for STA threading in the ASP.NET framework is fairly limited. Specifically only the original ASP.NET WebForms technology supports STA threading directly via its STA Page Handler implementation or what you might know as ASPCOMPAT mode. For WebForms running STA components is as easy as specifying the ASPCOMPAT attribute in the @Page tag:<%@ Page Language="C#" AspCompat="true" %> which runs the page in STA mode. Removing it runs in MTA mode. Simple. Unfortunately all other ASP.NET technologies built on top of the core ASP.NET engine do not support STA natively. So if you want to use STA COM components in MVC or with class ASMX Web Services, there's no automatic way like the ASPCOMPAT keyword available. So what happens when you run an STA COM component in an MTA application? In low volume environments - nothing much will happen. The COM objects will appear to work just fine as there are no simultaneous thread interactions and the COM component will happily run on a single thread or multiple single threads one at a time. So for testing running components in MTA environments may appear to work just fine. However as load increases and threads get re-used by ASP.NET COM objects will end up getting created on multiple different threads. This can result in crashes or hangs, or data corruption in the STA components which store their state in thread local storage on the STA thread. If threads overlap this global store can easily get corrupted which in turn causes problems. STA ensures that any COM object instance loaded always stays on the same thread it was instantiated on. What about COM+? COM+ is supposed to address the problem of STA in MTA applications by providing an abstraction with it's own thread pool manager for COM objects. It steps in to the COM instantiation pipeline and hands out COM instances from its own internally maintained STA Thread pool. This guarantees that the COM instantiation threads are STA threads if using STA components. COM+ works, but in my experience the technology is very, very slow for STA components. It adds a ton of overhead and reduces COM performance noticably in load tests in IIS. COM+ can make sense in some situations but for Web apps with STA components it falls short. In addition there's also the need to ensure that COM+ is set up and configured on the target machine and the fact that components have to be registered in COM+. COM+ also keeps components up at all times, so if a component needs to be replaced the COM+ package needs to be unloaded (same is true for IIS hosted components but it's more common to manage that). COM+ is an option for well established components, but native STA support tends to provide better performance and more consistent usability, IMHO. STA for non supporting ASP.NET Technologies As mentioned above only WebForms supports STA natively. However, by utilizing the WebForms ASP.NET Page handler internally it's actually possible to trick various other ASP.NET technologies and let them work with STA components. This is ugly but I've used each of these in various applications and I've had minimal problems making them work with FoxPro STA COM components which is about as dififcult as it gets for COM Interop in .NET. In this post I summarize several STA workarounds that enable you to use STA threading with these ASP.NET Technologies: ASMX Web Services ASP.NET MVC WCF Web Services ASP.NET Web API ASMX Web Services I start with classic ASP.NET ASMX Web Services because it's the easiest mechanism that allows for STA modification. It also clearly demonstrates how the WebForms STA Page Handler is the key technology to enable the various other solutions to create STA components. Essentially the way this works is to override the WebForms Page class and hijack it's init functionality for processing requests. Here's what this looks like for Web Services:namespace FoxProAspNet { public class WebServiceStaHandler : System.Web.UI.Page, IHttpAsyncHandler { protected override void OnInit(EventArgs e) { IHttpHandler handler = new WebServiceHandlerFactory().GetHandler( this.Context, this.Context.Request.HttpMethod, this.Context.Request.FilePath, this.Context.Request.PhysicalPath); handler.ProcessRequest(this.Context); this.Context.ApplicationInstance.CompleteRequest(); } public IAsyncResult BeginProcessRequest( HttpContext context, AsyncCallback cb, object extraData) { return this.AspCompatBeginProcessRequest(context, cb, extraData); } public void EndProcessRequest(IAsyncResult result) { this.AspCompatEndProcessRequest(result); } } public class AspCompatWebServiceStaHandlerWithSessionState : WebServiceStaHandler, IRequiresSessionState { } } This class overrides the ASP.NET WebForms Page class which has a little known AspCompatBeginProcessRequest() and AspCompatEndProcessRequest() method that is responsible for providing the WebForms ASPCOMPAT functionality. These methods handle routing requests to STA threads. Note there are two classes - one that includes session state and one that does not. If you plan on using ASP.NET Session state use the latter class, otherwise stick to the former. This maps to the EnableSessionState page setting in WebForms. This class simply hooks into this functionality by overriding the BeginProcessRequest and EndProcessRequest methods and always forcing it into the AspCompat methods. The way this works is that BeginProcessRequest() fires first to set up the threads and starts intializing the handler. As part of that process the OnInit() method is fired which is now already running on an STA thread. The code then creates an instance of the actual WebService handler factory and calls its ProcessRequest method to start executing which generates the Web Service result. Immediately after ProcessRequest the request is stopped with Application.CompletRequest() which ensures that the rest of the Page handler logic doesn't fire. This means that even though the fairly heavy Page class is overridden here, it doesn't end up executing any of its internal processing which makes this code fairly efficient. In a nutshell, we're highjacking the Page HttpHandler and forcing it to process the WebService process handler in the context of the AspCompat handler behavior. Hooking up the Handler Because the above is an HttpHandler implementation you need to hook up the custom handler and replace the standard ASMX handler. To do this you need to modify the web.config file (here for IIS 7 and IIS Express): <configuration> <system.webServer> <handlers> <remove name="WebServiceHandlerFactory-Integrated-4.0" /> <add name="Asmx STA Web Service Handler" path="*.asmx" verb="*" type="FoxProAspNet.WebServiceStaHandler" precondition="integrated"/> </handlers> </system.webServer> </configuration> (Note: The name for the WebServiceHandlerFactory-Integrated-4.0 might be slightly different depending on your server version. Check the IIS Handler configuration in the IIS Management Console for the exact name or simply remove the handler from the list there which will propagate to your web.config). For IIS 5 & 6 (Windows XP/2003) or the Visual Studio Web Server use:<configuration> <system.web> <httpHandlers> <remove path="*.asmx" verb="*" /> <add path="*.asmx" verb="*" type="FoxProAspNet.WebServiceStaHandler" /> </httpHandlers> </system.web></configuration> To test, create a new ASMX Web Service and create a method like this: [WebService(Namespace = "http://foxaspnet.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] public class FoxWebService : System.Web.Services.WebService { [WebMethod] public string HelloWorld() { return "Hello World. Threading mode is: " + System.Threading.Thread.CurrentThread.GetApartmentState(); } } Run this before you put in the web.config configuration changes and you should get: Hello World. Threading mode is: MTA Then put the handler mapping into Web.config and you should see: Hello World. Threading mode is: STA And you're on your way to using STA COM components. It's a hack but it works well! I've used this with several high volume Web Service installations with various customers and it's been fast and reliable. ASP.NET MVC ASP.NET MVC has quickly become the most popular ASP.NET technology, replacing WebForms for creating HTML output. MVC is more complex to get started with, but once you understand the basic structure of how requests flow through the MVC pipeline it's easy to use and amazingly flexible in manipulating HTML requests. In addition, MVC has great support for non-HTML output sources like JSON and XML, making it an excellent choice for AJAX requests without any additional tools. Unlike WebForms ASP.NET MVC doesn't support STA threads natively and so some trickery is needed to make it work with STA threads as well. MVC gets its handler implementation through custom route handlers using ASP.NET's built in routing semantics. To work in an STA handler requires working in the Page Handler as part of the Route Handler implementation. As with the Web Service handler the first step is to create a custom HttpHandler that can instantiate an MVC request pipeline properly:public class MvcStaThreadHttpAsyncHandler : Page, IHttpAsyncHandler, IRequiresSessionState { private RequestContext _requestContext; public MvcStaThreadHttpAsyncHandler(RequestContext requestContext) { if (requestContext == null) throw new ArgumentNullException("requestContext"); _requestContext = requestContext; } public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData) { return this.AspCompatBeginProcessRequest(context, cb, extraData); } protected override void OnInit(EventArgs e) { var controllerName = _requestContext.RouteData.GetRequiredString("controller"); var controllerFactory = ControllerBuilder.Current.GetControllerFactory(); var controller = controllerFactory.CreateController(_requestContext, controllerName); if (controller == null) throw new InvalidOperationException("Could not find controller: " + controllerName); try { controller.Execute(_requestContext); } finally { controllerFactory.ReleaseController(controller); } this.Context.ApplicationInstance.CompleteRequest(); } public void EndProcessRequest(IAsyncResult result) { this.AspCompatEndProcessRequest(result); } public override void ProcessRequest(HttpContext httpContext) { throw new NotSupportedException("STAThreadRouteHandler does not support ProcessRequest called (only BeginProcessRequest)"); } } This handler code figures out which controller to load and then executes the controller. MVC internally provides the information needed to route to the appropriate method and pass the right parameters. Like the Web Service handler the logic occurs in the OnInit() and performs all the processing in that part of the request. Next, we need a RouteHandler that can actually pick up this handler. Unlike the Web Service handler where we simply registered the handler, MVC requires a RouteHandler to pick up the handler. RouteHandlers look at the URL's path and based on that decide on what handler to invoke. The route handler is pretty simple - all it does is load our custom handler: public class MvcStaThreadRouteHandler : IRouteHandler { public IHttpHandler GetHttpHandler(RequestContext requestContext) { if (requestContext == null) throw new ArgumentNullException("requestContext"); return new MvcStaThreadHttpAsyncHandler(requestContext); } } At this point you can instantiate this route handler and force STA requests to MVC by specifying a route. The following sets up the ASP.NET Default Route:Route mvcRoute = new Route("{controller}/{action}/{id}", new RouteValueDictionary( new { controller = "Home", action = "Index", id = UrlParameter.Optional }), new MvcStaThreadRouteHandler()); RouteTable.Routes.Add(mvcRoute); To make this code a little easier to work with and mimic the behavior of the routes.MapRoute() functionality extension method that MVC provides, here is an extension method for MapMvcStaRoute(): public static class RouteCollectionExtensions { public static void MapMvcStaRoute(this RouteCollection routeTable, string name, string url, object defaults = null) { Route mvcRoute = new Route(url, new RouteValueDictionary(defaults), new MvcStaThreadRouteHandler()); RouteTable.Routes.Add(mvcRoute); } } With this the syntax to add route becomes a little easier and matches the MapRoute() method:RouteTable.Routes.MapMvcStaRoute( name: "Default", url: "{controller}/{action}/{id}", defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional } ); The nice thing about this route handler, STA Handler and extension method is that it's fully self contained. You can put all three into a single class file and stick it into your Web app, and then simply call MapMvcStaRoute() and it just works. Easy! To see whether this works create an MVC controller like this: public class ThreadTestController : Controller { public string ThreadingMode() { return Thread.CurrentThread.GetApartmentState().ToString(); } } Try this test both with only the MapRoute() hookup in the RouteConfiguration in which case you should get MTA as the value. Then change the MapRoute() call to MapMvcStaRoute() leaving all the parameters the same and re-run the request. You now should see STA as the result. You're on your way using STA COM components reliably in ASP.NET MVC. WCF Web Services running through IIS WCF Web Services provide a more robust and wider range of services for Web Services. You can use WCF over HTTP, TCP, and Pipes, and WCF services support WS* secure services. There are many features in WCF that go way beyond what ASMX can do. But it's also a bit more complex than ASMX. As a basic rule if you need to serve straight SOAP Services over HTTP I 'd recommend sticking with the simpler ASMX services especially if COM is involved. If you need WS* support or want to serve data over non-HTTP protocols then WCF makes more sense. WCF is not my forte but I found a solution from Scott Seely on his blog that describes the progress and that seems to work well. I'm copying his code below so this STA information is all in one place and quickly explain. Scott's code basically works by creating a custom OperationBehavior which can be specified via an [STAOperation] attribute on every method. Using his attribute you end up with a class (or Interface if you separate the contract and class) that looks like this: [ServiceContract] public class WcfService { [OperationContract] public string HelloWorldMta() { return Thread.CurrentThread.GetApartmentState().ToString(); } // Make sure you use this custom STAOperationBehavior // attribute to force STA operation of service methods [STAOperationBehavior] [OperationContract] public string HelloWorldSta() { return Thread.CurrentThread.GetApartmentState().ToString(); } } Pretty straight forward. The latter method returns STA while the former returns MTA. To make STA work every method needs to be marked up. The implementation consists of the attribute and OperationInvoker implementation. Here are the two classes required to make this work from Scott's post:public class STAOperationBehaviorAttribute : Attribute, IOperationBehavior { public void AddBindingParameters(OperationDescription operationDescription, System.ServiceModel.Channels.BindingParameterCollection bindingParameters) { } public void ApplyClientBehavior(OperationDescription operationDescription, System.ServiceModel.Dispatcher.ClientOperation clientOperation) { // If this is applied on the client, well, it just doesn’t make sense. // Don’t throw in case this attribute was applied on the contract // instead of the implementation. } public void ApplyDispatchBehavior(OperationDescription operationDescription, System.ServiceModel.Dispatcher.DispatchOperation dispatchOperation) { // Change the IOperationInvoker for this operation. dispatchOperation.Invoker = new STAOperationInvoker(dispatchOperation.Invoker); } public void Validate(OperationDescription operationDescription) { if (operationDescription.SyncMethod == null) { throw new InvalidOperationException("The STAOperationBehaviorAttribute " + "only works for synchronous method invocations."); } } } public class STAOperationInvoker : IOperationInvoker { IOperationInvoker _innerInvoker; public STAOperationInvoker(IOperationInvoker invoker) { _innerInvoker = invoker; } public object[] AllocateInputs() { return _innerInvoker.AllocateInputs(); } public object Invoke(object instance, object[] inputs, out object[] outputs) { // Create a new, STA thread object[] staOutputs = null; object retval = null; Thread thread = new Thread( delegate() { retval = _innerInvoker.Invoke(instance, inputs, out staOutputs); }); thread.SetApartmentState(ApartmentState.STA); thread.Start(); thread.Join(); outputs = staOutputs; return retval; } public IAsyncResult InvokeBegin(object instance, object[] inputs, AsyncCallback callback, object state) { // We don’t handle async… throw new NotImplementedException(); } public object InvokeEnd(object instance, out object[] outputs, IAsyncResult result) { // We don’t handle async… throw new NotImplementedException(); } public bool IsSynchronous { get { return true; } } } The key in this setup is the Invoker and the Invoke method which creates a new thread and then fires the request on this new thread. Because this approach creates a new thread for every request it's not super efficient. There's a bunch of overhead involved in creating the thread and throwing it away after each thread, but it'll work for low volume requests and insure each thread runs in STA mode. If better performance is required it would be useful to create a custom thread manager that can pool a number of STA threads and hand off threads as needed rather than creating new threads on every request. If your Web Service needs are simple and you need only to serve standard SOAP 1.x requests, I would recommend sticking with ASMX services. It's easier to set up and work with and for STA component use it'll be significantly better performing since ASP.NET manages the STA thread pool for you rather than firing new threads for each request. One nice thing about Scotts code is though that it works in any WCF environment including self hosting. It has no dependency on ASP.NET or WebForms for that matter. STA - If you must STA components are a pain in the ass and thankfully there isn't too much stuff out there anymore that requires it. But when you need it and you need to access STA functionality from .NET at least there are a few options available to make it happen. Each of these solutions is a bit hacky, but they work - I've used all of them in production with good results with FoxPro components. I hope compiling all of these in one place here makes it STA consumption a little bit easier. I feel your pain :-) Resources Download STA Handler Code Examples Scott Seely's original STA WCF OperationBehavior Article© Rick Strahl, West Wind Technologies, 2005-2012Posted in FoxPro ASP.NET .NET COM Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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Extending Currying: Partial Functions in Javascript

- by kerry

Last week I posted about function currying in javascript. This week I am taking it a step further by adding the ability to call partial functions. Suppose we have a graphing application that will pull data via Ajax and perform some calculation to update a graph. Using a method with the signature ‘updateGraph(id,value)’. To do this, we have do something like this: 1: for(var i=0;i<objects.length;i++) { 2: Ajax.request('/some/data',{id:objects[i].id},function(json) { 3: updateGraph(json.id, json.value); 4: } 5: } This works fine. But, using this method we need to return the id in the json response from the server. This works fine, but is not that elegant and increase network traffic. Using partial function currying we can bind the id parameter and add the second parameter later (when returning from the asynchronous call). To do this, we will need the updated curry method. I have added support for sending additional parameters at runtime for curried methods. 1: Function.prototype.curry = function(scope) { 2: scope = scope || window 3: var args = []; 4: for (var i=1, len = arguments.length; i < len; ++i) { 5: args.push(arguments[i]); 6: } 7: var m = this; 8: return function() { 9: for (var i=0, len = arguments.length; i < len; ++i) { 10: args.push(arguments[i]); 11: } 12: return m.apply(scope, args); 13: }; 14: } To partially curry this method we will call the curry method with the id parameter, then the request will callback on it with just the value. Any additional parameters are appended to the method call. 1: for(var i=0;i<objects.length;i++) { 2: var id=objects[i].id; 3: Ajax.request('/some/data',{id: id}, updateGraph.curry(id)); 4: } As you can see, partial currying gives is a very useful tool and this simple method should be a part of every developer’s toolbox.

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Java Dynamic Binding

- by Chris Okyen

I am having trouble understanding the OOP Polymorphic principl of Dynamic Binding ( Late Binding ) in Java. I looked for question pertaining to java, and wasn't sure if a overall answer to how dynamic binding works would pertain to Java Dynamic Binding, I wrote this question. Given: class Person { private String name; Person(intitialName) { name = initialName; } // irrelevant methods is here. // Overides Objects method public void writeOutput() { println(name); } } class Student extends Person { private int studentNumber; Student(String intitialName, int initialStudentNumber) { super(intitialName); studentNumber = initialStudentNumber; } // irrellevant methods here... // overides Person, Student and Objects method public void writeOutput() { super.writeOutput(); println(studentNumber); } } class Undergaraduate extends Student { private int level; Undergraduate(String intitialName, int initialStudentNumber,int initialLevel) { super(intitialName,initialStudentNumber); level = initialLevel; } // irrelevant methods is here. // overides Person, Student and Objects method public void writeOutput() { super.writeOutput(); println(level); } } I am wondering. if I had an array called person declared to contain objects of type Person: Person[] people = new Person[2]; person[0] = new Undergraduate("Cotty, Manny",4910,1); person[1] = new Student("DeBanque, Robin", 8812); Given that person[] is declared to be of type Person, you would expect, for example, in the third line where person[0] is initialized to a new Undergraduate object,to only gain the instance variable from Person and Persons Methods since doesn't the assignment to a new Undergraduate to it's ancestor denote the Undergraduate object to access Person - it's Ancestors, methods and isntance variables... Thus ...with the following code I would expect person[0].writeOutput(); // calls Undergraduate::writeOutput() person[1].writeOutput(); // calls Student::writeOutput() person[0] to not have Undergraduate's writeOutput() overidden method, nor have person[1] to have Student's overidden method - writeOutput(). If I had Person mikeJones = new Student("Who?,MikeJones",44,4); mikeJones.writeOutput(); The Person::writeOutput() method would be called. Why is this not so? Does it have to do with something I don't understand about relating to arrays? Does the declaration Person[] people = new Person[2] not bind the method like the previous code would?

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Calling functions from different classes

- by A Ron Hubbard Clevenger

I'm writing a program and I'm supposed to check and see if a certain object is in the list before I call it. I set up the contains() method which is supposed to use the equals() method of the Comparable interface I implemented on my Golfer class but it doesn't seem to call it (I put print statements in to check). I can't seem to figure out whats wrong with the code, the ArrayUnsortedList class I'm using to go through the list even uses the correct toString() method I defined in my Golfer class but for some reason it won't use the equals() method I implemented. //From "GolfApp.java" public class GolfApp{ ListInterface <Golfer>golfers = new ArraySortedList<Golfer> (20); Golfer golfer; //..*snip*.. if(this.golfers.contains(new Golfer(name,score))) System.out.println("The list already contains this golfer"); else{ this.golfers.add(this.golfer = new Golfer(name,score)); System.out.println("This golfer is already on the list"); } //From "ArrayUnsortedList.java" protected void find(T target){ location = 0; found = false; while (location < numElements){ if (list[location].equals(target)) //Where I think the problem is { found = true; return; } else location++; } } public boolean contains(T element){ find(element); return found; } //From "Golfer.java" public class Golfer implements Comparable<Golfer>{ //..irrelavant code sniped..// public boolean equals(Golfer golfer) { String thisString = score + ":" + name; String otherString = golfer.getScore() + ":" + golfer.getName() ; System.out.println("Golfer.equals() has bee called"); return thisString.equalsIgnoreCase(otherString); } public String toString() { return (score + ":" + name); } My main problem seems to be getting the find function of the ArrayUnsortedList to call my equals function in the find() part of the List but I'm not exactly sure why, like I said when I have it printed out it works with the toString() method I implemented perfectly. I'm almost positive the problem has to do with the find() function in the ArraySortedList not calling my equals() method. I tried using some other functions that relied on the find() method and got the same results.

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What is the best strategy for licensing a desktop application using a web service, when all I need to know is when people use the product?

- by user1667022

Our company's main application is a desktop program that is used at warehouses and written in C# and Windows Presentation Forms. The next thing we want to be able to do is track when customers open up the application and when it is being used. The reason for this is so we can charge them per month, based on if they are/arn't using the application. My boss is having me research different ways to "license" the product under these requirements. Not having any experience doing this, a few things come to mind. I could create a web application that runs on a server, and every time the desktop application is opened and the user logs in, the application connects to the server and marks a database with the DateTime. Or is there licensing software that I can use to accomplish this? Just looking for tips/advice from people who have experience with this type of stuff.

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Parallelism in .NET – Part 20, Using Task with Existing APIs

- by Reed

Although the Task class provides a huge amount of flexibility for handling asynchronous actions, the .NET Framework still contains a large number of APIs that are based on the previous asynchronous programming model. While Task and Task<T> provide a much nicer syntax as well as extending the flexibility, allowing features such as continuations based on multiple tasks, the existing APIs don’t directly support this workflow. There is a method in the TaskFactory class which can be used to adapt the existing APIs to the new Task class: TaskFactory.FromAsync. This method provides a way to convert from the BeginOperation/EndOperation method pair syntax common through .NET Framework directly to a Task<T> containing the results of the operation in the task’s Result parameter. While this method does exist, it unfortunately comes at a cost – the method overloads are far from simple to decipher, and the resulting code is not always as easily understood as newer code based directly on the Task class. For example, a single call to handle WebRequest.BeginGetResponse/EndGetReponse, one of the easiest “pairs” of methods to use, looks like the following: var task = Task.Factory.FromAsync<WebResponse>( request.BeginGetResponse, request.EndGetResponse, null); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The compiler is unfortunately unable to infer the correct type, and, as a result, the WebReponse must be explicitly mentioned in the method call. As a result, I typically recommend wrapping this into an extension method to ease use. For example, I would place the above in an extension method like: public static class WebRequestExtensions { public static Task<WebResponse> GetReponseAsync(this WebRequest request) { return Task.Factory.FromAsync<WebResponse>( request.BeginGetResponse, request.EndGetResponse, null); } } This dramatically simplifies usage. For example, if we wanted to asynchronously check to see if this blog supported XHTML 1.0, and report that in a text box to the user, we could do: var webRequest = WebRequest.Create("http://www.reedcopsey.com"); webRequest.GetReponseAsync().ContinueWith(t => { using (var sr = new StreamReader(t.Result.GetResponseStream())) { string str = sr.ReadLine();; this.textBox1.Text = string.Format("Page at {0} supports XHTML 1.0: {1}", t.Result.ResponseUri, str.Contains("XHTML 1.0")); } }, TaskScheduler.FromCurrentSynchronizationContext()); By using a continuation with a TaskScheduler based on the current synchronization context, we can keep this request asynchronous, check based on the first line of the response string, and report the results back on our UI directly.

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How to remove window applet from Gnome3?

- by Filip Nowak

I installed today window applet for Gnome3 from this webupd8 post. The effect of the installation shown in the picture. I tried apt-get remove --purge and nothing happens. How do I remove this window applet? http://i.stack.imgur.com/D1s9b.jpg When i try metacity --replace &unity [1] 3171 Checking if settings need to be migrated ...no Checking if internal files need to be migrated ...no Backend : gconf Integration : true Profile : default Adding plugins Skipping upgrade com.canonical.unity.unity.01.upgrade Skipping upgrade com.canonical.unity.unity.02.upgrade Initializing core options...done Initializing bailer options...done Initializing detection options...done Initializing composite options...done Initializing opengl options...done Initializing decor options...done Initializing move options...done Initializing vpswitch options...done Initializing gnomecompat options...done Initializing grid options...done Initializing mousepoll options...done Initializing place options...done Initializing resize options...done Initializing animation options...done Initializing wall options...done Initializing session options...done Initializing workarounds options...done Initializing wobbly options...done compiz (expo) - Warn: failed to bind image to texture Initializing expo options...done Initializing ezoom options...done Initializing staticswitcher options...done Initializing fade options...done Initializing scale options...done Screen geometry changed: 0x0x1920x1080 Initializing unityshell options...done DEBUG 2012-02-19 21:22:40 glib <unknown>:0 Setting to primary screen rect: x=0 y=0 w=1920 h=1080 WARN 2012-02-19 21:22:40 unity.favorites FavoriteStoreGSettings.cpp:138 Unable to load GDesktopAppInfo for 'bluefish.desktop' WARN 2012-02-19 21:22:40 unity.favorites FavoriteStoreGSettings.cpp:138 Unable to load GDesktopAppInfo for 'filezilla.desktop' WARN 2012-02-19 21:22:40 unity.favorites FavoriteStoreGSettings.cpp:138 Unable to load GDesktopAppInfo for 'gimp.desktop' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' WARN 2012-02-19 21:22:40 glib.glib-gobject <unknown>:0 invalid cast from `BamfWindow' to `BamfApplication' Setting Update "texture_filter" Setting Update "sync_to_vblank" Setting Update "fullscreen_visual_bell" Setting Update "panel_opacity" Setting Update "launcher_opacity" Setting Update "icon_size" WARN 2012-02-19 21:23:32 unity.glib.dbusproxy GLibDBusProxy.cpp:255 Cannot call method InfoRequest proxy /com/canonical/unity/lens/applications does not exist WARN 2012-02-19 21:23:32 unity.glib.dbusproxy GLibDBusProxy.cpp:255 Cannot call method SetActive proxy /com/canonical/unity/lens/applications does not exist WARN 2012-02-19 21:23:32 unity.glib.dbusproxy GLibDBusProxy.cpp:255 Cannot call method InfoRequest proxy /com/canonical/unity/lens/commands does not exist WARN 2012-02-19 21:23:32 unity.glib.dbusproxy GLibDBusProxy.cpp:255 Cannot call method SetActive proxy /com/canonical/unity/lens/commands does not exist WARN 2012-02-19 21:23:32 unity.glib.dbusproxy GLibDBusProxy.cpp:255 Cannot call method InfoRequest proxy /com/canonical/unity/lens/files does not exist WARN 2012-02-19 21:23:32 unity.glib.dbusproxy GLibDBusProxy.cpp:255 Cannot call method SetActive proxy /com/canonical/unity/lens/files does not exist WARN 2012-02-19 21:23:32 unity.glib.dbusproxy GLibDBusProxy.cpp:255 Cannot call method InfoRequest proxy /com/canonical/unity/lens/music does not exist WARN 2012-02-19 21:23:32 unity.glib.dbusproxy GLibDBusProxy.cpp:255 Cannot call method SetActive proxy /com/canonical/unity/lens/music does not exist WARN 2012-02-19 21:23:33 unity.iconloader IconLoader.cpp:509 Unable to load contents of file:///usr/share/icons/unity-icon-theme/places/svg/category-available.svg: Blad podczas otwierania pliku: Nie ma takiego pliku ani katalogu WARN 2012-02-19 21:23:33 unity.iconloader IconLoader.cpp:509 Unable to load contents of file:///usr/share/icons/unity-icon-theme/places/svg/category-installed.svg: Blad podczas otwierania pliku: Nie ma takiego pliku ani katalogu

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Building a better mouse-trap – Improving the creation of XML Message Requests using Reflection, XML & XSLT

- by paulschapman

Introduction The way I previously created messages to send to the GovTalk service I used the XMLDocument to create the request. While this worked it left a number of problems; not least that for every message a special function would need to created. This is OK for the short term but the biggest cost in any software project is maintenance and this would be a headache to maintain. So the following is a somewhat better way of achieving the same thing. For the purposes of this article I am going to be using the CompanyNumberSearch request of the GovTalk service – although this technique would work for any service that accepted XML. The C# functions which send and receive the messages remain the same. The magic sauce in this is the XSLT which defines the structure of the request, and the use of objects in conjunction with reflection to provide the content. It is a bit like Sweet Chilli Sauce added to Chicken on a bed of rice. So on to the Sweet Chilli Sauce The Sweet Chilli Sauce The request to search for a company based on it’s number is as follows; <GovTalkMessage xsi:schemaLocation="http://www.govtalk.gov.uk/CM/envelope http://xmlgw.companieshouse.gov.uk/v1-0/schema/Egov_ch-v2-0.xsd" xmlns="http://www.govtalk.gov.uk/CM/envelope" xmlns:dsig="http://www.w3.org/2000/09/xmldsig#" xmlns:gt="http://www.govtalk.gov.uk/schemas/govtalk/core" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" > <EnvelopeVersion>1.0</EnvelopeVersion> <Header> <MessageDetails> <Class>NumberSearch</Class> <Qualifier>request</Qualifier> <TransactionID>1</TransactionID> </MessageDetails> <SenderDetails> <IDAuthentication> <SenderID>????????????????????????????????</SenderID> <Authentication> <Method>CHMD5</Method> <Value>????????????????????????????????</Value> </Authentication> </IDAuthentication> </SenderDetails> </Header> <GovTalkDetails> <Keys/> </GovTalkDetails> <Body> <NumberSearchRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://xmlgw.companieshouse.gov.uk/v1-0/schema/NumberSearch.xsd"> <PartialCompanyNumber>99999999</PartialCompanyNumber> <DataSet>LIVE</DataSet> <SearchRows>1</SearchRows> </NumberSearchRequest> </Body> </GovTalkMessage> This is the XML that we send to the GovTalk Service and we get back a list of companies that match the criteria passed A message is structured in two parts; The envelope which identifies the person sending the request, with the name of the request, and the body which gives the detail of the company we are looking for. The Chilli What makes it possible is the use of XSLT to define the message – and serialization to convert each request object into XML. To start we need to create an object which will represent the contents of the message we are sending. However there is a common properties in all the messages that we send to Companies House. These properties are as follows SenderId – the id of the person sending the message SenderPassword – the password associated with Id TransactionId – Unique identifier for the message AuthenticationValue – authenticates the request Because these properties are unique to the Companies House message, and because they are shared with all messages they are perfect candidates for a base class. The class is as follows; using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Security.Cryptography; using System.Text; using System.Text.RegularExpressions; using Microsoft.WindowsAzure.ServiceRuntime; namespace CompanyHub.Services { public class GovTalkRequest { public GovTalkRequest() { try { SenderID = RoleEnvironment.GetConfigurationSettingValue("SenderId"); SenderPassword = RoleEnvironment.GetConfigurationSettingValue("SenderPassword"); TransactionId = DateTime.Now.Ticks.ToString(); AuthenticationValue = EncodePassword(String.Format("{0}{1}{2}", SenderID, SenderPassword, TransactionId)); } catch (System.Exception ex) { throw ex; } } /// <summary> /// returns the Sender ID to be used when communicating with the GovTalk Service /// </summary> public String SenderID { get; set; } /// <summary> /// return the password to be used when communicating with the GovTalk Service /// </summary> public String SenderPassword { get; set; } // end SenderPassword /// <summary> /// Transaction Id - uses the Time and Date converted to Ticks /// </summary> public String TransactionId { get; set; } // end TransactionId /// <summary> /// calculate the authentication value that will be used when /// communicating with /// </summary> public String AuthenticationValue { get; set; } // end AuthenticationValue property /// <summary> /// encodes password(s) using MD5 /// </summary> /// <param name="clearPassword"></param> /// <returns></returns> public static String EncodePassword(String clearPassword) { MD5CryptoServiceProvider md5Hasher = new MD5CryptoServiceProvider(); byte[] hashedBytes; UTF32Encoding encoder = new UTF32Encoding(); hashedBytes = md5Hasher.ComputeHash(ASCIIEncoding.Default.GetBytes(clearPassword)); String result = Regex.Replace(BitConverter.ToString(hashedBytes), "-", "").ToLower(); return result; } } } There is nothing particularly clever here, except for the EncodePassword method which hashes the value made up of the SenderId, Password and Transaction id. Each message inherits from this object. So for the Company Number Search in addition to the properties above we need a partial number, which dataset to search – for the purposes of the project we only need to search the LIVE set so this can be set in the constructor and the SearchRows. Again all are set as properties. With the SearchRows and DataSet initialized in the constructor. public class CompanyNumberSearchRequest : GovTalkRequest, IDisposable { /// <summary> /// /// </summary> public CompanyNumberSearchRequest() : base() { DataSet = "LIVE"; SearchRows = 1; } /// <summary> /// Company Number to search against /// </summary> public String PartialCompanyNumber { get; set; } /// <summary> /// What DataSet should be searched for the company /// </summary> public String DataSet { get; set; } /// <summary> /// How many rows should be returned /// </summary> public int SearchRows { get; set; } public void Dispose() { DataSet = String.Empty; PartialCompanyNumber = String.Empty; DataSet = "LIVE"; SearchRows = 1; } } As well as inheriting from our base class, I have also inherited from IDisposable – not just because it is just plain good practice to dispose of objects when coding, but it gives also gives us more versatility when using the object. There are four stages in making a request and this is reflected in the four methods we execute in making a call to the Companies House service; Create a request Send a request Check the status If OK then get the results of the request I’ve implemented each of these stages within a static class called Toolbox – which also means I don’t need to create an instance of the class to use it. When making a request there are three stages; Get the template for the message Serialize the object representing the message Transform the serialized object using a predefined XSLT file. Each of my templates I have defined as an embedded resource. When retrieving a resource of this kind we have to include the full namespace to the resource. In making the code re-usable as much as possible I defined the full ‘path’ within the GetRequest method. requestFile = String.Format("CompanyHub.Services.Schemas.{0}", RequestFile); So we now have the full path of the file within the assembly. Now all we need do is retrieve the assembly and get the resource. asm = Assembly.GetExecutingAssembly(); sr = asm.GetManifestResourceStream(requestFile); Once retrieved So this can be returned to the calling function and we now have a stream of XSLT to define the message. Time now to serialize the request to create the other side of this message. // Serialize object containing Request, Load into XML Document t = Obj.GetType(); ms = new MemoryStream(); serializer = new XmlSerializer(t); xmlTextWriter = new XmlTextWriter(ms, Encoding.ASCII); serializer.Serialize(xmlTextWriter, Obj); ms = (MemoryStream)xmlTextWriter.BaseStream; GovTalkRequest = Toolbox.ConvertByteArrayToString(ms.ToArray()); First off we need the type of the object so we make a call to the GetType method of the object containing the Message properties. Next we need a MemoryStream, XmlSerializer and an XMLTextWriter so these can be initialized. The object is serialized by making the call to the Serialize method of the serializer object. The result of that is then converted into a MemoryStream. That MemoryStream is then converted into a string. ConvertByteArrayToString This is a fairly simple function which uses an ASCIIEncoding object found within the System.Text namespace to convert an array of bytes into a string. public static String ConvertByteArrayToString(byte[] bytes) { System.Text.ASCIIEncoding enc = new System.Text.ASCIIEncoding(); return enc.GetString(bytes); } I only put it into a function because I will be using this in various places. The Sauce When adding support for other messages outside of creating a new object to store the properties of the message, the C# components do not need to change. It is in the XSLT file that the versatility of the technique lies. The XSLT file determines the format of the message. For the CompanyNumberSearch the XSLT file is as follows; <?xml version="1.0"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:template match="/"> <GovTalkMessage xsi:schemaLocation="http://www.govtalk.gov.uk/CM/envelope http://xmlgw.companieshouse.gov.uk/v1-0/schema/Egov_ch-v2-0.xsd" xmlns="http://www.govtalk.gov.uk/CM/envelope" xmlns:dsig="http://www.w3.org/2000/09/xmldsig#" xmlns:gt="http://www.govtalk.gov.uk/schemas/govtalk/core" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" > <EnvelopeVersion>1.0</EnvelopeVersion> <Header> <MessageDetails> <Class>NumberSearch</Class> <Qualifier>request</Qualifier> <TransactionID> <xsl:value-of select="CompanyNumberSearchRequest/TransactionId"/> </TransactionID> </MessageDetails> <SenderDetails> <IDAuthentication> <SenderID><xsl:value-of select="CompanyNumberSearchRequest/SenderID"/></SenderID> <Authentication> <Method>CHMD5</Method> <Value> <xsl:value-of select="CompanyNumberSearchRequest/AuthenticationValue"/> </Value> </Authentication> </IDAuthentication> </SenderDetails> </Header> <GovTalkDetails> <Keys/> </GovTalkDetails> <Body> <NumberSearchRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://xmlgw.companieshouse.gov.uk/v1-0/schema/NumberSearch.xsd"> <PartialCompanyNumber> <xsl:value-of select="CompanyNumberSearchRequest/PartialCompanyNumber"/> </PartialCompanyNumber> <DataSet> <xsl:value-of select="CompanyNumberSearchRequest/DataSet"/> </DataSet> <SearchRows> <xsl:value-of select="CompanyNumberSearchRequest/SearchRows"/> </SearchRows> </NumberSearchRequest> </Body> </GovTalkMessage> </xsl:template> </xsl:stylesheet> The outer two tags define that this is a XSLT stylesheet and the root tag from which the nodes are searched for. The GovTalkMessage is the format of the message that will be sent to Companies House. We first set up the XslCompiledTransform object which will transform the XSLT template and the serialized object into the request to Companies House. xslt = new XslCompiledTransform(); resultStream = new MemoryStream(); writer = new XmlTextWriter(resultStream, Encoding.ASCII); doc = new XmlDocument(); The Serialize method require XmlTextWriter to write the XML (writer) and a stream to place the transferred object into (writer). The XML will be loaded into an XMLDocument object (doc) prior to the transformation. // create XSLT Template xslTemplate = Toolbox.GetRequest(Template); xslTemplate.Seek(0, SeekOrigin.Begin); templateReader = XmlReader.Create(xslTemplate); xslt.Load(templateReader); I have stored all the templates as a series of Embedded Resources and the GetRequestCall takes the name of the template and extracts the relevent XSLT file. /// <summary> /// Gets the framwork XML which makes the request /// </summary> /// <param name="RequestFile"></param> /// <returns></returns> public static Stream GetRequest(String RequestFile) { String requestFile = String.Empty; Stream sr = null; Assembly asm = null; try { requestFile = String.Format("CompanyHub.Services.Schemas.{0}", RequestFile); asm = Assembly.GetExecutingAssembly(); sr = asm.GetManifestResourceStream(requestFile); } catch (Exception) { throw; } finally { asm = null; } return sr; } // end private static stream GetRequest We first take the template name and expand it to include the full namespace to the Embedded Resource I like to keep all my schemas in the same directory and so the namespace reflects this. The rest is the default namespace for the project. Then we get the currently executing assembly (which will contain the resources with the call to GetExecutingAssembly() ) Finally we get a stream which contains the XSLT file. We use this stream and then load an XmlReader with the contents of the template, and that is in turn loaded into the XslCompiledTransform object. We convert the object containing the message properties into Xml by serializing it; calling the Serialize() method of the XmlSerializer object. To set up the object we do the following; t = Obj.GetType(); ms = new MemoryStream(); serializer = new XmlSerializer(t); xmlTextWriter = new XmlTextWriter(ms, Encoding.ASCII); We first determine the type of the object being transferred by calling GetType() We create an XmlSerializer object by passing the type of the object being serialized. The serializer writes to a memory stream and that is linked to an XmlTextWriter. Next job is to serialize the object and load it into an XmlDocument. serializer.Serialize(xmlTextWriter, Obj); ms = (MemoryStream)xmlTextWriter.BaseStream; xmlRequest = new XmlTextReader(ms); GovTalkRequest = Toolbox.ConvertByteArrayToString(ms.ToArray()); doc.LoadXml(GovTalkRequest); Time to transform the XML to construct the full request. xslt.Transform(doc, writer); resultStream.Seek(0, SeekOrigin.Begin); request = Toolbox.ConvertByteArrayToString(resultStream.ToArray()); So that creates the full request to be sent to Companies House. Sending the request So far we have a string with a request for the Companies House service. Now we need to send the request to the Companies House Service. Configuration within an Azure project There are entire blog entries written about configuration within an Azure project – most of this is out of scope for this article but the following is a summary. Configuration is defined in two files within the parent project *.csdef which contains the definition of configuration setting. <?xml version="1.0" encoding="utf-8"?> <ServiceDefinition name="OnlineCompanyHub" xmlns="http://schemas.microsoft.com/ServiceHosting/2008/10/ServiceDefinition"> <WebRole name="CompanyHub.Host"> <InputEndpoints> <InputEndpoint name="HttpIn" protocol="http" port="80" /> </InputEndpoints> <ConfigurationSettings> <Setting name="DiagnosticsConnectionString" /> <Setting name="DataConnectionString" /> </ConfigurationSettings> </WebRole> <WebRole name="CompanyHub.Services"> <InputEndpoints> <InputEndpoint name="HttpIn" protocol="http" port="8080" /> </InputEndpoints> <ConfigurationSettings> <Setting name="DiagnosticsConnectionString" /> <Setting name="SenderId"/> <Setting name="SenderPassword" /> <Setting name="GovTalkUrl"/> </ConfigurationSettings> </WebRole> <WorkerRole name="CompanyHub.Worker"> <ConfigurationSettings> <Setting name="DiagnosticsConnectionString" /> </ConfigurationSettings> </WorkerRole> </ServiceDefinition> Above is the configuration definition from the project. What we are interested in however is the ConfigurationSettings tag of the CompanyHub.Services WebRole. There are four configuration settings here, but at the moment we are interested in the second to forth settings; SenderId, SenderPassword and GovTalkUrl The value of these settings are defined in the ServiceDefinition.cscfg file; <?xml version="1.0"?> <ServiceConfiguration serviceName="OnlineCompanyHub" xmlns="http://schemas.microsoft.com/ServiceHosting/2008/10/ServiceConfiguration"> <Role name="CompanyHub.Host"> <Instances count="2" /> <ConfigurationSettings> <Setting name="DiagnosticsConnectionString" value="UseDevelopmentStorage=true" /> <Setting name="DataConnectionString" value="UseDevelopmentStorage=true" /> </ConfigurationSettings> </Role> <Role name="CompanyHub.Services"> <Instances count="2" /> <ConfigurationSettings> <Setting name="DiagnosticsConnectionString" value="UseDevelopmentStorage=true" /> <Setting name="SenderId" value="UserID"/> <Setting name="SenderPassword" value="Password"/> <Setting name="GovTalkUrl" value="http://xmlgw.companieshouse.gov.uk/v1-0/xmlgw/Gateway"/> </ConfigurationSettings> </Role> <Role name="CompanyHub.Worker"> <Instances count="2" /> <ConfigurationSettings> <Setting name="DiagnosticsConnectionString" value="UseDevelopmentStorage=true" /> </ConfigurationSettings> </Role> </ServiceConfiguration> Look for the Role tag that contains our project name (CompanyHub.Services). Having configured the parameters we can now transmit the request. This is done by ‘POST’ing a stream of XML to the Companies House servers. govTalkUrl = RoleEnvironment.GetConfigurationSettingValue("GovTalkUrl"); request = WebRequest.Create(govTalkUrl); request.Method = "POST"; request.ContentType = "text/xml"; writer = new StreamWriter(request.GetRequestStream()); writer.WriteLine(RequestMessage); writer.Close(); We use the WebRequest object to send the object. Set the method of sending to ‘POST’ and the type of data as text/xml. Once set up all we do is write the request to the writer – this sends the request to Companies House. Did the Request Work Part I – Getting the response Having sent a request – we now need the result of that request. response = request.GetResponse(); reader = response.GetResponseStream(); result = Toolbox.ConvertByteArrayToString(Toolbox.ReadFully(reader)); The WebRequest object has a GetResponse() method which allows us to get the response sent back. Like many of these calls the results come in the form of a stream which we convert into a string. Did the Request Work Part II – Translating the Response Much like XSLT and XML were used to create the original request, so it can be used to extract the response and by deserializing the result we create an object that contains the response. Did it work? It would be really great if everything worked all the time. Of course if it did then I don’t suppose people would pay me and others the big bucks so that our programmes do not a) Collapse in a heap (this is an area of memory) b) Blow every fuse in the place in a shower of sparks (this will probably not happen this being real life and not a Hollywood movie, but it was possible to blow the sound system of a BBC Model B with a poorly coded setting) c) Go nuts and trap everyone outside the airlock (this was from a movie, and unless NASA get a manned moon/mars mission set up unlikely to happen) d) Go nuts and take over the world (this was also from a movie, but please note life has a habit of being of exceeding the wildest imaginations of Hollywood writers (note writers – Hollywood executives have no imagination and judging by recent output of that town have turned plagiarism into an art form). e) Freeze in total confusion because the cleaner pulled the plug to the internet router (this has happened) So anyway – we need to check to see if our request actually worked. Within the GovTalk response there is a section that details the status of the message and a description of what went wrong (if anything did). I have defined an XSLT template which will extract these into an XML document. <?xml version="1.0"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:ev="http://www.govtalk.gov.uk/CM/envelope" xmlns:gt="http://www.govtalk.gov.uk/schemas/govtalk/core" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <xsl:template match="/"> <GovTalkStatus xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Status> <xsl:value-of select="ev:GovTalkMessage/ev:Header/ev:MessageDetails/ev:Qualifier"/> </Status> <Text> <xsl:value-of select="ev:GovTalkMessage/ev:GovTalkDetails/ev:GovTalkErrors/ev:Error/ev:Text"/> </Text> <Location> <xsl:value-of select="ev:GovTalkMessage/ev:GovTalkDetails/ev:GovTalkErrors/ev:Error/ev:Location"/> </Location> <Number> <xsl:value-of select="ev:GovTalkMessage/ev:GovTalkDetails/ev:GovTalkErrors/ev:Error/ev:Number"/> </Number> <Type> <xsl:value-of select="ev:GovTalkMessage/ev:GovTalkDetails/ev:GovTalkErrors/ev:Error/ev:Type"/> </Type> </GovTalkStatus> </xsl:template> </xsl:stylesheet> Only thing different about previous XSL files is the references to two namespaces ev & gt. These are defined in the GovTalk response at the top of the response; xsi:schemaLocation="http://www.govtalk.gov.uk/CM/envelope http://xmlgw.companieshouse.gov.uk/v1-0/schema/Egov_ch-v2-0.xsd" xmlns="http://www.govtalk.gov.uk/CM/envelope" xmlns:dsig="http://www.w3.org/2000/09/xmldsig#" xmlns:gt="http://www.govtalk.gov.uk/schemas/govtalk/core" If we do not put these references into the XSLT template then the XslCompiledTransform object will not be able to find the relevant tags. Deserialization is a fairly simple activity. encoder = new ASCIIEncoding(); ms = new MemoryStream(encoder.GetBytes(statusXML)); serializer = new XmlSerializer(typeof(GovTalkStatus)); xmlTextWriter = new XmlTextWriter(ms, Encoding.ASCII); messageStatus = (GovTalkStatus)serializer.Deserialize(ms); We set up a serialization object using the object type containing the error state and pass to it the results of a transformation between the XSLT above and the GovTalk response. Now we have an object containing any error state, and the error message. All we need to do is check the status. If there is an error then we can flag an error. If not then we extract the results and pass that as an object back to the calling function. We go this by guess what – defining an XSLT template for the result and using that to create an Xml Stream which can be deserialized into a .Net object. In this instance the XSLT to create the result of a Company Number Search is; <?xml version="1.0" encoding="us-ascii"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:ev="http://www.govtalk.gov.uk/CM/envelope" xmlns:sch="http://xmlgw.companieshouse.gov.uk/v1-0/schema" exclude-result-prefixes="ev"> <xsl:template match="/"> <CompanySearchResult xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <CompanyNumber> <xsl:value-of select="ev:GovTalkMessage/ev:Body/sch:NumberSearch/sch:CoSearchItem/sch:CompanyNumber"/> </CompanyNumber> <CompanyName> <xsl:value-of select="ev:GovTalkMessage/ev:Body/sch:NumberSearch/sch:CoSearchItem/sch:CompanyName"/> </CompanyName> </CompanySearchResult> </xsl:template> </xsl:stylesheet> and the object definition is; using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace CompanyHub.Services { public class CompanySearchResult { public CompanySearchResult() { CompanyNumber = String.Empty; CompanyName = String.Empty; } public String CompanyNumber { get; set; } public String CompanyName { get; set; } } } Our entire code to make calls to send a request, and interpret the results are; String request = String.Empty; String response = String.Empty; GovTalkStatus status = null; fault = null; try { using (CompanyNumberSearchRequest requestObj = new CompanyNumberSearchRequest()) { requestObj.PartialCompanyNumber = CompanyNumber; request = Toolbox.CreateRequest(requestObj, "CompanyNumberSearch.xsl"); response = Toolbox.SendGovTalkRequest(request); status = Toolbox.GetMessageStatus(response); if (status.Status.ToLower() == "error") { fault = new HubFault() { Message = status.Text }; } else { Object obj = Toolbox.GetGovTalkResponse(response, "CompanyNumberSearchResult.xsl", typeof(CompanySearchResult)); } } } catch (FaultException<ArgumentException> ex) { fault = new HubFault() { FaultType = ex.Detail.GetType().FullName, Message = ex.Detail.Message }; } catch (System.Exception ex) { fault = new HubFault() { FaultType = ex.GetType().FullName, Message = ex.Message }; } finally { } Wrap up So there we have it – a reusable set of functions to send and interpret XML results from an internet based service. The code is reusable with a little change with any service which uses XML as a transport mechanism – and as for the Companies House GovTalk service all I need to do is create various objects for the result and message sent and the relevent XSLT files. I might need minor changes for other services but something like 70-90% will be exactly the same.

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Code Contracts: validating arrays and collections

- by DigiMortal

Validating collections before using them is very common task when we use built-in generic types for our collections. In this posting I will show you how to validate collections using code contracts. It is cool how much awful looking code you can avoid using code contracts. Failing code Let’s suppose we have method that calculates sum of all invoices in collection. We have class Invoice and one of properties it has is Sum. I don’t introduce here any complex calculations on invoices because we have another problem to solve in this topic. Here is our code. public static decimal CalculateTotal(IList<Invoice> invoices) { var sum = invoices.Sum(p => p.Sum); return sum; } This method is very simple but it fails when invoices list contains at least one null. Of course, we can test if invoice is null but having nulls in lists like this is not good idea – it opens green way for different coding bugs in system. Our goal is to react to bugs ASAP at the nearest place they occur. There is one more way how to make our method fail. It happens when invoices is null. I thing it is also one common bugs during development and it even happens in production environments under some conditions that are usually hardly met. Now let’s protect our little calculation method with code contracts. We need two contracts: invoices cannot be null invoices cannot contain any nulls Our first contract is easy but how to write the second one? Solution: Contract.ForAll Preconditions in code are checked using Contract.Ensures method. This method takes boolean value as argument that sais if contract holds or not. There is also method Contract.ForAll that takes collection and predicate that must hold for that collection. Nice thing is ForAll returns boolean. So, we have very simple solution. public static decimal CalculateTotal(IList<Invoice> invoices) { Contract.Requires(invoices != null); Contract.Requires(Contract.ForAll<Invoice>(invoices, p => p != null)); var sum = invoices.Sum(p => p.Sum); return sum; } And here are some lines of code you can use to test the contracts quickly. var invoices = new List<Invoice>(); invoices.Add(new Invoice()); invoices.Add(null); invoices.Add(new Invoice()); //CalculateTotal(null); CalculateTotal(invoices); If your code is covered with unit tests then I suggest you to write tests to check that these contracts hold for every code run. Conclusion Although it seemed at first place that checking all elements in collection may end up with for-loops that does not look so nice we were able to solve our problem nicely. ForAll method of contract class offered us simple mechanism to check collections and it does it smoothly the code-contracts-way. P.S. I suggest you also read devlicio.us blog posting Validating Collections with Code Contracts by Derik Whittaker.

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Why you shouldn't add methods to interfaces in APIs

- by Simon Cooper

It is an oft-repeated maxim that you shouldn't add methods to a publically-released interface in an API. Recently, I was hit hard when this wasn't followed. As part of the work on ApplicationMetrics, I've been implementing auto-reporting of MVC action methods; whenever an action was called on a controller, ApplicationMetrics would automatically report it without the developer needing to add manual ReportEvent calls. Fortunately, MVC provides easy hook when a controller is created, letting me log when it happens - the IControllerFactory interface. Now, the dll we provide to instrument an MVC webapp has to be compiled against .NET 3.5 and MVC 1, as the lowest common denominator. This MVC 1 dll will still work when used in an MVC 2, 3 or 4 webapp because all MVC 2+ webapps have a binding redirect redirecting all references to previous versions of System.Web.Mvc to the correct version, and type forwards taking care of any moved types in the new assemblies. Or at least, it should. IControllerFactory In MVC 1 and 2, IControllerFactory was defined as follows: public interface IControllerFactory { IController CreateController(RequestContext requestContext, string controllerName); void ReleaseController(IController controller); } So, to implement the logging controller factory, we simply wrap the existing controller factory: internal sealed class LoggingControllerFactory : IControllerFactory { private readonly IControllerFactory m_CurrentController; public LoggingControllerFactory(IControllerFactory currentController) { m_CurrentController = currentController; } public IController CreateController( RequestContext requestContext, string controllerName) { // log the controller being used FeatureSessionData.ReportEvent("Controller used:", controllerName); return m_CurrentController.CreateController(requestContext, controllerName); } public void ReleaseController(IController controller) { m_CurrentController.ReleaseController(controller); } } Easy. This works as expected in MVC 1 and 2. However, in MVC 3 this type was throwing a TypeLoadException, saying a method wasn't implemented. It turns out that, in MVC 3, the definition of IControllerFactory was changed to this: public interface IControllerFactory { IController CreateController(RequestContext requestContext, string controllerName); SessionStateBehavior GetControllerSessionBehavior( RequestContext requestContext, string controllerName); void ReleaseController(IController controller); } There's a new method in the interface. So when our MVC 1 dll was redirected to reference System.Web.Mvc v3, LoggingControllerFactory tried to implement version 3 of IControllerFactory, was missing the GetControllerSessionBehaviour method, and so couldn't be loaded by the CLR. Implementing the new method Fortunately, there was a workaround. Because interface methods are normally implemented implicitly in the CLR, if we simply declare a virtual method matching the signature of the new method in MVC 3, then it will be ignored in MVC 1 and 2 and implement the extra method in MVC 3: internal sealed class LoggingControllerFactory : IControllerFactory { ... public virtual SessionStateBehaviour GetControllerSessionBehaviour( RequestContext requestContext, string controllerName) {} ... } However, this also has problems - the SessionStateBehaviour type only exists in .NET 4, and we're limited to .NET 3.5 by support for MVC 1 and 2. This means that the only solutions to support all MVC versions are: Construct the LoggingControllerFactory type at runtime using reflection Produce entirely separate dlls for MVC 1&2 and MVC 3. Ugh. And all because of that blasted extra method! Another solution? Fortunately, in this case, there is a third option - System.Web.Mvc also provides a DefaultControllerFactory type that can provide the implementation of GetControllerSessionBehaviour for us in MVC 3, while still allowing us to override CreateController and ReleaseController. However, this does mean that LoggingControllerFactory won't be able to wrap any calls to GetControllerSessionBehaviour. This is an acceptable bug, given the other options, as very few developers will be overriding GetControllerSessionBehaviour in their own custom controller factory. So, if you're providing an interface as part of an API, then please please please don't add methods to it. Especially if you don't provide a 'default' implementing type. Any code compiled against the previous version that can't be updated will have some very tough decisions to make to support both versions.

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C#, Delegates and LINQ

- by JustinGreenwood

One of the topics many junior programmers struggle with is delegates. And today, anonymous delegates and lambda expressions are profuse in .net APIs. To help some VB programmers adapt to C# and the many equivalent flavors of delegates, I walked through some simple samples to show them the different flavors of delegates. using System; using System.Collections.Generic; using System.Linq; namespace DelegateExample { class Program { public delegate string ProcessStringDelegate(string data); public static string ReverseStringStaticMethod(string data) { return new String(data.Reverse().ToArray()); } static void Main(string[] args) { var stringDelegates = new List<ProcessStringDelegate> { //========================================================== // Declare a new delegate instance and pass the name of the method in new ProcessStringDelegate(ReverseStringStaticMethod), //========================================================== // A shortcut is to just and pass the name of the method in ReverseStringStaticMethod, //========================================================== // You can create an anonymous delegate also delegate (string inputString) //Scramble { var outString = inputString; if (!string.IsNullOrWhiteSpace(inputString)) { var rand = new Random(); var chs = inputString.ToCharArray(); for (int i = 0; i < inputString.Length * 3; i++) { int x = rand.Next(chs.Length), y = rand.Next(chs.Length); char c = chs[x]; chs[x] = chs[y]; chs[y] = c; } outString = new string(chs); } return outString; }, //========================================================== // yet another syntax would be the lambda expression syntax inputString => { // ROT13 var array = inputString.ToCharArray(); for (int i = 0; i < array.Length; i++) { int n = (int)array[i]; n += (n >= 'a' && n <= 'z') ? ((n > 'm') ? 13 : -13) : ((n >= 'A' && n <= 'Z') ? ((n > 'M') ? 13 : -13) : 0); array[i] = (char)n; } return new string(array); } //========================================================== }; // Display the results of the delegate calls var stringToTransform = "Welcome to the jungle!"; System.Console.ForegroundColor = ConsoleColor.Cyan; System.Console.Write("String to Process: "); System.Console.ForegroundColor = ConsoleColor.Yellow; System.Console.WriteLine(stringToTransform); stringDelegates.ForEach(delegatePointer => { System.Console.WriteLine(); System.Console.ForegroundColor = ConsoleColor.Cyan; System.Console.Write("Delegate Method Name: "); System.Console.ForegroundColor = ConsoleColor.Magenta; System.Console.WriteLine(delegatePointer.Method.Name); System.Console.ForegroundColor = ConsoleColor.Cyan; System.Console.Write("Delegate Result: "); System.Console.ForegroundColor = ConsoleColor.White; System.Console.WriteLine(delegatePointer(stringToTransform)); }); System.Console.ReadKey(); } } } The output of the program is below: String to Process: Welcome to the jungle! Delegate Method Name: ReverseStringStaticMethod Delegate Result: !elgnuj eht ot emocleW Delegate Method Name: ReverseStringStaticMethod Delegate Result: !elgnuj eht ot emocleW Delegate Method Name: b__1 Delegate Result: cg ljotWotem!le une eh Delegate Method Name: b__2 Delegate Result: dX_V|`X ?| ?[X ]?{Z_X!

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C# 5 Async, Part 3: Preparing Existing code For Await

- by Reed

While the Visual Studio Async CTP provides a fantastic model for asynchronous programming, it requires code to be implemented in terms of Task and Task<T>. The CTP adds support for Task-based asynchrony to the .NET Framework methods, and promises to have these implemented directly in the framework in the future. However, existing code outside the framework will need to be converted to using the Task class prior to being usable via the CTP. Wrapping existing asynchronous code into a Task or Task<T> is, thankfully, fairly straightforward. There are two main approaches to this. Code written using the Asynchronous Programming Model (APM) is very easy to convert to using Task<T>. The TaskFactory class provides the tools to directly convert APM code into a method returning a Task<T>. This is done via the FromAsync method. This method takes the BeginOperation and EndOperation methods, as well as any parameters and state objects as arguments, and returns a Task<T> directly. For example, we could easily convert the WebRequest BeginGetResponse and EndGetResponse methods into a method which returns a Task<WebResponse> via: Task<WebResponse> task = Task.Factory .FromAsync<WebResponse>( request.BeginGetResponse, request.EndGetResponse, null); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Event-based Asynchronous Pattern (EAP) code can also be wrapped into a Task<T>, though this requires a bit more effort than the one line of code above. This is handled via the TaskCompletionSource<T> class. MSDN provides a detailed example of using this to wrap an EAP operation into a method returning Task<T>. It demonstrates handling cancellation and exception handling as well as the basic operation of the asynchronous method itself. The basic form of this operation is typically: Task<YourResult> GetResultAsync() { var tcs = new TaskCompletionSource<YourResult>(); // Handle the event, and setup the task results... this.GetResultCompleted += (o,e) => { if (e.Error != null) tcs.TrySetException(e.Error); else if (e.Cancelled) tcs.TrySetCanceled(); else tcs.TrySetResult(e.Result); }; // Call the asynchronous method this.GetResult(); // Return the task from the TaskCompletionSource return tcs.Task; } We can easily use these methods to wrap our own code into a method that returns a Task<T>. Existing libraries which cannot be edited can be extended via Extension methods. The CTP uses this technique to add appropriate methods throughout the framework. The suggested naming for these methods is to define these methods as “Task<YourResult> YourClass.YourOperationAsync(…)”. However, this naming often conflicts with the default naming of the EAP. If this is the case, the CTP has standardized on using “Task<YourResult> YourClass.YourOperationTaskAsync(…)”. Once we’ve wrapped all of our existing code into operations that return Task<T>, we can begin investigating how the Async CTP can be used with our own code.

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Javascript Inheritance Part 2

- by PhubarBaz

A while back I wrote about Javascript inheritance, trying to figure out the best and easiest way to do it (http://geekswithblogs.net/PhubarBaz/archive/2010/07/08/javascript-inheritance.aspx). That was 2 years ago and I've learned a lot since then. But only recently have I decided to just leave classical inheritance behind and embrace prototypal inheritance. For most of us, we were trained in classical inheritance, using class hierarchies in a typed language. Unfortunately Javascript doesn't follow that model. It is both classless and typeless, which is hard to fathom for someone who's been using classes the last 20 years. For the last two or three years since I've got into Javascript I've been trying to find the best way to force it into the class model without much success. It's clunky and verbose and hard to understand. I think my biggest problem was that it felt so wrong to add or change object members at run time. Every time I did it I felt like I needed a shower. That's the 20 years of classical inheritance in me. Finally I decided to embrace change and do something different. I decided to use the factory pattern to build objects instead of trying to use inheritance. Javascript was made for the factory pattern because of the way you can construct objects at runtime. In the factory pattern you have a factory function that you call and tell it to give you a certain type of object back. The factory function takes care of constructing the object to your specification. Here's an example. Say we want to have some shape objects and they have common attributes like id and area that we want to depend on in other parts of your application. So first thing to do is create a factory object and give it a factory method to create an abstract shape object. The factory method builds the object then returns it. var shapeFactory = { getShape: function(id){ var shape = { id: id, area: function() { throw "Not implemented"; } }; return shape; }}; Now we can add another factory method to get a rectangle. It calls the getShape() method first and then adds an implementation to it. getRectangle: function(id, width, height){ var rect = this.getShape(id); rect.width = width; rect.height = height; rect.area = function() { return this.width * this.height; }; return rect;} That's pretty simple right? No worrying about hooking up prototypes and calling base constructors or any of that crap I used to do. Now let's create a factory method to get a cuboid (rectangular cube). The cuboid object will extend the rectangle object. To get the area we will call into the base object's area method and then multiply that by the depth. getCuboid: function(id, width, height, depth){ var cuboid = this.getRectangle(id, width, height); cuboid.depth = depth; var baseArea = cuboid.area; cuboid.area = function() { var a = baseArea.call(this); return a * this.depth; } return cuboid;} See how we called the area method in the base object? First we save it off in a variable then we implement our own area method and use call() to call the base function. For me this is a lot cleaner and easier than trying to emulate class hierarchies in Javascript.

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How can I automatically update Flash Player whenever a new version is released? [closed]

- by user219950

Summary: Flash Player Update Service doesn't run on a reliable schedule, and doesn't automatically download and apply updates when it does run. Given the importance of having an up-to-date version of Flash Player installed (for those of us who don't use Chrome with its built-in player), I would like to find a way to ensure that new updates are promptly detected and installed. What follows are the details of my efforts to solve this problem on my own... Appendix A: Flash Player Update Service OK, way back in Flash Player 11.2 (or so?) Adobe added the Flash Player Update Service (FlashPlayerUpdateService.exe), it was supposed to keep the Flash Player updated... Upon installation, FPUS is configured to run as a Windows Service, with Start Type set to Manual. A Scheduled Task (Adobe Flash Player Updater.job) is added to start this service every hour. So far, so good - this set-up avoids having a constantly-running service, but makes sure that the checks are run often enough to catch any updates quickly. Google's software updater is configured in a similar fashion, and that works just fine... ...And yet, when I checked the version of my installed Flash Player, I found it was 11.6.602.180, which, based on looking at the timestamps of the files in C:\Windows\System32\Macromed\Flash was last updated (or installed) on Tue, Mar 12, 2013 --- 3/12/13, 5:00:08pm. I made this observation on Thu, Apr 25, 2013 --- 4/25/13, 7:00:00pm, and upon checking Adobe's website found that the current version of Flash Player was 11.7.700.169. That's over a month since the last update, with a new one clearly available on the website but with no indication that the hourly check running on my machine has noticed it or has any intention of downloading it. Appendix B: running the Flash Player updater manually Once upon a time, running FlashUtil32_<version_Plugin.exe -update plugin would give you a window with an Install button; pressing it would download the installer for the current version (automatically, without opening a browser) and run it, then you'd click thru that installer & be done. It was manual, but it worked! Finding my current installation out of date (see Appendix A), I first tried this manual update process. However... Running FlashUtil32_<version_ActiveX.exe -update activex (in my case, that's FlashUtil32_11_6_602_180_ActiveX.exe -update activex) ...only presents a window with a Download button, clicking that Download button opens my browser to the URL https://get3.adobe.com/flashplayer/update/activex. Running FlashUtil32_<version_Plugin.exe -update plugin (in my case, that's FlashUtil32_11_6_602_180_Plugin.exe -update plugin) ...only presents a window with a Download button, clicking that Download button opens my browser to the URL https://get3.adobe.com/flashplayer/update/plugin. I could continue with the Download page it sent me to, uncheck the foistware box ("Free! McAfee Security Scan Plus"), download that installer (ActiveX, no foistware: install_flashplayer11x32axau_mssd_aih.exe, Plugin, no foistware: install_flashplayer11x32au_mssd_aih.exe) & probably have an updated Flash...but then, what is the point of the Flash Player Update Service if I have to manually download & run another exe? Epilogue I've since come to suspect that the update service is intentionally hobbled to drive early adopters to the manual download page. If this is true, there's probably no solution to this short of writing my own updater; hopefully I am wrong.

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Delaying NIS & NFS startup till after network interface is fully ready on Fedora 17

- by obmarg

I've recently set up a fedora 17 server for our network, and I've been having trouble getting the NIS service to work on startup. Here's some logs from the system: Aug 21 12:57:12 cairnwell ypbind-pre-setdomain[718]: Setting NIS domain: 'indigo-nis' (environment variable) Aug 21 12:57:13 cairnwell ypbind: Binding NIS service Aug 21 12:57:13 cairnwell rpc.statd[730]: Unable to prune capability 0 from bounding set: Operation not permitted Aug 21 12:57:13 cairnwell systemd[1]: nfs-lock.service: control process exited, code=exited status=1 Aug 21 12:57:13 cairnwell systemd[1]: Unit nfs-lock.service entered failed state. Aug 21 12:57:14 cairnwell setroubleshoot: SELinux is preventing /usr/sbin/rpc.statd from using the setpcap capability. For complete SELinux messages. run sealert -l 024bba8a-b0ef-43dc-b195-5c9a2d4c4d41 Aug 21 12:57:15 cairnwell kernel: [ 18.822282] bnx2 0000:02:00.0: em1: NIC Copper Link is Up, 1000 Mbps full duplex Aug 21 12:57:15 cairnwell kernel: [ 18.822925] ADDRCONF(NETDEV_CHANGE): em1: link becomes ready Aug 21 12:57:15 cairnwell NetworkManager[621]: <info> (em1): carrier now ON (device state 20) Aug 21 12:57:15 cairnwell NetworkManager[621]: <info> (em1): device state change: unavailable -> disconnected (reason 'carrier-changed') [20 30 40] Aug 21 12:57:15 cairnwell NetworkManager[621]: <info> Auto-activating connection 'System em1'. Aug 21 12:57:15 cairnwell NetworkManager[621]: <info> Activation (em1) starting connection 'System em1' Aug 21 12:57:15 cairnwell NetworkManager[621]: <info> (em1): device state change: disconnected -> prepare (reason 'none') [30 40 0] ....... Aug 21 12:57:19 cairnwell sendmail[790]: YPBINDPROC_DOMAIN: Domain not bound Aug 21 12:57:26 cairnwell sendmail[790]: YPBINDPROC_DOMAIN: Domain not bound Aug 21 12:57:31 cairnwell sendmail[790]: YPBINDPROC_DOMAIN: Domain not bound Aug 21 12:57:35 cairnwell sendmail[790]: YPBINDPROC_DOMAIN: Domain not bound Aug 21 12:58:00 cairnwell ypbind: Binding took 47 seconds Aug 21 12:58:00 cairnwell ypbind: NIS server for domain indigo-nis is not responding. Aug 21 12:58:01 cairnwell ypbind: Killing ypbind with PID 733. Aug 21 12:58:01 cairnwell ypbind-post-waitbind[734]: /usr/lib/ypbind/ypbind-post-waitbind: line 51: kill: SIGTERM: invalid signal specification Aug 21 12:58:01 cairnwell systemd[1]: ypbind.service: control process exited, code=exited status=1 Aug 21 12:58:01 cairnwell systemd[1]: Unit ypbind.service entered failed state. By the looks of these logs the ypbind service is starting up at 12:57:12 but the network interface isn't coming up till 12:57:15. My guess is that this is causing ypbind to time out when trying to connect. As a knock-on effect the NIS failure is causing problems with NFS which is no longer able to map UIDs properly. This problem doesn't seem to be fixed by actually starting ypbind etc. so I've had to set all my NFS shares to noauto. I have tried manually adding NETWORKDELAY and NETWORKWAIT in /etc/sysconfig/network and also running systemctl enable NetworkManager-wait-online.service as I've seen suggested in some places, but neither of these have had any effect. It is relatively easy to fix manually by restarting ypbind & mounting NFS shares after the network has started up, but it's less than ideal to have to do this every time the server has been rebooted. Does anyone know of an easy (and preferably hack-free) way of delaying the ypbind startup till after the network interface is fully ready?

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Centos 7. Freeradius fails to start on boot

- by Alex

I was messing around with FreeRADIUS and MySQL (MariaDB) and it seems FreeRADIUS service can't start properly on startup. But it starts fine using root user or in debug mode (radiusd -X) and works just fine! Debug mode shows no errors. systemctl command shows that radiusd.service has failed to start. /var/log/messages output: Aug 21 15:52:29 nexus-test systemd: Starting The Apache HTTP Server... Aug 21 15:52:29 nexus-test systemd: Starting MariaDB database server... Aug 21 15:52:29 nexus-test systemd: Starting FreeRADIUS high performance RADIUS server.... Aug 21 15:52:29 nexus-test systemd: Started OpenSSH server daemon. Aug 21 15:52:29 nexus-test mysqld_safe: 140821 15:52:29 mysqld_safe Logging to '/var/log/mariadb/mariadb.log'. Aug 21 15:52:29 nexus-test mysqld_safe: 140821 15:52:29 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql Aug 21 15:52:30 nexus-test systemd: Started Postfix Mail Transport Agent. Aug 21 15:52:30 nexus-test avahi-daemon[604]: Registering new address record for fe80::250:56ff:fe85:e4af on eth0.*. Aug 21 15:52:30 nexus-test systemd: radiusd.service: control process exited, code=exited status=1 Aug 21 15:52:30 nexus-test systemd: Failed to start FreeRADIUS high performance RADIUS server.. Aug 21 15:52:30 nexus-test systemd: Unit radiusd.service entered failed state. Aug 21 15:52:31 nexus-test kdumpctl: kexec: loaded kdump kernel Aug 21 15:52:31 nexus-test kdumpctl: Starting kdump: [OK] Aug 21 15:52:31 nexus-test systemd: Started Crash recovery kernel arming. Aug 21 15:52:31 nexus-test systemd: Started The Apache HTTP Server. Aug 21 15:52:31 nexus-test systemd: Started MariaDB database server. /var/log/radius/radius.log output: Thu Aug 21 15:24:16 2014 : Info: rlm_sql (sql): Driver rlm_sql_mysql (module rlm_sql_mysql) loaded and linked Thu Aug 21 15:24:16 2014 : Info: rlm_sql (sql): Attempting to connect to database "radius" Thu Aug 21 15:24:16 2014 : Info: rlm_sql (sql): Opening additional connection (0) Thu Aug 21 15:24:16 2014 : Error: rlm_sql_mysql: Couldn't connect socket to MySQL server radius@localhost:radius Thu Aug 21 15:24:16 2014 : Error: rlm_sql_mysql: Mysql error 'Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)' Thu Aug 21 15:24:16 2014 : Error: rlm_sql (sql): Opening connection failed (0) Thu Aug 21 15:24:16 2014 : Error: /etc/raddb/mods-enabled/sql[47]: Instantiation failed for module "sql" After seeing this I tried to replicate the problem, killed mariadb.service and started to run debug mode again. And it spits out the same problem as in the radius.log. I tried disabling iptables and firewalld and rebooting, but no luck: systemctl disable iptables systemctl disable firewalld So maybe the problem is in the process startup order or delay of some kind. Maybe FreeRADIUS's SQL module can't connect to not yet started MariaDB? If it, how can I fix this? In earlier versions of RHEL/CENTOS I know you easily see service start order in like rc.d or stuff, now IDK. I am new to this fancy "systemd", "systemctl", "firewalld" stuff Centos 7 introduced so sorry I'm a little bit confused. Also this new FreeRADIUS 3 structure... PS. MariaDB is enabled on startup, credentials in FR DB configuration are correct A little update: cat /etc/systemd/system/multi-user.target.wants/radiusd.service output: [Unit] Description=FreeRADIUS high performance RADIUS server. After=syslog.target network.target [Service] Type=forking PIDFile=/var/run/radiusd/radiusd.pid ExecStartPre=-/bin/chown -R radiusd.radiusd /var/run/radiusd ExecStartPre=/usr/sbin/radiusd -C ExecStart=/usr/sbin/radiusd -d /etc/raddb ExecReload=/usr/sbin/radiusd -C ExecReload=/bin/kill -HUP $MAINPID [Install] WantedBy=multi-user.target

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C# 5 Async, Part 1: Simplifying Asynchrony – That for which we await

- by Reed

Today’s announcement at PDC of the future directions C# is taking excite me greatly. The new Visual Studio Async CTP is amazing. Asynchronous code – code which frustrates and demoralizes even the most advanced of developers, is taking a huge leap forward in terms of usability. This is handled by building on the Task functionality in .NET 4, as well as the addition of two new keywords being added to the C# language: async and await. This core of the new asynchronous functionality is built upon three key features. First is the Task functionality in .NET 4, and based on Task and Task<TResult>. While Task was intended to be the primary means of asynchronous programming with .NET 4, the .NET Framework was still based mainly on the Asynchronous Pattern and the Event-based Asynchronous Pattern. The .NET Framework added functionality and guidance for wrapping existing APIs into a Task based API, but the framework itself didn’t really adopt Task or Task<TResult> in any meaningful way. The CTP shows that, going forward, this is changing. One of the three key new features coming in C# is actually a .NET Framework feature. Nearly every asynchronous API in the .NET Framework has been wrapped into a new, Task-based method calls. In the CTP, this is done via as external assembly (AsyncCtpLibrary.dll) which uses Extension Methods to wrap the existing APIs. However, going forward, this will be handled directly within the Framework. This will have a unifying effect throughout the .NET Framework. This is the first building block of the new features for asynchronous programming: Going forward, all asynchronous operations will work via a method that returns Task or Task<TResult> The second key feature is the new async contextual keyword being added to the language. The async keyword is used to declare an asynchronous function, which is a method that either returns void, a Task, or a Task<T>. Inside the asynchronous function, there must be at least one await expression. This is a new C# keyword (await) that is used to automatically take a series of statements and break it up to potentially use discontinuous evaluation. This is done by using await on any expression that evaluates to a Task or Task<T>. For example, suppose we want to download a webpage as a string. There is a new method added to WebClient: Task<string> WebClient.DownloadStringTaskAsync(Uri). Since this returns a Task<string> we can use it within an asynchronous function. Suppose, for example, that we wanted to do something similar to my asynchronous Task example – download a web page asynchronously and check to see if it supports XHTML 1.0, then report this into a TextBox. This could be done like so: private async void button1_Click(object sender, RoutedEventArgs e) { string url = "http://reedcopsey.com"; string content = await new WebClient().DownloadStringTaskAsync(url); this.textBox1.Text = string.Format("Page {0} supports XHTML 1.0: {1}", url, content.Contains("XHTML 1.0")); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Let’s walk through what’s happening here, step by step. By adding the async contextual keyword to the method definition, we are able to use the await keyword on our WebClient.DownloadStringTaskAsync method call. When the user clicks this button, the new method (Task<string> WebClient.DownloadStringTaskAsync(string)) is called, which returns a Task<string>. By adding the await keyword, the runtime will call this method that returns Task<string>, and execution will return to the caller at this point. This means that our UI is not blocked while the webpage is downloaded. Instead, the UI thread will “await” at this point, and let the WebClient do it’s thing asynchronously. When the WebClient finishes downloading the string, the user interface’s synchronization context will automatically be used to “pick up” where it left off, and the Task<string> returned from DownloadStringTaskAsync is automatically unwrapped and set into the content variable. At this point, we can use that and set our text box content. There are a couple of key points here: Asynchronous functions are declared with the async keyword, and contain one or more await expressions In addition to the obvious benefits of shorter, simpler code – there are some subtle but tremendous benefits in this approach. When the execution of this asynchronous function continues after the first await statement, the initial synchronization context is used to continue the execution of this function. That means that we don’t have to explicitly marshal the call that sets textbox1.Text back to the UI thread – it’s handled automatically by the language and framework! Exception handling around asynchronous method calls also just works. I’d recommend every C# developer take a look at the documentation on the new Asynchronous Programming for C# and Visual Basic page, download the Visual Studio Async CTP, and try it out.

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Integrating WIF with WCF Data Services

- by cibrax

A time ago I discussed how a custom REST Starter kit interceptor could be used to parse a SAML token in the Http Authorization header and wrap that into a ClaimsPrincipal that the WCF services could use. The thing is that code was initially created for Geneva framework, so it got deprecated quickly. I recently needed that piece of code for one of projects where I am currently working on so I decided to update it for WIF. As this interceptor can be injected in any host for WCF REST services, also represents an excellent solution for integrating claim-based security into WCF Data Services (previously known as ADO.NET Data Services). The interceptor basically expects a SAML token in the Authorization header. If a token is found, it is parsed and a new ClaimsPrincipal is initialized and injected in the WCF authorization context. public class SamlAuthenticationInterceptor : RequestInterceptor { SecurityTokenHandlerCollection handlers; public SamlAuthenticationInterceptor() : base(false) { this.handlers = FederatedAuthentication.ServiceConfiguration.SecurityTokenHandlers; } public override void ProcessRequest(ref RequestContext requestContext) { SecurityToken token = ExtractCredentials(requestContext.RequestMessage); if (token != null) { ClaimsIdentityCollection claims = handlers.ValidateToken(token); var principal = new ClaimsPrincipal(claims); InitializeSecurityContext(requestContext.RequestMessage, principal); } else { DenyAccess(ref requestContext); } } private void DenyAccess(ref RequestContext requestContext) { Message reply = Message.CreateMessage(MessageVersion.None, null); HttpResponseMessageProperty responseProperty = new HttpResponseMessageProperty() { StatusCode = HttpStatusCode.Unauthorized }; responseProperty.Headers.Add("WWW-Authenticate", String.Format("Basic realm=\"{0}\"", "")); reply.Properties[HttpResponseMessageProperty.Name] = responseProperty; requestContext.Reply(reply); requestContext = null; } private SecurityToken ExtractCredentials(Message requestMessage) { HttpRequestMessageProperty request = (HttpRequestMessageProperty) requestMessage.Properties[HttpRequestMessageProperty.Name]; string authHeader = request.Headers["Authorization"]; if (authHeader != null && authHeader.Contains("<saml")) { XmlTextReader xmlReader = new XmlTextReader(new StringReader(authHeader)); var col = SecurityTokenHandlerCollection.CreateDefaultSecurityTokenHandlerCollection(); SecurityToken token = col.ReadToken(xmlReader); return token; } return null; } private void InitializeSecurityContext(Message request, IPrincipal principal) { List<IAuthorizationPolicy> policies = new List<IAuthorizationPolicy>(); policies.Add(new PrincipalAuthorizationPolicy(principal)); ServiceSecurityContext securityContext = new ServiceSecurityContext(policies.AsReadOnly()); if (request.Properties.Security != null) { request.Properties.Security.ServiceSecurityContext = securityContext; } else { request.Properties.Security = new SecurityMessageProperty() { ServiceSecurityContext = securityContext }; } } class PrincipalAuthorizationPolicy : IAuthorizationPolicy { string id = Guid.NewGuid().ToString(); IPrincipal user; public PrincipalAuthorizationPolicy(IPrincipal user) { this.user = user; } public ClaimSet Issuer { get { return ClaimSet.System; } } public string Id { get { return this.id; } } public bool Evaluate(EvaluationContext evaluationContext, ref object state) { evaluationContext.AddClaimSet(this, new DefaultClaimSet(System.IdentityModel.Claims.Claim.CreateNameClaim(user.Identity.Name))); evaluationContext.Properties["Identities"] = new List<IIdentity>(new IIdentity[] { user.Identity }); evaluationContext.Properties["Principal"] = user; return true; } } A WCF Data Service, as any other WCF Service, contains a service host where this interceptor can be injected. The following code illustrates how that can be done in the “svc” file. <%@ ServiceHost Language="C#" Debug="true" Service="ContactsDataService" Factory="AppServiceHostFactory" %> using System; using System.ServiceModel; using System.ServiceModel.Activation; using Microsoft.ServiceModel.Web; class AppServiceHostFactory : ServiceHostFactory { protected override ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses) { WebServiceHost2 result = new WebServiceHost2(serviceType, true, baseAddresses); result.Interceptors.Add(new SamlAuthenticationInterceptor()); return result; } } WCF Data Services includes an specific WCF host of out the box (DataServiceHost). However, the service is not affected at all if you replace it with a custom one as I am doing in the code above (WebServiceHost2 is part of the REST Starter kit). Finally, the client application needs to pass the SAML token somehow to the data service. In case you are using any Http client library for consuming the data service, that’s easy to do, you only need to include the SAML token as part of the “Authorization” header. If you are using the auto-generated data service proxy, a little piece of code is needed to inject a SAML token into the DataServiceContext instance. That class provides an event “SendingRequest” that any client application can leverage to include custom code that modified the Http request before it is sent to the service. So, you can easily create an extension method for the DataServiceContext that negotiates the SAML token with an existing STS, and adds that token as part of the “Authorization” header. public static class DataServiceContextExtensions { public static void ConfigureFederatedCredentials(this DataServiceContext context, string baseStsAddress, string realm) { string address = string.Format(STSAddressFormat, baseStsAddress, realm); string token = NegotiateSecurityToken(address); context.SendingRequest += (source, args) => { args.RequestHeaders.Add("Authorization", token); }; } private string NegotiateSecurityToken(string address) { } } I left the NegociateSecurityToken method empty for this extension as it depends pretty much on how you are negotiating tokens from an existing STS. In case you want to end-to-end REST solution that involves an Http endpoint for the STS, you should definitely take a look at the Thinktecture starter STS project in codeplex.

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Searching for tasks with code – Executables and Event Handlers

Searching packages or just enumerating through all tasks is not quite as straightforward as it may first appear, mainly because of the way you can nest tasks within other containers. You can see this illustrated in the sample package below where I have used several sequence containers and loops. To complicate this further all containers types, including packages and tasks, can have event handlers which can then support the full range of nested containers again. Towards the lower right, the task called SQL In FEL also has an event handler not shown, within which is another Execute SQL Task, so that makes a total of 6 Execute SQL Tasks 6 tasks spread across the package. In my previous post about such as adding a property expressionI kept it simple and just looked at tasks at the package level, but what if you wanted to find any or all tasks in a package? For this post I've written a console program that will search a package looking at all tasks no matter how deeply nested, and check to see if the name starts with "SQL". When it finds a matching task it writes out the hierarchy by name for that task, starting with the package and working down to the task itself. The output for our sample package is shown below, note it has found all 6 tasks, including the one on the OnPreExecute event of the SQL In FEL task TaskSearch v1.0.0.0 (1.0.0.0) Copyright (C) 2009 Konesans Ltd Processing File - C:\Projects\Alpha\Packages\MyPackage.dtsx MyPackage\FOR Counter Loop\SQL In Counter Loop MyPackage\SEQ For Each Loop Wrapper\FEL Simple Loop\SQL In FEL MyPackage\SEQ For Each Loop Wrapper\FEL Simple Loop\SQL In FEL\OnPreExecute\SQL On Pre Execute for FEL SQL Task MyPackage\SEQ Top Level\SEQ Nested Lvl 1\SEQ Nested Lvl 2\SQL In Nested Lvl 2 MyPackage\SEQ Top Level\SEQ Nested Lvl 1\SQL In Nested Lvl 1 #1 MyPackage\SEQ Top Level\SEQ Nested Lvl 1\SQL In Nested Lvl 1 #2 6 matching tasks found in package. The full project and code is available for download below, but first we can walk through the project to highlight the most important sections of code. This code has been abbreviated for this description, but is complete in the download. First of all we load the package, and then start by looking at the Executables for the package. // Load the package file Application application = new Application(); using (Package package = application.LoadPackage(filename, null)) { int matchCount = 0; // Look in the package's executables ProcessExecutables(package.Executables, ref matchCount); ... // // ... // Write out final count Console.WriteLine("{0} matching tasks found in package.", matchCount); } The ProcessExecutables method is a key method, as an executable could be described as the the highest level of a working functionality or container. There are several of types of executables, such as tasks, or sequence containers and loops. To know what to do next we need to work out what type of executable we are dealing with as the abbreviated version of method shows below. private static void ProcessExecutables(Executables executables, ref int matchCount) { foreach (Executable executable in executables) { TaskHost taskHost = executable as TaskHost; if (taskHost != null) { ProcessTaskHost(taskHost, ref matchCount); ProcessEventHandlers(taskHost.EventHandlers, ref matchCount); continue; } ... // // ... ForEachLoop forEachLoop = executable as ForEachLoop; if (forEachLoop != null) { ProcessExecutables(forEachLoop.Executables, ref matchCount); ProcessEventHandlers(forEachLoop.EventHandlers, ref matchCount); continue; } } } As you can see if the executable we find is a task we then call out to our ProcessTaskHost method. As with all of our executables a task can have event handlers which themselves contain more executables such as task and loops, so we also make a call out our ProcessEventHandlers method. The other types of executables such as loops can also have event handlers as well as executables. As shown with the example for the ForEachLoop we call the same ProcessExecutables and ProcessEventHandlers methods again to drill down into the hierarchy of objects that the package may contain. This code needs to explicitly check for each type of executable (TaskHost, Sequence, ForLoop and ForEachLoop) because whilst they all have an Executables property this is not from a common base class or interface. This example was just a simple find a task by its name, so ProcessTaskHost really just does that. We also get the hierarchy of objects so we can write out for information, obviously you can adapt this method to do something more interesting such as adding a property expression. private static void ProcessTaskHost(TaskHost taskHost, ref int matchCount) { if (taskHost == null) { return; } // Check if the task matches our match name if (taskHost.Name.StartsWith(TaskNameFilter, StringComparison.OrdinalIgnoreCase)) { // Build up the full object hierarchy of the task // so we can write it out for information StringBuilder path = new StringBuilder(); DtsContainer container = taskHost; while (container != null) { path.Insert(0, container.Name); container = container.Parent; if (container != null) { path.Insert(0, "\\"); } } // Write the task path // e.g. Package\Container\Event\Task Console.WriteLine(path); Console.WriteLine(); // Increment match counter for info matchCount++; } } Just for completeness, the other processing method we covered above is for event handlers, but really that just calls back to the executables. This same method is called in our main package method, but it was omitted for brevity here. private static void ProcessEventHandlers(DtsEventHandlers eventHandlers, ref int matchCount) { foreach (DtsEventHandler eventHandler in eventHandlers) { ProcessExecutables(eventHandler.Executables, ref matchCount); } } As hopefully the code demonstrates, executables (Microsoft.SqlServer.Dts.Runtime.Executable) are the workers, but within them you can nest more executables (except for task tasks).Executables themselves can have event handlers which can in turn hold more executables. I have tried to illustrate this highlight the relationships in the following diagram. Download Sample code project TaskSearch.zip (11KB)

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