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  • Parsing an XML string containing "&#x20;" (which must be preserved)

    - by Zoodor
    I have code that is passed a string containing XML. This XML may contain one or more instances of &#x20; (an entity reference for the blank space character). I have a requirement that these references should not be resolved (i.e. they should not be replaced with an actual space character). Is there any way for me to achieve this? Basically, given a string containing the XML: <pattern value="[A-Z0-9&#x20;]" /> I do not want it to be converted to: <pattern value="[A-Z0-9 ]" /> (What I am actually trying to achieve is to simply take an XML string and write it to a "pretty-printed" file. This is having the side-effect of resolving occurrences of &#x20; in the string to a single space character, which need to be preserved. The reason for this requirement is that the written XML document must conform to an externally-defined specification.) I have tried creating a sub-class of XmlTextReader to read from the XML string and overriding the ResolveEntity() method, but this isn't called. I have also tried assigning a custom XmlResolver.

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  • Force the use of interface instead of concrete implementation in declaration (.NET)

    - by gammelgul
    In C++, you can do the following: class base_class { public: virtual void do_something() = 0; }; class derived_class : public base_class { private: virtual void do_something() { std::cout << "do_something() called"; } }; The derived_class overrides the method do_something() and makes it private. The effect is, that the only way to call this method is like this: base_class *object = new derived_class(); object->do_something(); If you declare the object as of type derived_class, you can't call the method because it's private: derived_class *object = new derived_class(); object->do_something(); // --> error C2248: '::derived_class::do_something' : cannot access private member declared in class '::derived_class' I think this is quite nice, because if you create an abstract class that is used as an interface, you can make sure that nobody accidentally declares a field as the concrete type, but always uses the interface class. Since in C# / .NET in general, you aren't allowed to narrow the access from public to private when overriding a method, is there a way to achieve a similar effect here?

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  • An Introduction to ASP.NET Web API

    - by Rick Strahl
    Microsoft recently released ASP.NET MVC 4.0 and .NET 4.5 and along with it, the brand spanking new ASP.NET Web API. Web API is an exciting new addition to the ASP.NET stack that provides a new, well-designed HTTP framework for creating REST and AJAX APIs (API is Microsoft’s new jargon for a service, in case you’re wondering). Although Web API ships and installs with ASP.NET MVC 4, you can use Web API functionality in any ASP.NET project, including WebForms, WebPages and MVC or just a Web API by itself. And you can also self-host Web API in your own applications from Console, Desktop or Service applications. If you're interested in a high level overview on what ASP.NET Web API is and how it fits into the ASP.NET stack you can check out my previous post: Where does ASP.NET Web API fit? In the following article, I'll focus on a practical, by example introduction to ASP.NET Web API. All the code discussed in this article is available in GitHub: https://github.com/RickStrahl/AspNetWebApiArticle [republished from my Code Magazine Article and updated for RTM release of ASP.NET Web API] Getting Started To start I’ll create a new empty ASP.NET application to demonstrate that Web API can work with any kind of ASP.NET project. Although you can create a new project based on the ASP.NET MVC/Web API template to quickly get up and running, I’ll take you through the manual setup process, because one common use case is to add Web API functionality to an existing ASP.NET application. This process describes the steps needed to hook up Web API to any ASP.NET 4.0 application. Start by creating an ASP.NET Empty Project. Then create a new folder in the project called Controllers. Add a Web API Controller Class Once you have any kind of ASP.NET project open, you can add a Web API Controller class to it. Web API Controllers are very similar to MVC Controller classes, but they work in any kind of project. Add a new item to this folder by using the Add New Item option in Visual Studio and choose Web API Controller Class, as shown in Figure 1. Figure 1: This is how you create a new Controller Class in Visual Studio   Make sure that the name of the controller class includes Controller at the end of it, which is required in order for Web API routing to find it. Here, the name for the class is AlbumApiController. For this example, I’ll use a Music Album model to demonstrate basic behavior of Web API. The model consists of albums and related songs where an album has properties like Name, Artist and YearReleased and a list of songs with a SongName and SongLength as well as an AlbumId that links it to the album. You can find the code for the model (and the rest of these samples) on Github. To add the file manually, create a new folder called Model, and add a new class Album.cs and copy the code into it. There’s a static AlbumData class with a static CreateSampleAlbumData() method that creates a short list of albums on a static .Current that I’ll use for the examples. Before we look at what goes into the controller class though, let’s hook up routing so we can access this new controller. Hooking up Routing in Global.asax To start, I need to perform the one required configuration task in order for Web API to work: I need to configure routing to the controller. Like MVC, Web API uses routing to provide clean, extension-less URLs to controller methods. Using an extension method to ASP.NET’s static RouteTable class, you can use the MapHttpRoute() (in the System.Web.Http namespace) method to hook-up the routing during Application_Start in global.asax.cs shown in Listing 1.using System; using System.Web.Routing; using System.Web.Http; namespace AspNetWebApi { public class Global : System.Web.HttpApplication { protected void Application_Start(object sender, EventArgs e) { RouteTable.Routes.MapHttpRoute( name: "AlbumVerbs", routeTemplate: "albums/{title}", defaults: new { symbol = RouteParameter.Optional, controller="AlbumApi" } ); } } } This route configures Web API to direct URLs that start with an albums folder to the AlbumApiController class. Routing in ASP.NET is used to create extensionless URLs and allows you to map segments of the URL to specific Route Value parameters. A route parameter, with a name inside curly brackets like {name}, is mapped to parameters on the controller methods. Route parameters can be optional, and there are two special route parameters – controller and action – that determine the controller to call and the method to activate respectively. HTTP Verb Routing Routing in Web API can route requests by HTTP Verb in addition to standard {controller},{action} routing. For the first examples, I use HTTP Verb routing, as shown Listing 1. Notice that the route I’ve defined does not include an {action} route value or action value in the defaults. Rather, Web API can use the HTTP Verb in this route to determine the method to call the controller, and a GET request maps to any method that starts with Get. So methods called Get() or GetAlbums() are matched by a GET request and a POST request maps to a Post() or PostAlbum(). Web API matches a method by name and parameter signature to match a route, query string or POST values. In lieu of the method name, the [HttpGet,HttpPost,HttpPut,HttpDelete, etc] attributes can also be used to designate the accepted verbs explicitly if you don’t want to follow the verb naming conventions. Although HTTP Verb routing is a good practice for REST style resource APIs, it’s not required and you can still use more traditional routes with an explicit {action} route parameter. When {action} is supplied, the HTTP verb routing is ignored. I’ll talk more about alternate routes later. When you’re finished with initial creation of files, your project should look like Figure 2.   Figure 2: The initial project has the new API Controller Album model   Creating a small Album Model Now it’s time to create some controller methods to serve data. For these examples, I’ll use a very simple Album and Songs model to play with, as shown in Listing 2. public class Song { public string AlbumId { get; set; } [Required, StringLength(80)] public string SongName { get; set; } [StringLength(5)] public string SongLength { get; set; } } public class Album { public string Id { get; set; } [Required, StringLength(80)] public string AlbumName { get; set; } [StringLength(80)] public string Artist { get; set; } public int YearReleased { get; set; } public DateTime Entered { get; set; } [StringLength(150)] public string AlbumImageUrl { get; set; } [StringLength(200)] public string AmazonUrl { get; set; } public virtual List<Song> Songs { get; set; } public Album() { Songs = new List<Song>(); Entered = DateTime.Now; // Poor man's unique Id off GUID hash Id = Guid.NewGuid().GetHashCode().ToString("x"); } public void AddSong(string songName, string songLength = null) { this.Songs.Add(new Song() { AlbumId = this.Id, SongName = songName, SongLength = songLength }); } } Once the model has been created, I also added an AlbumData class that generates some static data in memory that is loaded onto a static .Current member. The signature of this class looks like this and that's what I'll access to retrieve the base data:public static class AlbumData { // sample data - static list public static List<Album> Current = CreateSampleAlbumData(); /// <summary> /// Create some sample data /// </summary> /// <returns></returns> public static List<Album> CreateSampleAlbumData() { … }} You can check out the full code for the data generation online. Creating an AlbumApiController Web API shares many concepts of ASP.NET MVC, and the implementation of your API logic is done by implementing a subclass of the System.Web.Http.ApiController class. Each public method in the implemented controller is a potential endpoint for the HTTP API, as long as a matching route can be found to invoke it. The class name you create should end in Controller, which is how Web API matches the controller route value to figure out which class to invoke. Inside the controller you can implement methods that take standard .NET input parameters and return .NET values as results. Web API’s binding tries to match POST data, route values, form values or query string values to your parameters. Because the controller is configured for HTTP Verb based routing (no {action} parameter in the route), any methods that start with Getxxxx() are called by an HTTP GET operation. You can have multiple methods that match each HTTP Verb as long as the parameter signatures are different and can be matched by Web API. In Listing 3, I create an AlbumApiController with two methods to retrieve a list of albums and a single album by its title .public class AlbumApiController : ApiController { public IEnumerable<Album> GetAlbums() { var albums = AlbumData.Current.OrderBy(alb => alb.Artist); return albums; } public Album GetAlbum(string title) { var album = AlbumData.Current .SingleOrDefault(alb => alb.AlbumName.Contains(title)); return album; }} To access the first two requests, you can use the following URLs in your browser: http://localhost/aspnetWebApi/albumshttp://localhost/aspnetWebApi/albums/Dirty%20Deeds Note that you’re not specifying the actions of GetAlbum or GetAlbums in these URLs. Instead Web API’s routing uses HTTP GET verb to route to these methods that start with Getxxx() with the first mapping to the parameterless GetAlbums() method and the latter to the GetAlbum(title) method that receives the title parameter mapped as optional in the route. Content Negotiation When you access any of the URLs above from a browser, you get either an XML or JSON result returned back. The album list result for Chrome 17 and Internet Explorer 9 is shown Figure 3. Figure 3: Web API responses can vary depending on the browser used, demonstrating Content Negotiation in action as these two browsers send different HTTP Accept headers.   Notice that the results are not the same: Chrome returns an XML response and IE9 returns a JSON response. Whoa, what’s going on here? Shouldn’t we see the same result in both browsers? Actually, no. Web API determines what type of content to return based on Accept headers. HTTP clients, like browsers, use Accept headers to specify what kind of content they’d like to see returned. Browsers generally ask for HTML first, followed by a few additional content types. Chrome (and most other major browsers) ask for: Accept: text/html, application/xhtml+xml,application/xml; q=0.9,*/*;q=0.8 IE9 asks for: Accept: text/html, application/xhtml+xml, */* Note that Chrome’s Accept header includes application/xml, which Web API finds in its list of supported media types and returns an XML response. IE9 does not include an Accept header type that works on Web API by default, and so it returns the default format, which is JSON. This is an important and very useful feature that was missing from any previous Microsoft REST tools: Web API automatically switches output formats based on HTTP Accept headers. Nowhere in the server code above do you have to explicitly specify the output format. Rather, Web API determines what format the client is requesting based on the Accept headers and automatically returns the result based on the available formatters. This means that a single method can handle both XML and JSON results.. Using this simple approach makes it very easy to create a single controller method that can return JSON, XML, ATOM or even OData feeds by providing the appropriate Accept header from the client. By default you don’t have to worry about the output format in your code. Note that you can still specify an explicit output format if you choose, either globally by overriding the installed formatters, or individually by returning a lower level HttpResponseMessage instance and setting the formatter explicitly. More on that in a minute. Along the same lines, any content sent to the server via POST/PUT is parsed by Web API based on the HTTP Content-type of the data sent. The same formats allowed for output are also allowed on input. Again, you don’t have to do anything in your code – Web API automatically performs the deserialization from the content. Accessing Web API JSON Data with jQuery A very common scenario for Web API endpoints is to retrieve data for AJAX calls from the Web browser. Because JSON is the default format for Web API, it’s easy to access data from the server using jQuery and its getJSON() method. This example receives the albums array from GetAlbums() and databinds it into the page using knockout.js.$.getJSON("albums/", function (albums) { // make knockout template visible $(".album").show(); // create view object and attach array var view = { albums: albums }; ko.applyBindings(view); }); Figure 4 shows this and the next example’s HTML output. You can check out the complete HTML and script code at http://goo.gl/Ix33C (.html) and http://goo.gl/tETlg (.js). Figu Figure 4: The Album Display sample uses JSON data loaded from Web API.   The result from the getJSON() call is a JavaScript object of the server result, which comes back as a JavaScript array. In the code, I use knockout.js to bind this array into the UI, which as you can see, requires very little code, instead using knockout’s data-bind attributes to bind server data to the UI. Of course, this is just one way to use the data – it’s entirely up to you to decide what to do with the data in your client code. Along the same lines, I can retrieve a single album to display when the user clicks on an album. The response returns the album information and a child array with all the songs. The code to do this is very similar to the last example where we pulled the albums array:$(".albumlink").live("click", function () { var id = $(this).data("id"); // title $.getJSON("albums/" + id, function (album) { ko.applyBindings(album, $("#divAlbumDialog")[0]); $("#divAlbumDialog").show(); }); }); Here the URL looks like this: /albums/Dirty%20Deeds, where the title is the ID captured from the clicked element’s data ID attribute. Explicitly Overriding Output Format When Web API automatically converts output using content negotiation, it does so by matching Accept header media types to the GlobalConfiguration.Configuration.Formatters and the SupportedMediaTypes of each individual formatter. You can add and remove formatters to globally affect what formats are available and it’s easy to create and plug in custom formatters.The example project includes a JSONP formatter that can be plugged in to provide JSONP support for requests that have a callback= querystring parameter. Adding, removing or replacing formatters is a global option you can use to manipulate content. It’s beyond the scope of this introduction to show how it works, but you can review the sample code or check out my blog entry on the subject (http://goo.gl/UAzaR). If automatic processing is not desirable in a particular Controller method, you can override the response output explicitly by returning an HttpResponseMessage instance. HttpResponseMessage is similar to ActionResult in ASP.NET MVC in that it’s a common way to return an abstract result message that contains content. HttpResponseMessage s parsed by the Web API framework using standard interfaces to retrieve the response data, status code, headers and so on[MS2] . Web API turns every response – including those Controller methods that return static results – into HttpResponseMessage instances. Explicitly returning an HttpResponseMessage instance gives you full control over the output and lets you mostly bypass WebAPI’s post-processing of the HTTP response on your behalf. HttpResponseMessage allows you to customize the response in great detail. Web API’s attention to detail in the HTTP spec really shows; many HTTP options are exposed as properties and enumerations with detailed IntelliSense comments. Even if you’re new to building REST-based interfaces, the API guides you in the right direction for returning valid responses and response codes. For example, assume that I always want to return JSON from the GetAlbums() controller method and ignore the default media type content negotiation. To do this, I can adjust the output format and headers as shown in Listing 4.public HttpResponseMessage GetAlbums() { var albums = AlbumData.Current.OrderBy(alb => alb.Artist); // Create a new HttpResponse with Json Formatter explicitly var resp = new HttpResponseMessage(HttpStatusCode.OK); resp.Content = new ObjectContent<IEnumerable<Album>>( albums, new JsonMediaTypeFormatter()); // Get Default Formatter based on Content Negotiation //var resp = Request.CreateResponse<IEnumerable<Album>>(HttpStatusCode.OK, albums); resp.Headers.ConnectionClose = true; resp.Headers.CacheControl = new CacheControlHeaderValue(); resp.Headers.CacheControl.Public = true; return resp; } This example returns the same IEnumerable<Album> value, but it wraps the response into an HttpResponseMessage so you can control the entire HTTP message result including the headers, formatter and status code. In Listing 4, I explicitly specify the formatter using the JsonMediaTypeFormatter to always force the content to JSON.  If you prefer to use the default content negotiation with HttpResponseMessage results, you can create the Response instance using the Request.CreateResponse method:var resp = Request.CreateResponse<IEnumerable<Album>>(HttpStatusCode.OK, albums); This provides you an HttpResponse object that's pre-configured with the default formatter based on Content Negotiation. Once you have an HttpResponse object you can easily control most HTTP aspects on this object. What's sweet here is that there are many more detailed properties on HttpResponse than the core ASP.NET Response object, with most options being explicitly configurable with enumerations that make it easy to pick the right headers and response codes from a list of valid codes. It makes HTTP features available much more discoverable even for non-hardcore REST/HTTP geeks. Non-Serialized Results The output returned doesn’t have to be a serialized value but can also be raw data, like strings, binary data or streams. You can use the HttpResponseMessage.Content object to set a number of common Content classes. Listing 5 shows how to return a binary image using the ByteArrayContent class from a Controller method. [HttpGet] public HttpResponseMessage AlbumArt(string title) { var album = AlbumData.Current.FirstOrDefault(abl => abl.AlbumName.StartsWith(title)); if (album == null) { var resp = Request.CreateResponse<ApiMessageError>( HttpStatusCode.NotFound, new ApiMessageError("Album not found")); return resp; } // kinda silly - we would normally serve this directly // but hey - it's a demo. var http = new WebClient(); var imageData = http.DownloadData(album.AlbumImageUrl); // create response and return var result = new HttpResponseMessage(HttpStatusCode.OK); result.Content = new ByteArrayContent(imageData); result.Content.Headers.ContentType = new MediaTypeHeaderValue("image/jpeg"); return result; } The image retrieval from Amazon is contrived, but it shows how to return binary data using ByteArrayContent. It also demonstrates that you can easily return multiple types of content from a single controller method, which is actually quite common. If an error occurs - such as a resource can’t be found or a validation error – you can return an error response to the client that’s very specific to the error. In GetAlbumArt(), if the album can’t be found, we want to return a 404 Not Found status (and realistically no error, as it’s an image). Note that if you are not using HTTP Verb-based routing or not accessing a method that starts with Get/Post etc., you have to specify one or more HTTP Verb attributes on the method explicitly. Here, I used the [HttpGet] attribute to serve the image. Another option to handle the error could be to return a fixed placeholder image if no album could be matched or the album doesn’t have an image. When returning an error code, you can also return a strongly typed response to the client. For example, you can set the 404 status code and also return a custom error object (ApiMessageError is a class I defined) like this:return Request.CreateResponse<ApiMessageError>( HttpStatusCode.NotFound, new ApiMessageError("Album not found") );   If the album can be found, the image will be returned. The image is downloaded into a byte[] array, and then assigned to the result’s Content property. I created a new ByteArrayContent instance and assigned the image’s bytes and the content type so that it displays properly in the browser. There are other content classes available: StringContent, StreamContent, ByteArrayContent, MultipartContent, and ObjectContent are at your disposal to return just about any kind of content. You can create your own Content classes if you frequently return custom types and handle the default formatter assignments that should be used to send the data out . Although HttpResponseMessage results require more code than returning a plain .NET value from a method, it allows much more control over the actual HTTP processing than automatic processing. It also makes it much easier to test your controller methods as you get a response object that you can check for specific status codes and output messages rather than just a result value. Routing Again Ok, let’s get back to the image example. Using the original routing we have setup using HTTP Verb routing there's no good way to serve the image. In order to return my album art image I’d like to use a URL like this: http://localhost/aspnetWebApi/albums/Dirty%20Deeds/image In order to create a URL like this, I have to create a new Controller because my earlier routes pointed to the AlbumApiController using HTTP Verb routing. HTTP Verb based routing is great for representing a single set of resources such as albums. You can map operations like add, delete, update and read easily using HTTP Verbs. But you cannot mix action based routing into a an HTTP Verb routing controller - you can only map HTTP Verbs and each method has to be unique based on parameter signature. You can't have multiple GET operations to methods with the same signature. So GetImage(string id) and GetAlbum(string title) are in conflict in an HTTP GET routing scenario. In fact, I was unable to make the above Image URL work with any combination of HTTP Verb plus Custom routing using the single Albums controller. There are number of ways around this, but all involve additional controllers.  Personally, I think it’s easier to use explicit Action routing and then add custom routes if you need to simplify your URLs further. So in order to accommodate some of the other examples, I created another controller – AlbumRpcApiController – to handle all requests that are explicitly routed via actions (/albums/rpc/AlbumArt) or are custom routed with explicit routes defined in the HttpConfiguration. I added the AlbumArt() method to this new AlbumRpcApiController class. For the image URL to work with the new AlbumRpcApiController, you need a custom route placed before the default route from Listing 1.RouteTable.Routes.MapHttpRoute( name: "AlbumRpcApiAction", routeTemplate: "albums/rpc/{action}/{title}", defaults: new { title = RouteParameter.Optional, controller = "AlbumRpcApi", action = "GetAblums" } ); Now I can use either of the following URLs to access the image: Custom route: (/albums/rpc/{title}/image)http://localhost/aspnetWebApi/albums/PowerAge/image Action route: (/albums/rpc/action/{title})http://localhost/aspnetWebAPI/albums/rpc/albumart/PowerAge Sending Data to the Server To send data to the server and add a new album, you can use an HTTP POST operation. Since I’m using HTTP Verb-based routing in the original AlbumApiController, I can implement a method called PostAlbum()to accept a new album from the client. Listing 6 shows the Web API code to add a new album.public HttpResponseMessage PostAlbum(Album album) { if (!this.ModelState.IsValid) { // my custom error class var error = new ApiMessageError() { message = "Model is invalid" }; // add errors into our client error model for client foreach (var prop in ModelState.Values) { var modelError = prop.Errors.FirstOrDefault(); if (!string.IsNullOrEmpty(modelError.ErrorMessage)) error.errors.Add(modelError.ErrorMessage); else error.errors.Add(modelError.Exception.Message); } return Request.CreateResponse<ApiMessageError>(HttpStatusCode.Conflict, error); } // update song id which isn't provided foreach (var song in album.Songs) song.AlbumId = album.Id; // see if album exists already var matchedAlbum = AlbumData.Current .SingleOrDefault(alb => alb.Id == album.Id || alb.AlbumName == album.AlbumName); if (matchedAlbum == null) AlbumData.Current.Add(album); else matchedAlbum = album; // return a string to show that the value got here var resp = Request.CreateResponse(HttpStatusCode.OK, string.Empty); resp.Content = new StringContent(album.AlbumName + " " + album.Entered.ToString(), Encoding.UTF8, "text/plain"); return resp; } The PostAlbum() method receives an album parameter, which is automatically deserialized from the POST buffer the client sent. The data passed from the client can be either XML or JSON. Web API automatically figures out what format it needs to deserialize based on the content type and binds the content to the album object. Web API uses model binding to bind the request content to the parameter(s) of controller methods. Like MVC you can check the model by looking at ModelState.IsValid. If it’s not valid, you can run through the ModelState.Values collection and check each binding for errors. Here I collect the error messages into a string array that gets passed back to the client via the result ApiErrorMessage object. When a binding error occurs, you’ll want to return an HTTP error response and it’s best to do that with an HttpResponseMessage result. In Listing 6, I used a custom error class that holds a message and an array of detailed error messages for each binding error. I used this object as the content to return to the client along with my Conflict HTTP Status Code response. If binding succeeds, the example returns a string with the name and date entered to demonstrate that you captured the data. Normally, a method like this should return a Boolean or no response at all (HttpStatusCode.NoConent). The sample uses a simple static list to hold albums, so once you’ve added the album using the Post operation, you can hit the /albums/ URL to see that the new album was added. The client jQuery code to call the POST operation from the client with jQuery is shown in Listing 7. var id = new Date().getTime().toString(); var album = { "Id": id, "AlbumName": "Power Age", "Artist": "AC/DC", "YearReleased": 1977, "Entered": "2002-03-11T18:24:43.5580794-10:00", "AlbumImageUrl": http://ecx.images-amazon.com/images/…, "AmazonUrl": http://www.amazon.com/…, "Songs": [ { "SongName": "Rock 'n Roll Damnation", "SongLength": 3.12}, { "SongName": "Downpayment Blues", "SongLength": 4.22 }, { "SongName": "Riff Raff", "SongLength": 2.42 } ] } $.ajax( { url: "albums/", type: "POST", contentType: "application/json", data: JSON.stringify(album), processData: false, beforeSend: function (xhr) { // not required since JSON is default output xhr.setRequestHeader("Accept", "application/json"); }, success: function (result) { // reload list of albums page.loadAlbums(); }, error: function (xhr, status, p3, p4) { var err = "Error"; if (xhr.responseText && xhr.responseText[0] == "{") err = JSON.parse(xhr.responseText).message; alert(err); } }); The code in Listing 7 creates an album object in JavaScript to match the structure of the .NET Album class. This object is passed to the $.ajax() function to send to the server as POST. The data is turned into JSON and the content type set to application/json so that the server knows what to convert when deserializing in the Album instance. The jQuery code hooks up success and failure events. Success returns the result data, which is a string that’s echoed back with an alert box. If an error occurs, jQuery returns the XHR instance and status code. You can check the XHR to see if a JSON object is embedded and if it is, you can extract it by de-serializing it and accessing the .message property. REST standards suggest that updates to existing resources should use PUT operations. REST standards aside, I’m not a big fan of separating out inserts and updates so I tend to have a single method that handles both. But if you want to follow REST suggestions, you can create a PUT method that handles updates by forwarding the PUT operation to the POST method:public HttpResponseMessage PutAlbum(Album album) { return PostAlbum(album); } To make the corresponding $.ajax() call, all you have to change from Listing 7 is the type: from POST to PUT. Model Binding with UrlEncoded POST Variables In the example in Listing 7 I used JSON objects to post a serialized object to a server method that accepted an strongly typed object with the same structure, which is a common way to send data to the server. However, Web API supports a number of different ways that data can be received by server methods. For example, another common way is to use plain UrlEncoded POST  values to send to the server. Web API supports Model Binding that works similar (but not the same) as MVC's model binding where POST variables are mapped to properties of object parameters of the target method. This is actually quite common for AJAX calls that want to avoid serialization and the potential requirement of a JSON parser on older browsers. For example, using jQUery you might use the $.post() method to send a new album to the server (albeit one without songs) using code like the following:$.post("albums/",{AlbumName: "Dirty Deeds", YearReleased: 1976 … },albumPostCallback); Although the code looks very similar to the client code we used before passing JSON, here the data passed is URL encoded values (AlbumName=Dirty+Deeds&YearReleased=1976 etc.). Web API then takes this POST data and maps each of the POST values to the properties of the Album object in the method's parameter. Although the client code is different the server can both handle the JSON object, or the UrlEncoded POST values. Dynamic Access to POST Data There are also a few options available to dynamically access POST data, if you know what type of data you're dealing with. If you have POST UrlEncoded values, you can dynamically using a FormsDataCollection:[HttpPost] public string PostAlbum(FormDataCollection form) { return string.Format("{0} - released {1}", form.Get("AlbumName"),form.Get("RearReleased")); } The FormDataCollection is a very simple object, that essentially provides the same functionality as Request.Form[] in ASP.NET. Request.Form[] still works if you're running hosted in an ASP.NET application. However as a general rule, while ASP.NET's functionality is always available when running Web API hosted inside of an  ASP.NET application, using the built in classes specific to Web API makes it possible to run Web API applications in a self hosted environment outside of ASP.NET. If your client is sending JSON to your server, and you don't want to map the JSON to a strongly typed object because you only want to retrieve a few simple values, you can also accept a JObject parameter in your API methods:[HttpPost] public string PostAlbum(JObject jsonData) { dynamic json = jsonData; JObject jalbum = json.Album; JObject juser = json.User; string token = json.UserToken; var album = jalbum.ToObject<Album>(); var user = juser.ToObject<User>(); return String.Format("{0} {1} {2}", album.AlbumName, user.Name, token); } There quite a few options available to you to receive data with Web API, which gives you more choices for the right tool for the job. Unfortunately one shortcoming of Web API is that POST data is always mapped to a single parameter. This means you can't pass multiple POST parameters to methods that receive POST data. It's possible to accept multiple parameters, but only one can map to the POST content - the others have to come from the query string or route values. I have a couple of Blog POSTs that explain what works and what doesn't here: Passing multiple POST parameters to Web API Controller Methods Mapping UrlEncoded POST Values in ASP.NET Web API   Handling Delete Operations Finally, to round out the server API code of the album example we've been discussin, here’s the DELETE verb controller method that allows removal of an album by its title:public HttpResponseMessage DeleteAlbum(string title) { var matchedAlbum = AlbumData.Current.Where(alb => alb.AlbumName == title) .SingleOrDefault(); if (matchedAlbum == null) return new HttpResponseMessage(HttpStatusCode.NotFound); AlbumData.Current.Remove(matchedAlbum); return new HttpResponseMessage(HttpStatusCode.NoContent); } To call this action method using jQuery, you can use:$(".removeimage").live("click", function () { var $el = $(this).parent(".album"); var txt = $el.find("a").text(); $.ajax({ url: "albums/" + encodeURIComponent(txt), type: "Delete", success: function (result) { $el.fadeOut().remove(); }, error: jqError }); }   Note the use of the DELETE verb in the $.ajax() call, which routes to DeleteAlbum on the server. DELETE is a non-content operation, so you supply a resource ID (the title) via route value or the querystring. Routing Conflicts In all requests with the exception of the AlbumArt image example shown so far, I used HTTP Verb routing that I set up in Listing 1. HTTP Verb Routing is a recommendation that is in line with typical REST access to HTTP resources. However, it takes quite a bit of effort to create REST-compliant API implementations based only on HTTP Verb routing only. You saw one example that didn’t really fit – the return of an image where I created a custom route albums/{title}/image that required creation of a second controller and a custom route to work. HTTP Verb routing to a controller does not mix with custom or action routing to the same controller because of the limited mapping of HTTP verbs imposed by HTTP Verb routing. To understand some of the problems with verb routing, let’s look at another example. Let’s say you create a GetSortableAlbums() method like this and add it to the original AlbumApiController accessed via HTTP Verb routing:[HttpGet] public IQueryable<Album> SortableAlbums() { var albums = AlbumData.Current; // generally should be done only on actual queryable results (EF etc.) // Done here because we're running with a static list but otherwise might be slow return albums.AsQueryable(); } If you compile this code and try to now access the /albums/ link, you get an error: Multiple Actions were found that match the request. HTTP Verb routing only allows access to one GET operation per parameter/route value match. If more than one method exists with the same parameter signature, it doesn’t work. As I mentioned earlier for the image display, the only solution to get this method to work is to throw it into another controller. Because I already set up the AlbumRpcApiController I can add the method there. First, I should rename the method to SortableAlbums() so I’m not using a Get prefix for the method. This also makes the action parameter look cleaner in the URL - it looks less like a method and more like a noun. I can then create a new route that handles direct-action mapping:RouteTable.Routes.MapHttpRoute( name: "AlbumRpcApiAction", routeTemplate: "albums/rpc/{action}/{title}", defaults: new { title = RouteParameter.Optional, controller = "AlbumRpcApi", action = "GetAblums" } ); As I am explicitly adding a route segment – rpc – into the route template, I can now reference explicit methods in the Web API controller using URLs like this: http://localhost/AspNetWebApi/rpc/SortableAlbums Error Handling I’ve already done some minimal error handling in the examples. For example in Listing 6, I detected some known-error scenarios like model validation failing or a resource not being found and returning an appropriate HttpResponseMessage result. But what happens if your code just blows up or causes an exception? If you have a controller method, like this:[HttpGet] public void ThrowException() { throw new UnauthorizedAccessException("Unauthorized Access Sucka"); } You can call it with this: http://localhost/AspNetWebApi/albums/rpc/ThrowException The default exception handling displays a 500-status response with the serialized exception on the local computer only. When you connect from a remote computer, Web API throws back a 500  HTTP Error with no data returned (IIS then adds its HTML error page). The behavior is configurable in the GlobalConfiguration:GlobalConfiguration .Configuration .IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Never; If you want more control over your error responses sent from code, you can throw explicit error responses yourself using HttpResponseException. When you throw an HttpResponseException the response parameter is used to generate the output for the Controller action. [HttpGet] public void ThrowError() { var resp = Request.CreateResponse<ApiMessageError>( HttpStatusCode.BadRequest, new ApiMessageError("Your code stinks!")); throw new HttpResponseException(resp); } Throwing an HttpResponseException stops the processing of the controller method and immediately returns the response you passed to the exception. Unlike other Exceptions fired inside of WebAPI, HttpResponseException bypasses the Exception Filters installed and instead just outputs the response you provide. In this case, the serialized ApiMessageError result string is returned in the default serialization format – XML or JSON. You can pass any content to HttpResponseMessage, which includes creating your own exception objects and consistently returning error messages to the client. Here’s a small helper method on the controller that you might use to send exception info back to the client consistently:private void ThrowSafeException(string message, HttpStatusCode statusCode = HttpStatusCode.BadRequest) { var errResponse = Request.CreateResponse<ApiMessageError>(statusCode, new ApiMessageError() { message = message }); throw new HttpResponseException(errResponse); } You can then use it to output any captured errors from code:[HttpGet] public void ThrowErrorSafe() { try { List<string> list = null; list.Add("Rick"); } catch (Exception ex) { ThrowSafeException(ex.Message); } }   Exception Filters Another more global solution is to create an Exception Filter. Filters in Web API provide the ability to pre- and post-process controller method operations. An exception filter looks at all exceptions fired and then optionally creates an HttpResponseMessage result. Listing 8 shows an example of a basic Exception filter implementation.public class UnhandledExceptionFilter : ExceptionFilterAttribute { public override void OnException(HttpActionExecutedContext context) { HttpStatusCode status = HttpStatusCode.InternalServerError; var exType = context.Exception.GetType(); if (exType == typeof(UnauthorizedAccessException)) status = HttpStatusCode.Unauthorized; else if (exType == typeof(ArgumentException)) status = HttpStatusCode.NotFound; var apiError = new ApiMessageError() { message = context.Exception.Message }; // create a new response and attach our ApiError object // which now gets returned on ANY exception result var errorResponse = context.Request.CreateResponse<ApiMessageError>(status, apiError); context.Response = errorResponse; base.OnException(context); } } Exception Filter Attributes can be assigned to an ApiController class like this:[UnhandledExceptionFilter] public class AlbumRpcApiController : ApiController or you can globally assign it to all controllers by adding it to the HTTP Configuration's Filters collection:GlobalConfiguration.Configuration.Filters.Add(new UnhandledExceptionFilter()); The latter is a great way to get global error trapping so that all errors (short of hard IIS errors and explicit HttpResponseException errors) return a valid error response that includes error information in the form of a known-error object. Using a filter like this allows you to throw an exception as you normally would and have your filter create a response in the appropriate output format that the client expects. For example, an AJAX application can on failure expect to see a JSON error result that corresponds to the real error that occurred rather than a 500 error along with HTML error page that IIS throws up. You can even create some custom exceptions so you can differentiate your own exceptions from unhandled system exceptions - you often don't want to display error information from 'unknown' exceptions as they may contain sensitive system information or info that's not generally useful to users of your application/site. This is just one example of how ASP.NET Web API is configurable and extensible. Exception filters are just one example of how you can plug-in into the Web API request flow to modify output. Many more hooks exist and I’ll take a closer look at extensibility in Part 2 of this article in the future. Summary Web API is a big improvement over previous Microsoft REST and AJAX toolkits. The key features to its usefulness are its ease of use with simple controller based logic, familiar MVC-style routing, low configuration impact, extensibility at all levels and tight attention to exposing and making HTTP semantics easily discoverable and easy to use. Although none of the concepts used in Web API are new or radical, Web API combines the best of previous platforms into a single framework that’s highly functional, easy to work with, and extensible to boot. I think that Microsoft has hit a home run with Web API. Related Resources Where does ASP.NET Web API fit? Sample Source Code on GitHub Passing multiple POST parameters to Web API Controller Methods Mapping UrlEncoded POST Values in ASP.NET Web API Creating a JSONP Formatter for ASP.NET Web API Removing the XML Formatter from ASP.NET Web API Applications© Rick Strahl, West Wind Technologies, 2005-2012Posted in Web Api   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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  • Looking into ASP.Net MVC 4.0 Mobile Development - part 1

    - by nikolaosk
    In this post I will be looking how ASP.Net MVC 4.0 helps us to create web solutions that target mobile devices.We all experience the magic that is the World Wide Web through mobile devices. Millions of people around the world, use tablets and smartphones to view the contents of websites,e-shops and portals.ASP.Net MVC 4.0 includes a new mobile project template and the ability to render a different set of views for different types of devices.There is a new feature that is called browser overriding which allows us to control exactly what a user is going to see from your web application regardless of what type of device he is using.In order to follow along this post you must have Visual Studio 2012 and .Net Framework 4.5 installed in your machine.Download and install VS 2012 using this link.My machine runs on Windows 8 and Visual Studio 2012 works just fine.It will work fine in Windows 7 as well so do not worry if you do not have the latest Microsoft operating system.1) Launch VS 2012 and create a new Web Forms application by going to File - >New Project - > ASP.Net MVC 4 Web Application and then click OKHave a look at the picture below  2) From the available templates select Mobile Application and then click OK.Have a look at the picture below 3) When I run the application I get the mobile view of the page. I would like to show you what a typical ASP.Net MVC 4.0 application looks like. So I will create a new simple ASP.Net MVC 4.0 Web Application. When I run the application I get the normal page view.Have a look at the picture below.On the left is the mobile view and on the right the normal view. As you can see we have more or less the same content in our mobile application (log in,register) compared with the normal ASP.Net MVC 4.0 application but it is optimised for mobile devices. 4) Let me explain how and when the mobile view is selected and finally rendered.There is a feature in MVC 4.0 that is called Display Modes and with this feature the runtime will select a view.If we have 2 views e.g contact.mobile.cshtml and contact.cshtml in our application the Controller at some point will instruct the runtime to select and render a view named contact.The runtime will look at the browser making the request and will determine if it is a mobile browser or a desktop browser. So if there is a request from my IPhone Safari browser for a particular site, if there is a mobile view the MVC 4.0 will select it and render it. If there is not a mobile view, the normal view will be rendered.5) In the  ASP.Net MVC 4.0 (Internet application) I created earlier (not the first project which was a mobile one) I can run it once more and see how it looks on the browser. If I want to view it with a mobile browser I must download one emulator like Opera Mobile.You can download Opera Mobile hereWhen I run the application I get the same view in both the desktop and the mobile browser. That was to be expected. Have a look at the picture below 6) Then I create another version of the _Layout.mobile.cshtml view in the Shared folder.I simply copy and paste the _Layout.cshtml  into the same folder and then rename it to _Layout.mobile.cshtml and then just alter the contents of the _Layout.mobile.cshtml.When I run again the application I get a different view on the desktop browser and a different one on the Opera mobile browser.Have a look at the picture below ?he Controller will instruct the ASP.Net runtime to select and render a view named _Layout.mobile.cshtml when the request will come from a mobile browser.?he runtime knows that a browser is a mobile one through the ASP.Net browser capability provider. Hope it helps!!!

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  • Silverlight Cream for March 26, 2010 -- #821

    - by Dave Campbell
    In this Issue: Max Paulousky, Christian Schormann, John Papa, Phani Raj, David Anson(-2-, -3-), Brad Abrams(-2-), and Jeff Wilcox(-2-, -3-). Shoutouts: Jeff Wilcox posted his material from mix and some preview TestFramework bits: Unit Testing Silverlight & Windows Phone Applications – talk now online At MIX10, Jeff Wilcox demo'd an app called "Peppermint"... here's the bleeding edge demo: “Peppermint” MIX demo sources Erik Mork and Co. have put out their weekly This Week In Silverlight 3.25.2010 Brad Abrams has all his materials posted for his MIX10 session Mix2010: Search Engine Optimization (SEO) for Microsoft Silverlight... including play-by-play of the demo and all source. Do you use Rooler? Well you should! Watch a video Pete Brown did with Pete Blois on Expression Blend, Windows Phone, Rooler Interested in Silverlight and XNA for WP7? Me too! Michael Klucher has a post outlining the two: Silverlight and XNA Framework Game Development and Compatibility From SilverlightCream.com: Modularity in Silverlight Applications - An Issue With ModuleInitializeException Max Paulousky has a truly ugly error trace listed by way of not having a reference listed, and the obvious simple solution. Next time he'll talk about the difficult situations. Using SketchFlow to Prototype for Windows Phone Christian Schormann has a tutorial up on using Expression Blend to develop for WP7 ... who better than Christian for that task?? Silverlight TV 18: WCF RIA Services Validation John Papa held forth with Nikhil Kothari on WCF RIA Services and validation just prior to MIX10, and was posted yesterday. Building SL3 applications using OData client Library with Vs 2010 RC Phani Raj walks through building an OData consumer in SL3, the first problem you're going to hit, and the easy solution to it. Tip: When creating a DependencyProperty, follow the handy convention of "wrapper+register+static+virtual" David Anson has a couple more of his 'Tips' up... this first is about Dependency Properties again... having a good foundation for all your Dependency Properties is a great way to avoid problems. Tip: Do not assign DependencyProperty values in a constructor; it prevents users from overriding them In the next post, David Anson talks about not assigning Dependency Property values in a constructor and gives one of the two ways to get around doing so. Tip: Set DependencyProperty default values in a class's default style if it's more convenient In his latest post, David Anson gives the second way to avoid setting a Dependency Property value in the constructor. Silverlight 4 + RIA Services - Ready for Business: Search Engine Optimization (SEO) Brad Abrams Abrams adds SEO to the tutorial series he's doing. He begins with his PDC09 session material on the subject and then takes off on a great detailed tutorial all with source. Silverlight 4 + RIA Services - Ready for Business: Localizing Business Application Brad Abrams then discusses localization and Silverlight in another detailed tutorial with all code included. Silverlight Toolkit and the Windows Phone: WrapPanel, and a few others Jeff Wilcox has a few WP7 posts I'm going to push today. This first is from earlier this week and is about using the Toolkit in WP7 and better than that, he includes the bits you need if all you want is the WrapPanel Data binding user settings in Windows Phone applications In the next one from yesterday, Jeff Wilcox demonstrates saving some user info in Isolated Storage to improve the user experience, and shares all the necessary plumbing files, and other external links as well. Displaying 2D QR barcodes in Windows Phone applications In a post from today, Jeff Wilcox ported his Silverlight 2D QR Barcode app from last year into WP7 ... just very cool... get the source and display your Microsoft Tag. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone    MIX10

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  • SQL SERVER – Identity Fields – Contest Win Joes 2 Pros Combo (USD 198) – Day 2 of 5

    - by pinaldave
    August 2011 we ran a contest where every day we give away one book for an entire month. The contest had extreme success. Lots of people participated and lots of give away. I have received lots of questions if we are doing something similar this month. Absolutely, instead of running a contest a month long we are doing something more interesting. We are giving away USD 198 worth gift every day for this week. We are giving away Joes 2 Pros 5 Volumes (BOOK) SQL 2008 Development Certification Training Kit every day. One copy in India and One in USA. Total 2 of the giveaway (worth USD 198). All the gifts are sponsored from the Koenig Training Solution and Joes 2 Pros. The books are available here Amazon | Flipkart | Indiaplaza How to Win: Read the Question Read the Hints Answer the Quiz in Contact Form in following format Question Answer Name of the country (The contest is open for USA and India residents only) 2 Winners will be randomly selected announced on August 20th. Question of the Day: Which of the following statement is incorrect? a) Identity value can be negative. b) Identity value can have negative interval. c) Identity value can be of datatype VARCHAR d) Identity value can have increment interval larger than 1 Query Hints: BIG HINT POST A simple way to determine if a table contains an identity field is to use the SSMS Object Explorer Design Interface. Navigate to the table, then right-click it and choose Design from the pop-up window. When your design tab opens, select the first field in the table to view its list of properties in the lower pane of the tab (In this case the field is ProductID). Look to see if the Identity Specification property in the lower pane is set to either yes or no. SQL Server will allow you to utilize IDENTITY_INSERT with just one table at a time. After you’ve completed the needed work, it’s very important to reset the IDENTITY_INSERT back to OFF. Additional Hints: I have previously discussed various concepts from SQL Server Joes 2 Pros Volume 2. SQL Joes 2 Pros Development Series – Output Clause in Simple Examples SQL Joes 2 Pros Development Series – Ranking Functions – Advanced NTILE in Detail SQL Joes 2 Pros Development Series – Ranking Functions – RANK( ), DENSE_RANK( ), and ROW_NUMBER( ) SQL Joes 2 Pros Development Series – Advanced Aggregates with the Over Clause SQL Joes 2 Pros Development Series – Aggregates with the Over Clause SQL Joes 2 Pros Development Series – Overriding Identity Fields – Tricks and Tips of Identity Fields SQL Joes 2 Pros Development Series – Many to Many Relationships Next Step: Answer the Quiz in Contact Form in following format Question Answer Name of the country (The contest is open for USA and India) Bonus Winner Leave a comment with your favorite article from the “additional hints” section and you may be eligible for surprise gift. There is no country restriction for this Bonus Contest. Do mention why you liked it any particular blog post and I will announce the winner of the same along with the main contest. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • BizTalk 2009 - Architecture Decisions

    - by StuartBrierley
    In the first step towards implementing a BizTalk 2009 environment, from development through to live, I put forward a proposal that detailed the options available, as well as the costs and benefits associated with these options, to allow an informed discusion to take place with the business drivers and budget holders of the project.  This ultimately lead to a decision being made to implement an initial BizTalk Server 2009 environment using the Standard Edition of the product. It is my hope that in the long term, as projects require it and allow, we will be looking to implement my ideal recommendation of a multi-server enterprise level environment, but given the differences in cost and the likely initial work load for the environment this was not something that I could fully recommend at this time.  However, it must be noted that this decision was made in full awareness of the limits of the standard edition, and the business drivers of this project were made fully aware of the risks associated with running without the failover capabilities of the enterprise edition. When considering the creation of this new BizTalk Server 2009 environment, I have also recommended the creation of the following pre-production environments:   Usage Environment Development Development of solutions; Unit testing against technical specifications; Initial load testing; Testing of deployment packages;  Visual Studio; BizTalk; SQL; Client PCs/Laptops; Server environment similar to Live implementation; Test Testing of Solutions against business and technical requirements;  BizTalk; SQL; Server environment similar to Live implementation; Pseudo-Live As Live environment to allow testing against Live implementation; Acts as back-up hardware in case of failure of Live environment; BizTalk; SQL; Server environment identical to Live implementation; The creation of these differing environments allows for the separation of the various stages of the development cycle.  The development environment is for use when actively developing a solution, it is a potentially volatile environment whose state at any given time can not be guaranteed.  It allows developers to carry out initial tests in an environment that is similar to the live environment and also provides an area for the testing of deployment packages prior to any release to the test environment. The test environment is intended to be a semi-volatile environment that is similar to the live environment.  It will change periodically through the development of a solution (or solutions) but should be otherwise stable.  It allows for the continued testing of a solution against requirements without the worry that the environment is being actively changed by any ongoing development.  This separation of development and test is crucial in ensuring the quality and control of the tested solution. The pseudo-live environment should be considered to be an almost static environment.  It should mimic the live environment and can act as back up hardware in the case of live failure.  This environment acts as an area to allow for “as live” testing, where the performance and behaviour of the live solutions can be replicated.  There should be relatively few changes to this environment, with software releases limited to “release candidate” level releases prior to going live. Whereas the pseudo-live environment should always mimic the live environment, to save on costs the development and test servers could be implemented on lower specification hardware.  Consideration can also be given to the use of a virtual server environment to further reduce hardware costs in the development and test environments, indeed this virtual approach can also be extended to pseudo-live and live assuming the underlying technology is in place. Although there is no requirement for the development and test server environments to be identical to live, the overriding architecture implemented should be the same as in live and an understanding must be gained of the performance differences to be expected across the different environments.

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  • Hidden exceptions

    - by user12617285
    Occasionally you may find yourself in a Java application environment where exceptions in your code are being caught by the application framework and either silently swallowed or converted into a generic exception. Either way, the potentially useful details of your original exception are inaccessible. Wouldn't it be nice if there was a VM option that showed the stack trace for every exception thrown, whether or not it's caught? In fact, HotSpot includes such an option: -XX:+TraceExceptions. However, this option is only available in a debug build of HotSpot (search globals.hpp for TraceExceptions). And based on a quick skim of the HotSpot source code, this option only prints the exception class and message. A more useful capability would be to have the complete stack trace printed as well as the code location catching the exception. This is what the various TraceException* options in in Maxine do (and more). That said, there is a way to achieve a limited version of the same thing with a stock standard JVM. It involves the use of the -Xbootclasspath/p non-standard option. The trick is to modify the source of java.lang.Exception by inserting the following: private static final boolean logging = System.getProperty("TraceExceptions") != null; private void log() { if (logging && sun.misc.VM.isBooted()) { printStackTrace(); } } Then every constructor simply needs to be modified to call log() just before returning: public Exception(String message) { super(message); log(); } public Exception(String message, Throwable cause) { super(message, cause); log(); } // etc... You now need to compile the modified Exception.java source and prepend the resulting class to the boot class path as well as add -DTraceExceptions to your java command line. Here's a console session showing these steps: % mkdir boot % javac -d boot Exception.java % java -DTraceExceptions -Xbootclasspath/p:boot -cp com.oracle.max.vm/bin test.output.HelloWorld java.util.zip.ZipException: error in opening zip file at java.util.zip.ZipFile.open(Native Method) at java.util.zip.ZipFile.(ZipFile.java:127) at java.util.jar.JarFile.(JarFile.java:135) at java.util.jar.JarFile.(JarFile.java:72) at sun.misc.URLClassPath$JarLoader.getJarFile(URLClassPath.java:646) at sun.misc.URLClassPath$JarLoader.access$600(URLClassPath.java:540) at sun.misc.URLClassPath$JarLoader$1.run(URLClassPath.java:607) at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath$JarLoader.ensureOpen(URLClassPath.java:599) at sun.misc.URLClassPath$JarLoader.(URLClassPath.java:583) at sun.misc.URLClassPath$3.run(URLClassPath.java:333) at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath.getLoader(URLClassPath.java:322) at sun.misc.URLClassPath.getLoader(URLClassPath.java:299) at sun.misc.URLClassPath.getResource(URLClassPath.java:168) at java.net.URLClassLoader$1.run(URLClassLoader.java:194) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at sun.misc.Launcher$ExtClassLoader.findClass(Launcher.java:229) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at java.lang.ClassLoader.loadClass(ClassLoader.java:295) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) java.security.PrivilegedActionException at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath$JarLoader.ensureOpen(URLClassPath.java:599) at sun.misc.URLClassPath$JarLoader.(URLClassPath.java:583) at sun.misc.URLClassPath$3.run(URLClassPath.java:333) at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath.getLoader(URLClassPath.java:322) ... It's worth pointing out that this is not as useful as direct VM support for tracing exceptions. It has (at least) the following limitations: The trace is shown for every exception, whether it is thrown or not. It only applies to subclasses of java.lang.Exception as there appears to be bootstrap issues when the modification is applied to Throwable.java. It does not show you where the exception was caught. It involves overriding a class in rt.jar, something should never be done in a non-development environment.

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  • Getting input from keyboard

    - by SAMIR BHOGAYTA
    When you type on the keyboard the keystrokes go to a particular application, the active application. The active application receives the input from the keyboard. This means the application has input focus. There are two events for a key on a keyboard, when the key is pressed and when it is released. No it's not a single event as you might expect if you have no prior programming experience, in shooter games for example when you keep the forward key pressed (KeyDown) the player goes forward, and when it isn't pressed (KeyUp) the player stays put. The event that occurs when the key is pressed is called KeyPress. It occurs between KeyDown and KeyUp, and therefore acts similar to KeyDown. Similar to the way we handle OnPaint and other events we also handle the OnKeyDown event (because we want the event to occur when the key is pressed and not when it is released) by overriding it. Try the code below and test it. You will understand the role of each property. protected override void OnKeyDown(KeyEventArgs keyEvent) { // Gets the key code lblKeyCode.Text = "KeyCode: " + keyEvent.KeyCode.ToString(); // Gets the key data; recognizes combination of keys lblKeyData.Text = "KeyData: " + keyEvent.KeyData.ToString(); // Integer representation of KeyData lblKeyValue.Text = "KeyValue: " + keyEvent.KeyValue.ToString(); // Returns true if Alt is pressed lblAlt.Text = "Alt: " + keyEvent.Alt.ToString(); // Returns true if Ctrl is pressed lblCtrl.Text = "Ctrl: " + keyEvent.Control.ToString(); // Returns true if Shift is pressed lblShift.Text = "Shift: " + keyEvent.Shift.ToString(); } How do I find out when the user presses a specific key? As you probably imagine, this will be easily accomplished using 'if'. if (keyEvent.KeyCode == Keys.A) { MessageBox.Show("'A' was pressed."); } Probably most beginners would be tempted to do this: if (keyEvent.KeyCode == "A") .... which is definitely incorrect because we can't compare System.Windows.Forms.Keys to a string. Also note that in the example we are using 'keyEvent.KeyCode', that means that even if we have other shift keys pressed (Alt, Ctrl, Shift, Windows...) simultaneous with A, the if condition returns true because it doesn't recognize key combinations. If we want to ignore key combinations (Alt+A, Ctrl+Shift+A), etc. we need to use 'keyEvent.KeyData' of course: if (keyEvent.KeyData == Keys.A) { MessageBox.Show("'A', and only A, was pressed."); } When you right click on a file in Windows Explorer and you have the Shift key pressed you get the additional 'Open with...' item in the menu. This and many others are cases when you need to use the mouse button together with the keyboard. The following code will change the background color of the form only if the form is clicked while the Ctrl key on the keyboard is pressed. If the Ctrl key is unpressed and the form is clicked nothing happens. private void Form1_Click(object sender, System.EventArgs e) { Keys modKey = Control.ModifierKeys; if(modKey == Keys.Control) { this.BackColor = Color.Yellow; } } If you have further questions feel free to ask them and also check the following pages at MSDN: KeyUp Event KeyPress Event KeyDown Event

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  • Building ATLAS (and later Octave w/ ATLAS)

    - by David Parks
    I'm trying to set up ATLAS (so I can later compile octave with ATLAS support). If I'm correct, I still need to build this manually due to the environment specific optimizations. I do see a package for ATLAS, but it looks like it's using the cross platform generic build options (e.g. "it'll be slow"). So, running the configure script as described in the docs seems to go poorly. As a java developer I never do well at making heads or tails of errors in these build processes. Am I missing dependencies (if so is there any documentation on what I need)? allusers@vbubuntu:~/Downloads/atlas3.10.1/build_vbubuntu$ ../configure -b 64 -D c -DPentiumCPS=3000 --with-netlib-lapack-tarfile=/home/allusers/Downloads/lapack-3.5.0.tgz make: `xconfig' is up to date. ./xconfig -d s /home/allusers/Downloads/atlas3.10.1/build_vbubuntu/../ -d b /home/allusers/Downloads/atlas3.10.1/build_vbubuntu -b 64 -D c -DPentiumCPS=3000 -Si lapackref 1 OS configured as Linux (1) Assembly configured as GAS_x8664 (2) Vector ISA Extension configured as SSE3 (6,448) ERROR: enum fam=3, chip=2, mach=0 make[3]: *** [atlas_run] Error 44 make[2]: *** [IRunArchInfo_x86] Error 2 Architecture configured as Corei1 (25) ERROR: enum fam=3, chip=2, mach=0 make[3]: *** [atlas_run] Error 44 make[2]: *** [IRunArchInfo_x86] Error 2 Clock rate configured as 2350Mhz ERROR: enum fam=3, chip=2, mach=0 make[3]: *** [atlas_run] Error 44 make[2]: *** [IRunArchInfo_x86] Error 2 Maximum number of threads configured as 4 Parallel make command configured as '$(MAKE) -j 4' ERROR: enum fam=3, chip=2, mach=0 make[3]: *** [atlas_run] Error 44 make[2]: *** [IRunArchInfo_x86] Error 2 Cannot detect CPU throttling. rm -f config1.out make atlas_run atldir=/home/allusers/Downloads/atlas3.10.1/build_vbubuntu exe=xprobe_comp redir=config1.out \ args="-v 0 -o atlconf.txt -O 1 -A 25 -Si nof77 0 -V 448 -b 64 -d b /home/allusers/Downloads/atlas3.10.1/build_vbubuntu" make[1]: Entering directory `/home/allusers/Downloads/atlas3.10.1/build_vbubuntu' cd /home/allusers/Downloads/atlas3.10.1/build_vbubuntu ; ./xprobe_comp -v 0 -o atlconf.txt -O 1 -A 25 -Si nof77 0 -V 448 -b 64 -d b /home/allusers/Downloads/atlas3.10.1/build_vbubuntu > config1.out make[2]: gfortran: Command not found make[2]: *** [IRunF77Comp] Error 127 make[2]: g77: Command not found make[2]: *** [IRunF77Comp] Error 127 make[2]: f77: Command not found make[2]: *** [IRunF77Comp] Error 127 Unable to find usable compiler for F77; abortingMake sure compilers are in your path, and specify good compilers to configure (see INSTALL.txt or 'configure --help' for details)make[1]: *** [atlas_run] Error 8 make[1]: Leaving directory `/home/allusers/Downloads/atlas3.10.1/build_vbubuntu' make: *** [IRun_comp] Error 2 ERROR 512 IN SYSCMND: 'make IRun_comp args="-v 0 -o atlconf.txt -O 1 -A 25 -Si nof77 0 -V 448 -b 64"' mkdir src bin tune interfaces mkdir: cannot create directory ‘src’: File exists mkdir: cannot create directory ‘bin’: File exists mkdir: cannot create directory ‘tune’: File exists mkdir: cannot create directory ‘interfaces’: File exists make: *** [make_subdirs] Error 1 make -f Make.top startup make[1]: Entering directory `/home/allusers/Downloads/atlas3.10.1/build_vbubuntu' Make.top:1: Make.inc: No such file or directory Make.top:325: warning: overriding commands for target `/AtlasTest' Make.top:76: warning: ignoring old commands for target `/AtlasTest' make[1]: *** No rule to make target `Make.inc'. Stop. make[1]: Leaving directory `/home/allusers/Downloads/atlas3.10.1/build_vbubuntu' make: *** [startup] Error 2 mv: cannot move ‘lapack-3.5.0’ to ‘../reference/lapack-3.5.0’: Directory not empty mv: cannot stat ‘lib/Makefile’: No such file or directory ../configure: 450: ../configure: cannot create lib/Makefile: Directory nonexistent ../configure: 451: ../configure: cannot create lib/Makefile: Directory nonexistent ../configure: 452: ../configure: cannot create lib/Makefile: Directory nonexistent ../configure: 453: ../configure: cannot create lib/Makefile: Directory nonexistent ../configure: 509: ../configure: cannot create lib/Makefile: Directory nonexistent DONE configure

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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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  • How can I fix my keyboard layout?

    - by Scott Severance
    For a long time, I've had my keyboard configured to use the layout currently known as "English (international AltGr dead keys)." I like this layout because without any modifier keys, it's identical to the US English keyboard, but when I hold Right Alt I can get accented letters and other characters not available on a standard US English keyboard. In Oneiric, however, the layout is messed up. Right Alt+N produces "ñ" as expected. And another method works: Right Alt+`, E produces "è", also as expected. But there's no way to type "é", which is probably the accented letter I type the most. I expect Right Alt+A, E to do the trick. But instead of a dead key for the acute accent, it uses a method for combining characters to create the hybrid "´e". This hybrid looks like the proper "é" in some settings, but it isn't the same character and doesn't always work. (For example, in the text input box as I type this, it looks the same as the proper character, but when displayed on the site for all so see, it looks very wrong--at least on my machine.) Ditto for all other characters with an acute accent, though some are available directly as pre-composed characters: For example, Right Alt+I yields "í". How can I change the acute accent on the A key to a proper dead key? Perhaps the more general version of this is: How can I tweak my keyboard layout? Update I just tested this on my other machine, also running Oneiric, but upgraded from previous versions. I have no problems with the second machine. The problem machine was a fresh install of Oneiric, but I kept my old $HOME when I did the fresh install. Clarification Even if an answer doesn't address my specific examples, I would still accept it if it provided enough detail for me to find the layout and tweak it according to my needs. Major Update After working through the information gained through Jim C's and Chascon's helpful replies, I've learned something new: The problem isn't with the layout itself, but with the fact that the selected layout isn't being applied. When I look at the definition in /usr/share/X11/xkb/symbols/us of the layout I've been running for a long time, I found that the definition doesn't match what I get when I type. In addition, the keyboard layout dialog that's supposed to show the current layout looks different from the way the layout is defined in the file I mentioned, and matches what actually happens when I type. Following Jim C's suggestion, I created a new layout in /usr/share/X11/xkb/symbols/us containing some modifications to the layout I want. I can select my layout from the keyboard properties, and I can use in on the console following Chascon's post, but the layout I get when typing is unchanged. Apparently, there's a different layout defined somewhere that's overriding what I've set. Where is that layout hiding? This problem occurs in Unity (3D and 2D), but I was able to get the correct layout set in Xfce. In case it's relevant, this problem has occurred since I installed Oneiric fresh on this machine (though I preserved my $HOME). I don't recall whether this problem occurred before the reinstall. Also, in case it's relevant, I also run iBus so I can type Korean. I have a few difficulties with iBus, but I doubt they're related.

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  • Where should instantiated classes be stored?

    - by Eric C.
    I'm having a bit of a design dilemma here. I'm writing a library that consists of a bunch of template classes that are designed to be used as a base for creating content. For example: public class Template { public string Name {get; set;} public string Description {get; set;} public string Attribute1 {get; set;} public string Attribute2 {get; set;} public Template() { //constructor } public void DoSomething() { //does something } ... } The problem is, not only is the library providing the templates, it will also supply quite a few predefined templates which are instances of these template classes. The question is, where do I put these instances of the templates? The three solutions I've come up with so far are: 1) Provide serialized instances of the templates as files. On the one hand, this solution would keep the instances separated from the library itself, which is nice, but it would also potentially add complexity for the user. Even if we provided methods for loading/deserializing the files, they'd still have to deal with a bunch of files, and some kind of config file so the app knows where to look for those files. Plus, creating the template files would probably require a separate app, so if the user wanted to stick with the files method of storing templates, we'd have to provide some kind of app for creating the template files. Also, this requires external dependencies for testing the templates in the user's code. 2) Add readonly instances to the template class Example: public class Template { public string Name {get; set;} public string Description {get; set;} public string Attribute1 {get; set;} public string Attribute2 {get; set;} public Template PredefinedTemplate { get { Template templateInstance = new Template(); templateInstance.Name = "Some Name"; templateInstance.Description = "A description"; ... return templateInstance; } } public Template() { //constructor } public void DoSomething() { //does something } ... } This method would be convenient for users, as they would be able to access the predefined templates in code directly, and would be able to unit test code that used them. The drawback here is that the predefined templates pollute the Template type namespace with a bunch of extra stuff. I suppose I could put the predefined templates in a different namespace to get around this drawback. The only other problem with this approach is that I'd have to basically duplicate all the namespaces in the library in the predefined namespace (e.g. Templates.SubTemplates and Predefined.Templates.SubTemplates) which would be a pain, and would also make refactoring more difficult. 3) Make the templates abstract classes and make the predefined templates inherit from those classes. For example: public abstract class Template { public string Name {get; set;} public string Description {get; set;} public string Attribute1 {get; set;} public string Attribute2 {get; set;} public Template() { //constructor } public void DoSomething() { //does something } ... } and public class PredefinedTemplate : Template { public PredefinedTemplate() { this.Name = "Some Name"; this.Description = "A description"; this.Attribute1 = "Some Value"; ... } } This solution is pretty similar to #2, but it ends up creating a lot of classes that don't really do anything (none of our predefined templates are currently overriding behavior), and don't have any methods, so I'm not sure how good a practice this is. Has anyone else had any experience with something like this? Is there a best practice of some kind, or a different/better approach that I haven't thought of? I'm kind of banging my head against a wall trying to figure out the best way to go. Thanks!

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  • Multiple Zend application code organisation

    - by user966936
    For the past year I have been working on a series of applications all based on the Zend framework and centered on a complex business logic that all applications must have access to even if they don't use all (easier than having multiple library folders for each application as they are all linked together with a common center). Without going into much detail about what the project is specifically about, I am looking for some input (as I am working on the project alone) on how I have "grouped" my code. I have tried to split it all up in such a way that it removes dependencies as much as possible. I'm trying to keep it as decoupled as I logically can, so in 12 months time when my time is up anyone else coming in can have no problem extending on what I have produced. Example structure: applicationStorage\ (contains all applications and associated data) applicationStorage\Applications\ (contains the applications themselves) applicationStorage\Applications\external\ (application grouping folder) (contains all external customer access applications) applicationStorage\Applications\external\site\ (main external customer access application) applicationStorage\Applications\external\site\Modules\ applicationStorage\Applications\external\site\Config\ applicationStorage\Applications\external\site\Layouts\ applicationStorage\Applications\external\site\ZendExtended\ (contains extended Zend classes specific to this application example: ZendExtended_Controller_Action extends zend_controller_Action ) applicationStorage\Applications\external\mobile\ (mobile external customer access application different workflow limited capabilities compared to full site version) applicationStorage\Applications\internal\ (application grouping folder) (contains all internal company applications) applicationStorage\Applications\internal\site\ (main internal application) applicationStorage\Applications\internal\mobile\ (mobile access has different flow and limited abilities compared to main site version) applicationStorage\Tests\ (contains PHP unit tests) applicationStorage\Library\ applicationStorage\Library\Service\ (contains all business logic, services and servicelocator; these are completely decoupled from Zend framework and rely on models' interfaces) applicationStorage\Library\Zend\ (Zend framework) applicationStorage\Library\Models\ (doesn't know services but is linked to Zend framework for DB operations; contains model interfaces and model datamappers for all business objects; examples include Iorder/IorderMapper, Iworksheet/IWorksheetMapper, Icustomer/IcustomerMapper) (Note: the Modules, Config, Layouts and ZendExtended folders are duplicated in each application folder; but i have omitted them as they are not required for my purposes.) For the library this contains all "universal" code. The Zend framework is at the heart of all applications, but I wanted my business logic to be Zend-framework-independent. All model and mapper interfaces have no public references to Zend_Db but actually wrap around it in private. So my hope is that in the future I will be able to rewrite the mappers and dbtables (containing a Models_DbTable_Abstract that extends Zend_Db_Table_Abstract) in order to decouple my business logic from the Zend framework if I want to move my business logic (services) to a non-Zend framework environment (maybe some other PHP framework). Using a serviceLocator and registering the required services within the bootstrap of each application, I can use different versions of the same service depending on the request and which application is being accessed. Example: all external applications will have a service_auth_External implementing service_auth_Interface registered. Same with internal aplications with Service_Auth_Internal implementing service_auth_Interface Service_Locator::getService('Auth'). I'm concerned I may be missing some possible problems with this. One I'm half-thinking about is a config.ini file for all externals, then a separate application config.ini overriding or adding to the global external config.ini. If anyone has any suggestions I would be greatly appreciative. I have used contextswitching for AJAX functions within the individual applications, but there is a big chance both external and internal will get web services created for them. Again, these will be separated due to authorization and different available services. \applicationstorage\Applications\internal\webservice \applicationstorage\Applications\external\webservice

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  • Triple (3) Monitors under Linux

    - by widgisoft
    I have a 3 monitor setup (each 1680x1050) via an Nvidia NVS440 (2 GPUs, 2 outputs per GPU totalling 4 outputs); this works fine under Windows XP,7 but caused considerable headaches under Linux (Ubuntu 9.04). I had previously used an XFX 9600GT and the onboard XFX 9300GS to produce the same result but the card was noisy and power hungry and I was hoping that there was some magical switch in the NVS4400 that got rid of this annoying problem - turns out the NVS440 is just 2 cards on one physical PCB :-p (I searched the net high and low for people using this card under Linux but found nothing, if anything the card uses less power and is fan less so I was to benefit from it either way) Anyway, using either set up there were 5 solutions available: Have 3 separate X instances, all un joined Have 3 separate X instances, adjoined by Xinerama Have 2 separate X instances - One using twin-view, both adjoined by Xinerama Have 2 separate X instances - One using twin-view but no Xinerama Have a single Twin-view setup and leave the 3rd screen unplugged :-p The 4rd option, using 2 separate X instances and twinview (but no xinerama) was the best balance in terms of performance and usability but caused 2 really annoying issues You couldn't control (without altering the shortcuts) which screen an application opened onto - and once it was opened you couldn't move it to another screen without opening up terminal and forcing it to move Nvidia's overriding or falsifying of Xinerama breaks and the 2 screens joined by Twin view behave like a single huge screen causing popups to open in the middle of both screens and maximising of windows stretches to the width of the first 2 screens Firefox can only run one instance as the same user so having multiple firefox windows requires at least 2 users The second option "feels" like the right option, but OpenGL is basically disabled and playing any sort of game or even running anything graphical causes a huge performance drop and instability - even trying to run a basic emulator for gba or gens just causes the system to fall over. It works just enough to stare at your desktop and do nothing but as soon as you start doing some work - opening windows, dragging things around - running multiple copies of firefox it just really feels slow. The last open, only going dual screen works perfectly and everything performs as required, full GPU acceleration - two logical screen spaces - perfect, just make it work across GPUs like windows! :-p Anyway, I know RandR was supposed to pick up the slack when it would introduced GPU objects of sorts to allow multiple GPUs to be stitched together to create one huge desktop at a much deeper layer than Xinerama. I was wondering if this has now been fixed (I noticed X server 1.7 is out) and whether anyone has got it running successfully? Again, my requirements are: One huge desktop to drag any window across Maximising of windows to each screen (as XP does) Running fullscreen apps on the primary screen and disabling the mouse from moving onto the others or on all 3 stretched Finally as a side note; I am aware of the Matrox triple (and dual) head splitter but even the price they go for on eBay is more than I can afford atm, my argument: I shouldn't have to buy extra hardware to get something to work on Linux when it's something that's existed in the windows world for a long time (can you tell I don't get on with X :-p); If I had the cash I'd have bought the latest version of this box already (the new version finally supports large resolutions as the displays I have 1680x1050 each).

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  • Guarding against CSRF Attacks in ASP.NET MVC2

    - by srkirkland
    Alongside XSS (Cross Site Scripting) and SQL Injection, Cross-site Request Forgery (CSRF) attacks represent the three most common and dangerous vulnerabilities to common web applications today. CSRF attacks are probably the least well known but they are relatively easy to exploit and extremely and increasingly dangerous. For more information on CSRF attacks, see these posts by Phil Haack and Steve Sanderson. The recognized solution for preventing CSRF attacks is to put a user-specific token as a hidden field inside your forms, then check that the right value was submitted. It's best to use a random value which you’ve stored in the visitor’s Session collection or into a Cookie (so an attacker can't guess the value). ASP.NET MVC to the rescue ASP.NET MVC provides an HTMLHelper called AntiForgeryToken(). When you call <%= Html.AntiForgeryToken() %> in a form on your page you will get a hidden input and a Cookie with a random string assigned. Next, on your target Action you need to include [ValidateAntiForgeryToken], which handles the verification that the correct token was supplied. Good, but we can do better Using the AntiForgeryToken is actually quite an elegant solution, but adding [ValidateAntiForgeryToken] on all of your POST methods is not very DRY, and worse can be easily forgotten. Let's see if we can make this easier on the program but moving from an "Opt-In" model of protection to an "Opt-Out" model. Using AntiForgeryToken by default In order to mandate the use of the AntiForgeryToken, we're going to create an ActionFilterAttribute which will do the anti-forgery validation on every POST request. First, we need to create a way to Opt-Out of this behavior, so let's create a quick action filter called BypassAntiForgeryToken: [AttributeUsage(AttributeTargets.Method, AllowMultiple=false)] public class BypassAntiForgeryTokenAttribute : ActionFilterAttribute { } Now we are ready to implement the main action filter which will force anti forgery validation on all post actions within any class it is defined on: [AttributeUsage(AttributeTargets.Class, AllowMultiple = false)] public class UseAntiForgeryTokenOnPostByDefault : ActionFilterAttribute { public override void OnActionExecuting(ActionExecutingContext filterContext) { if (ShouldValidateAntiForgeryTokenManually(filterContext)) { var authorizationContext = new AuthorizationContext(filterContext.Controller.ControllerContext);   //Use the authorization of the anti forgery token, //which can't be inhereted from because it is sealed new ValidateAntiForgeryTokenAttribute().OnAuthorization(authorizationContext); }   base.OnActionExecuting(filterContext); }   /// <summary> /// We should validate the anti forgery token manually if the following criteria are met: /// 1. The http method must be POST /// 2. There is not an existing [ValidateAntiForgeryToken] attribute on the action /// 3. There is no [BypassAntiForgeryToken] attribute on the action /// </summary> private static bool ShouldValidateAntiForgeryTokenManually(ActionExecutingContext filterContext) { var httpMethod = filterContext.HttpContext.Request.HttpMethod;   //1. The http method must be POST if (httpMethod != "POST") return false;   // 2. There is not an existing anti forgery token attribute on the action var antiForgeryAttributes = filterContext.ActionDescriptor.GetCustomAttributes(typeof(ValidateAntiForgeryTokenAttribute), false);   if (antiForgeryAttributes.Length > 0) return false;   // 3. There is no [BypassAntiForgeryToken] attribute on the action var ignoreAntiForgeryAttributes = filterContext.ActionDescriptor.GetCustomAttributes(typeof(BypassAntiForgeryTokenAttribute), false);   if (ignoreAntiForgeryAttributes.Length > 0) return false;   return true; } } The code above is pretty straight forward -- first we check to make sure this is a POST request, then we make sure there aren't any overriding *AntiForgeryTokenAttributes on the action being executed. If we have a candidate then we call the ValidateAntiForgeryTokenAttribute class directly and execute OnAuthorization() on the current authorization context. Now on our base controller, you could use this new attribute to start protecting your site from CSRF vulnerabilities. [UseAntiForgeryTokenOnPostByDefault] public class ApplicationController : System.Web.Mvc.Controller { }   //Then for all of your controllers public class HomeController : ApplicationController {} What we accomplished If your base controller has the new default anti-forgery token attribute on it, when you don't use <%= Html.AntiForgeryToken() %> in a form (or of course when an attacker doesn't supply one), the POST action will throw the descriptive error message "A required anti-forgery token was not supplied or was invalid". Attack foiled! In summary, I think having an anti-CSRF policy by default is an effective way to protect your websites, and it turns out it is pretty easy to accomplish as well. Enjoy!

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  • ASP.NET MVC: Converting business objects to select list items

    - by DigiMortal
    Some of our business classes are used to fill dropdown boxes or select lists. And often you have some base class for all your business classes. In this posting I will show you how to use base business class to write extension method that converts collection of business objects to ASP.NET MVC select list items without writing a lot of code. BusinessBase, BaseEntity and other base classes I prefer to have some base class for all my business classes so I can easily use them regardless of their type in contexts I need. NB! Some guys say that it is good idea to have base class for all your business classes and they also suggest you to have mappings done same way in database. Other guys say that it is good to have base class but you don’t have to have one master table in database that contains identities of all your business objects. It is up to you how and what you prefer to do but whatever you do – think and analyze first, please. :) To keep things maximally simple I will use very primitive base class in this example. This class has only Id property and that’s it. public class BaseEntity {     public virtual long Id { get; set; } } Now we have Id in base class and we have one more question to solve – how to better visualize our business objects? To users ID is not enough, they want something more informative. We can define some abstract property that all classes must implement. But there is also another option we can use – overriding ToString() method in our business classes. public class Product : BaseEntity {     public virtual string SKU { get; set; }     public virtual string Name { get; set; }       public override string ToString()     {         if (string.IsNullOrEmpty(Name))             return base.ToString();           return Name;     } } Although you can add more functionality and properties to your base class we are at point where we have what we needed: identity and human readable presentation of business objects. Writing list items converter Now we can write method that creates list items for us. public static class BaseEntityExtensions {            public static IEnumerable<SelectListItem> ToSelectListItems<T>         (this IList<T> baseEntities) where T : BaseEntity     {         return ToSelectListItems((IEnumerator<BaseEntity>)                    baseEntities.GetEnumerator());     }       public static IEnumerable<SelectListItem> ToSelectListItems         (this IEnumerator<BaseEntity> baseEntities)     {         var items = new HashSet<SelectListItem>();           while (baseEntities.MoveNext())         {             var item = new SelectListItem();             var entity = baseEntities.Current;               item.Value = entity.Id.ToString();             item.Text = entity.ToString();               items.Add(item);         }           return items;     } } You can see here to overloads of same method. One works with List<T> and the other with IEnumerator<BaseEntity>. Although mostly my repositories return IList<T> when querying data there are always situations where I can use more abstract types and interfaces. Using extension methods in code In your code you can use ToSelectListItems() extension methods like shown on following code fragment. ... var model = new MyFormModel(); model.Statuses = _myRepository.ListStatuses().ToSelectListItems(); ... You can call this method on all your business classes that extend your base entity. Wanna have some fun with this code? Write overload for extension method that accepts selected item ID.

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  • using Unity Android In a sub view and add actionbar and style

    - by aeroxr1
    I exported a simple animation from Unity3D (version 4.5) in android project. With eclipse I modified the manifest and added another activity. In this activity I put a button that it makes start the animation,and this is the result. The action bar appear in the main activity but it doesn't in the unity's activity :( How can I add the action bar and the style of the first activity to unity's animation activity ? This is the unity's activity's code : package com.rabidgremlin.tut.redcube; import android.app.NativeActivity; import android.content.res.Configuration; import android.graphics.PixelFormat; import android.os.Bundle; import android.view.KeyEvent; import android.view.MotionEvent; import android.view.View; import android.view.ViewGroup; import android.view.Window; import android.view.WindowManager; import com.unity3d.player.UnityPlayer; public class UnityPlayerNativeActivity extends NativeActivity { protected UnityPlayer mUnityPlayer; // don't change the name of this variable; referenced from native code // Setup activity layout @Override protected void onCreate (Bundle savedInstanceState) { //requestWindowFeature(Window.FEATURE_NO_TITLE); super.onCreate(savedInstanceState); getWindow().takeSurface(null); //setTheme(android.R.style.Theme_NoTitleBar_Fullscreen); getWindow().setFormat(PixelFormat.RGB_565); mUnityPlayer = new UnityPlayer(this); /*if (mUnityPlayer.getSettings ().getBoolean ("hide_status_bar", true)) getWindow ().setFlags (WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); */ setContentView(mUnityPlayer); mUnityPlayer.requestFocus(); } // Quit Unity @Override protected void onDestroy () { mUnityPlayer.quit(); super.onDestroy(); } // Pause Unity @Override protected void onPause() { super.onPause(); mUnityPlayer.pause(); } // eliminiamo questa onResume() e proviamo a modificare la onResume() // Resume Unity @Override protected void onResume() { super.onResume(); mUnityPlayer.resume(); } // inseriamo qualche modifica qui // This ensures the layout will be correct. @Override public void onConfigurationChanged(Configuration newConfig) { super.onConfigurationChanged(newConfig); mUnityPlayer.configurationChanged(newConfig); } // Notify Unity of the focus change. @Override public void onWindowFocusChanged(boolean hasFocus) { super.onWindowFocusChanged(hasFocus); mUnityPlayer.windowFocusChanged(hasFocus); } // For some reason the multiple keyevent type is not supported by the ndk. // Force event injection by overriding dispatchKeyEvent(). @Override public boolean dispatchKeyEvent(KeyEvent event) { if (event.getAction() == KeyEvent.ACTION_MULTIPLE) return mUnityPlayer.injectEvent(event); return super.dispatchKeyEvent(event); } // Pass any events not handled by (unfocused) views straight to UnityPlayer @Override public boolean onKeyUp(int keyCode, KeyEvent event) { return mUnityPlayer.injectEvent(event); } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { return mUnityPlayer.injectEvent(event); } @Override public boolean onTouchEvent(MotionEvent event) { return mUnityPlayer.injectEvent(event); } /*API12*/ public boolean onGenericMotionEvent(MotionEvent event) { return mUnityPlayer.injectEvent(event); } } And this is the AndroidManifest.xml android:versionCode="1" android:versionName="1.0" > <!-- android:theme="@android:style/Theme.NoTitleBar"--> <supports-screens android:anyDensity="true" android:largeScreens="true" android:normalScreens="true" android:smallScreens="true" android:xlargeScreens="true" /> <application android:icon="@drawable/app_icon" android:label="@string/app_name" android:theme="@android:style/Theme.Holo.Light" > <activity android:name="com.rabidgremlin.tut.redcube.UnityPlayerNativeActivity" android:configChanges="mcc|mnc|locale|touchscreen|keyboard|keyboardHidden|navigation|orientation|screenLayout|uiMode|screenSize|smallestScreenSize|fontScale" android:label="@string/app_name" android:screenOrientation="portrait" > <!--android:launchMode="singleTask"--> <meta-data android:name="unityplayer.UnityActivity" android:value="true" /> <meta-data android:name="unityplayer.ForwardNativeEventsToDalvik" android:value="false" /> </activity> <activity android:name="com.rabidgremlin.tut.redcube.MainActivity" android:label="@string/title_activity_main" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> <uses-sdk android:minSdkVersion="17" android:targetSdkVersion="19" /> <uses-feature android:glEsVersion="0x00020000" /> </manifest>

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  • Implementing an Interceptor Using NHibernate’s Built In Dynamic Proxy Generator

    - by Ricardo Peres
    NHibernate 3.2 came with an included proxy generator, which means there is no longer the need – or the possibility, for that matter – to choose Castle DynamicProxy, LinFu or Spring. This is actually a good thing, because it means one less assembly to deploy. Apparently, this generator was based, at least partially, on LinFu. As there are not many tutorials out there demonstrating it’s usage, here’s one, for demonstrating one of the most requested features: implementing INotifyPropertyChanged. This interceptor, of course, will still feature all of NHibernate’s functionalities that you are used to, such as lazy loading, and such. We will start by implementing an NHibernate interceptor, by inheriting from the base class NHibernate.EmptyInterceptor. This class does not do anything by itself, but it allows us to plug in behavior by overriding some of its methods, in this case, Instantiate: 1: public class NotifyPropertyChangedInterceptor : EmptyInterceptor 2: { 3: private ISession session = null; 4:  5: private static readonly ProxyFactory factory = new ProxyFactory(); 6:  7: public override void SetSession(ISession session) 8: { 9: this.session = session; 10: base.SetSession(session); 11: } 12:  13: public override Object Instantiate(String clazz, EntityMode entityMode, Object id) 14: { 15: Type entityType = Type.GetType(clazz); 16: IProxy proxy = factory.CreateProxy(entityType, new _NotifyPropertyChangedInterceptor(), typeof(INotifyPropertyChanged)) as IProxy; 17: 18: _NotifyPropertyChangedInterceptor interceptor = proxy.Interceptor as _NotifyPropertyChangedInterceptor; 19: interceptor.Proxy = this.session.SessionFactory.GetClassMetadata(entityType).Instantiate(id, entityMode); 20:  21: this.session.SessionFactory.GetClassMetadata(entityType).SetIdentifier(proxy, id, entityMode); 22:  23: return (proxy); 24: } 25: } Then we need a class that implements the NHibernate dynamic proxy behavior, let’s place it inside our interceptor, because it will only need to be used there: 1: class _NotifyPropertyChangedInterceptor : NHibernate.Proxy.DynamicProxy.IInterceptor 2: { 3: private PropertyChangedEventHandler changed = delegate { }; 4:  5: public Object Proxy 6: { 7: get; 8: set;} 9:  10: #region IInterceptor Members 11:  12: public Object Intercept(InvocationInfo info) 13: { 14: Boolean isSetter = info.TargetMethod.Name.StartsWith("set_") == true; 15: Object result = null; 16:  17: if (info.TargetMethod.Name == "add_PropertyChanged") 18: { 19: PropertyChangedEventHandler propertyChangedEventHandler = info.Arguments[0] as PropertyChangedEventHandler; 20: this.changed += propertyChangedEventHandler; 21: } 22: else if (info.TargetMethod.Name == "remove_PropertyChanged") 23: { 24: PropertyChangedEventHandler propertyChangedEventHandler = info.Arguments[0] as PropertyChangedEventHandler; 25: this.changed -= propertyChangedEventHandler; 26: } 27: else 28: { 29: result = info.TargetMethod.Invoke(this.Proxy, info.Arguments); 30: } 31:  32: if (isSetter == true) 33: { 34: String propertyName = info.TargetMethod.Name.Substring("set_".Length); 35: this.changed(this.Proxy, new PropertyChangedEventArgs(propertyName)); 36: } 37:  38: return (result); 39: } 40:  41: #endregion 42: } What this does for every interceptable method (those who are either virtual or from the INotifyPropertyChanged) is: For methods that came from the INotifyPropertyChanged interface, add_PropertyChanged and remove_PropertyChanged (yes, events are methods ), we add an implementation that adds or removes the event handlers to the delegate which we declared as changed; For all the others, we direct them to the place where they are actually implemented, which is the Proxy field; If the call is setting a property, it fires afterwards the PropertyChanged event. In order to use this, we need to add the interceptor to the Configuration before building the ISessionFactory: 1: using (ISessionFactory factory = cfg.SetInterceptor(new NotifyPropertyChangedInterceptor()).BuildSessionFactory()) 2: { 3: using (ISession session = factory.OpenSession()) 4: using (ITransaction tx = session.BeginTransaction()) 5: { 6: Customer customer = session.Get<Customer>(100); //some id 7: INotifyPropertyChanged inpc = customer as INotifyPropertyChanged; 8: inpc.PropertyChanged += delegate(Object sender, PropertyChangedEventArgs e) 9: { 10: //fired when a property changes 11: }; 12: customer.Address = "some other address"; //will raise PropertyChanged 13: customer.RecentOrders.ToList(); //will trigger the lazy loading 14: } 15: } Any problems, questions, do drop me a line!

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  • A Custom View Engine with Dynamic View Location

    - by imran_ku07
        Introduction:          One of the nice feature of ASP.NET MVC framework is its pluggability. This means you can completely replace the default view engine(s) with a custom one. One of the reason for using a custom view engine is to change the default views location and sometimes you need to change the views location at run-time. For doing this, you can extend the default view engine(s) and then change the default views location variables at run-time.  But, you cannot directly change the default views location variables at run-time because they are static and shared among all requests. In this article, I will show you how you can dynamically change the views location without changing the default views location variables at run-time.       Description:           Let's say you need to synchronize the views location with controller name and controller namespace. So, instead of searching to the default views location(Views/ControllerName/ViewName) to locate views, this(these) custom view engine(s) will search in the Views/ControllerNameSpace/ControllerName/ViewName folder to locate views.           First of all create a sample ASP.NET MVC 3 application and then add these custom view engines to your application,   public class MyRazorViewEngine : RazorViewEngine { public MyRazorViewEngine() : base() { AreaViewLocationFormats = new[] { "~/Areas/{2}/Views/%1/{1}/{0}.cshtml", "~/Areas/{2}/Views/%1/{1}/{0}.vbhtml", "~/Areas/{2}/Views/%1/Shared/{0}.cshtml", "~/Areas/{2}/Views/%1/Shared/{0}.vbhtml" }; AreaMasterLocationFormats = new[] { "~/Areas/{2}/Views/%1/{1}/{0}.cshtml", "~/Areas/{2}/Views/%1/{1}/{0}.vbhtml", "~/Areas/{2}/Views/%1/Shared/{0}.cshtml", "~/Areas/{2}/Views/%1/Shared/{0}.vbhtml" }; AreaPartialViewLocationFormats = new[] { "~/Areas/{2}/Views/%1/{1}/{0}.cshtml", "~/Areas/{2}/Views/%1/{1}/{0}.vbhtml", "~/Areas/{2}/Views/%1/Shared/{0}.cshtml", "~/Areas/{2}/Views/%1/Shared/{0}.vbhtml" }; ViewLocationFormats = new[] { "~/Views/%1/{1}/{0}.cshtml", "~/Views/%1/{1}/{0}.vbhtml", "~/Views/%1/Shared/{0}.cshtml", "~/Views/%1/Shared/{0}.vbhtml" }; MasterLocationFormats = new[] { "~/Views/%1/{1}/{0}.cshtml", "~/Views/%1/{1}/{0}.vbhtml", "~/Views/%1/Shared/{0}.cshtml", "~/Views/%1/Shared/{0}.vbhtml" }; PartialViewLocationFormats = new[] { "~/Views/%1/{1}/{0}.cshtml", "~/Views/%1/{1}/{0}.vbhtml", "~/Views/%1/Shared/{0}.cshtml", "~/Views/%1/Shared/{0}.vbhtml" }; } protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath) { var nameSpace = controllerContext.Controller.GetType().Namespace; return base.CreatePartialView(controllerContext, partialPath.Replace("%1", nameSpace)); } protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath) { var nameSpace = controllerContext.Controller.GetType().Namespace; return base.CreateView(controllerContext, viewPath.Replace("%1", nameSpace), masterPath.Replace("%1", nameSpace)); } protected override bool FileExists(ControllerContext controllerContext, string virtualPath) { var nameSpace = controllerContext.Controller.GetType().Namespace; return base.FileExists(controllerContext, virtualPath.Replace("%1", nameSpace)); } } public class MyWebFormViewEngine : WebFormViewEngine { public MyWebFormViewEngine() : base() { MasterLocationFormats = new[] { "~/Views/%1/{1}/{0}.master", "~/Views/%1/Shared/{0}.master" }; AreaMasterLocationFormats = new[] { "~/Areas/{2}/Views/%1/{1}/{0}.master", "~/Areas/{2}/Views/%1/Shared/{0}.master", }; ViewLocationFormats = new[] { "~/Views/%1/{1}/{0}.aspx", "~/Views/%1/{1}/{0}.ascx", "~/Views/%1/Shared/{0}.aspx", "~/Views/%1/Shared/{0}.ascx" }; AreaViewLocationFormats = new[] { "~/Areas/{2}/Views/%1/{1}/{0}.aspx", "~/Areas/{2}/Views/%1/{1}/{0}.ascx", "~/Areas/{2}/Views/%1/Shared/{0}.aspx", "~/Areas/{2}/Views/%1/Shared/{0}.ascx", }; PartialViewLocationFormats = ViewLocationFormats; AreaPartialViewLocationFormats = AreaViewLocationFormats; } protected override IView CreatePartialView(ControllerContext controllerContext, string partialPath) { var nameSpace = controllerContext.Controller.GetType().Namespace; return base.CreatePartialView(controllerContext, partialPath.Replace("%1", nameSpace)); } protected override IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath) { var nameSpace = controllerContext.Controller.GetType().Namespace; return base.CreateView(controllerContext, viewPath.Replace("%1", nameSpace), masterPath.Replace("%1", nameSpace)); } protected override bool FileExists(ControllerContext controllerContext, string virtualPath) { var nameSpace = controllerContext.Controller.GetType().Namespace; return base.FileExists(controllerContext, virtualPath.Replace("%1", nameSpace)); } }             Here, I am extending the RazorViewEngine and WebFormViewEngine class and then appending /%1 in each views location variable, so that we can replace /%1 at run-time. I am also overriding the FileExists, CreateView and CreatePartialView methods. In each of these method implementation, I am replacing /%1 with controller namespace. Now, just register these view engines in Application_Start method in Global.asax.cs file,   protected void Application_Start() { ViewEngines.Engines.Clear(); ViewEngines.Engines.Add(new MyRazorViewEngine()); ViewEngines.Engines.Add(new MyWebFormViewEngine()); ................................................ ................................................ }             Now just create a controller and put this controller's view inside Views/ControllerNameSpace/ControllerName folder and then run this application. You will find that everything works just fine.       Summary:          ASP.NET MVC uses convention over configuration to locate views. For many applications this convention to locate views is acceptable. But sometimes you may need to locate views at run-time. In this article, I showed you how you can dynamically locate your views by using a custom view engine. I am also attaching a sample application. Hopefully you will enjoy this article too. SyntaxHighlighter.all()  

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  • Breaking through the class sealing

    - by Jason Crease
    Do you understand 'sealing' in C#?  Somewhat?  Anyway, here's the lowdown. I've done this article from a C# perspective, but I've occasionally referenced .NET when appropriate. What is sealing a class? By sealing a class in C#, you ensure that you ensure that no class can be derived from that class.  You do this by simply adding the word 'sealed' to a class definition: public sealed class Dog {} Now writing something like " public sealed class Hamster: Dog {} " you'll get a compile error like this: 'Hamster: cannot derive from sealed type 'Dog' If you look in an IL disassembler, you'll see a definition like this: .class public auto ansi sealed beforefieldinit Dog extends [mscorlib]System.Object Note the addition of the word 'sealed'. What about sealing methods? You can also seal overriding methods.  By adding the word 'sealed', you ensure that the method cannot be overridden in a derived class.  Consider the following code: public class Dog : Mammal { public sealed override void Go() { } } public class Mammal { public virtual void Go() { } } In this code, the method 'Go' in Dog is sealed.  It cannot be overridden in a subclass.  Writing this would cause a compile error: public class Dachshund : Dog { public override void Go() { } } However, we can 'new' a method with the same name.  This is essentially a new method; distinct from the 'Go' in the subclass: public class Terrier : Dog { public new void Go() { } } Sealing properties? You can also seal seal properties.  You add 'sealed' to the property definition, like so: public sealed override string Name {     get { return m_Name; }     set { m_Name = value; } } In C#, you can only seal a property, not the underlying setters/getters.  This is because C# offers no override syntax for setters or getters.  However, in underlying IL you seal the setter and getter methods individually - a property is just metadata. Why bother sealing? There are a few traditional reasons to seal: Invariance. Other people may want to derive from your class, even though your implementation may make successful derivation near-impossible.  There may be twisted, hacky logic that could never be second-guessed by another developer.  By sealing your class, you're protecting them from wasting their time.  The CLR team has sealed most of the framework classes, and I assume they did this for this reason. Security.  By deriving from your type, an attacker may gain access to functionality that enables him to hack your system.  I consider this a very weak security precaution. Speed.  If a class is sealed, then .NET doesn't need to consult the virtual-function-call table to find the actual type, since it knows that no derived type can exist.  Therefore, it could emit a 'call' instead of 'callvirt' or at least optimise the machine code, thus producing a performance benefit.  But I've done trials, and have been unable to demonstrate this If you have an example, please share! All in all, I'm not convinced that sealing is interesting or important.  Anyway, moving-on... What is automatically sealed? Value types and structs.  If they were not always sealed, all sorts of things would go wrong.  For instance, structs are laid-out inline within a class.  But what if you assigned a substruct to a struct field of that class?  There may be too many fields to fit. Static classes.  Static classes exist in C# but not .NET.  The C# compiler compiles a static class into an 'abstract sealed' class.  So static classes are already sealed in C#. Enumerations.  The CLR does not track the types of enumerations - it treats them as simple value types.  Hence, polymorphism would not work. What cannot be sealed? Interfaces.  Interfaces exist to be implemented, so sealing to prevent implementation is dumb.  But what if you could prevent interfaces from being extended (i.e. ban declarations like "public interface IMyInterface : ISealedInterface")?  There is no good reason to seal an interface like this.  Sealing finalizes behaviour, but interfaces have no intrinsic behaviour to finalize Abstract classes.  In IL you can create an abstract sealed class.  But C# syntax for this already exists - declaring a class as a 'static', so it forces you to declare it as such. Non-override methods.  If a method isn't declared as override it cannot be overridden, so sealing would make no difference.  Note this is stated from a C# perspective - the words are opposite in IL.  In IL, you have four choices in total: no declaration (which actually seals the method), 'virtual' (called 'override' in C#), 'sealed virtual' ('sealed override' in C#) and 'newslot virtual' ('new virtual' or 'virtual' in C#, depending on whether the method already exists in a base class). Methods that implement interface methods.  Methods that implement an interface method must be virtual, so cannot be sealed. Fields.  A field cannot be overridden, only hidden (using the 'new' keyword in C#), so sealing would make no sense.

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  • Clean way to use mutable implementation of Immutable interfaces for encapsulation

    - by dsollen
    My code is working on some compost relationship which creates a tree structure, class A has many children of type B, which has many children of type C etc. The lowest level class, call it bar, also points to a connected bar class. This effectively makes nearly every object in my domain inter-connected. Immutable objects would be problematic due to the expense of rebuilding almost all of my domain to make a single change to one class. I chose to go with an interface approach. Every object has an Immutable interface which only publishes the getter methods. I have controller objects which constructs the domain objects and thus has reference to the full objects, thus capable of calling the setter methods; but only ever publishes the immutable interface. Any change requested will go through the controller. So something like this: public interface ImmutableFoo{ public Bar getBar(); public Location getLocation(); } public class Foo implements ImmutableFoo{ private Bar bar; private Location location; @Override public Bar getBar(){ return Bar; } public void setBar(Bar bar){ this.bar=bar; } @Override public Location getLocation(){ return Location; } } public class Controller{ Private Map<Location, Foo> fooMap; public ImmutableFoo addBar(Bar bar){ Foo foo=fooMap.get(bar.getLocation()); if(foo!=null) foo.addBar(bar); return foo; } } I felt the basic approach seems sensible, however, when I speak to others they always seem to have trouble envisioning what I'm describing, which leaves me concerned that I may have a larger design issue then I'm aware of. Is it problematic to have domain objects so tightly coupled, or to use the quasi-mutable approach to modifying them? Assuming that the design approach itself isn't inherently flawed the particular discussion which left me wondering about my approach had to do with the presence of business logic in the domain objects. Currently I have my setter methods in the mutable objects do error checking and all other logic required to verify and make a change to the object. It was suggested that this should be pulled out into a service class, which applies all the business logic, to simplify my domain objects. I understand the advantage in mocking/testing and general separation of logic into two classes. However, with a service method/object It seems I loose some of the advantage of polymorphism, I can't override a base class to add in new error checking or business logic. It seems, if my polymorphic classes were complicated enough, I would end up with a service method that has to check a dozen flags to decide what error checking and business logic applies. So, for example, if I wanted to have a childFoo which also had a size field which should be compared to bar before adding par my current approach would look something like this. public class Foo implements ImmutableFoo{ public void addBar(Bar bar){ if(!getLocation().equals(bar.getLocation()) throw new LocationException(); this.bar=bar; } } public interface ImmutableChildFoo extends ImmutableFoo{ public int getSize(); } public ChildFoo extends Foo implements ImmutableChildFoo{ private int size; @Override public int getSize(){ return size; } @Override public void addBar(Bar bar){ if(getSize()<bar.getSize()){ throw new LocationException(); super.addBar(bar); } My colleague was suggesting instead having a service object that looks something like this (over simplified, the 'service' object would likely be more complex). public interface ImmutableFoo{ ///original interface, presumably used in other methods public Location getLocation(); public boolean isChildFoo(); } public interface ImmutableSizedFoo implements ImmutableFoo{ public int getSize(); } public class Foo implements ImmutableSizedFoo{ public Bar bar; @Override public void addBar(Bar bar){ this.bar=bar; } @Override public int getSize(){ //default size if no size is known return 0; } @Override public boolean isChildFoo return false; } } public ChildFoo extends Foo{ private int size; @Override public int getSize(){ return size; } @Override public boolean isChildFoo(); return true; } } public class Controller{ Private Map<Location, Foo> fooMap; public ImmutableSizedFoo addBar(Bar bar){ Foo foo=fooMap.get(bar.getLocation()); service.addBarToFoo(foo, bar); returned foo; } public class Service{ public static void addBarToFoo(Foo foo, Bar bar){ if(foo==null) return; if(!foo.getLocation().equals(bar.getLocation())) throw new LocationException(); if(foo.isChildFoo() && foo.getSize()<bar.getSize()) throw new LocationException(); foo.setBar(bar); } } } Is the recommended approach of using services and inversion of control inherently superior, or superior in certain cases, to overriding methods directly? If so is there a good way to go with the service approach while not loosing the power of polymorphism to override some of the behavior?

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  • yield – Just yet another sexy c# keyword?

    - by George Mamaladze
    yield (see NSDN c# reference) operator came I guess with .NET 2.0 and I my feeling is that it’s not as wide used as it could (or should) be.   I am not going to talk here about necessarity and advantages of using iterator pattern when accessing custom sequences (just google it).   Let’s look at it from the clean code point of view. Let's see if it really helps us to keep our code understandable, reusable and testable.   Let’s say we want to iterate a tree and do something with it’s nodes, for instance calculate a sum of their values. So the most elegant way would be to build a recursive method performing a classic depth traversal returning the sum.           private int CalculateTreeSum(Node top)         {             int sumOfChildNodes = 0;             foreach (Node childNode in top.ChildNodes)             {                 sumOfChildNodes += CalculateTreeSum(childNode);             }             return top.Value + sumOfChildNodes;         }     “Do One Thing” Nevertheless it violates one of the most important rules “Do One Thing”. Our  method CalculateTreeSum does two things at the same time. It travels inside the tree and performs some computation – in this case calculates sum. Doing two things in one method is definitely a bad thing because of several reasons: ·          Understandability: Readability / refactoring ·          Reuseability: when overriding - no chance to override computation without copying iteration code and vice versa. ·          Testability: you are not able to test computation without constructing the tree and you are not able to test correctness of tree iteration.   I want to spend some more words on this last issue. How do you test the method CalculateTreeSum when it contains two in one: computation & iteration? The only chance is to construct a test tree and assert the result of the method call, in our case the sum against our expectation. And if the test fails you do not know wether was the computation algorithm wrong or was that the iteration? At the end to top it all off I tell you: according to Murphy’s Law the iteration will have a bug as well as the calculation. Both bugs in a combination will cause the sum to be accidentally exactly the same you expect and the test will PASS. J   Ok let’s use yield! That’s why it is generally a very good idea not to mix but isolate “things”. Ok let’s use yield!           private int CalculateTreeSumClean(Node top)         {             IEnumerable<Node> treeNodes = GetTreeNodes(top);             return CalculateSum(treeNodes);         }             private int CalculateSum(IEnumerable<Node> nodes)         {             int sumOfNodes = 0;             foreach (Node node in nodes)             {                 sumOfNodes += node.Value;             }             return sumOfNodes;         }           private IEnumerable<Node> GetTreeNodes(Node top)         {             yield return top;             foreach (Node childNode in top.ChildNodes)             {                 foreach (Node currentNode in GetTreeNodes(childNode))                 {                     yield return currentNode;                 }             }         }   Two methods does not know anything about each other. One contains calculation logic another jut the iteration logic. You can relpace the tree iteration algorithm from depth traversal to breath trevaersal or use stack or visitor pattern instead of recursion. This will not influence your calculation logic. And vice versa you can relace the sum with product or do whatever you want with node values, the calculateion algorithm is not aware of beeng working on some tree or graph.  How about not using yield? Now let’s ask the question – what if we do not have yield operator? The brief look at the generated code gives us an answer. The compiler generates a 150 lines long class to implement the iteration logic.       [CompilerGenerated]     private sealed class <GetTreeNodes>d__0 : IEnumerable<Node>, IEnumerable, IEnumerator<Node>, IEnumerator, IDisposable     {         ...        150 Lines of generated code        ...     }   Often we compromise code readability, cleanness, testability, etc. – to reduce number of classes, code lines, keystrokes and mouse clicks. This is the human nature - we are lazy. Knowing and using such a sexy construct like yield, allows us to be lazy, write very few lines of code and at the same time stay clean and do one thing in a method. That's why I generally welcome using staff like that.   Note: The above used recursive depth traversal algorithm is possibly the compact one but not the best one from the performance and memory utilization point of view. It was taken to emphasize on other primary aspects of this post.

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  • How to handle updated configuration when it's already been cloned for editing

    - by alexrussell
    Really sorry about the title that probably doesn't make much sense. Hopefully I can explain myself better here as it's something that's kinda bugged me for ages, and is now becoming a pressing concern as I write a bit of software with configuration. Most software comes with default configuration options stored in the app itself, and then there's a configuration file (let's say) that a user can edit. Once created/edited for the first time, subsequent updates to the application can not (easily) modify this configuration file for fear of clobbering the user's own changes to the default configuration. So my question is, if my application adds a new configurable parameter, what's the best way to aid discoverability of the setting and allow the user (developer) to override it as nicely as possible given the following constraints: I actually don't have a canonical default config in the application per se, it's more of a 'cascading filesystem'-like affair - the config template is stored in default/config.json and when the user wishes to edit the configuration, it's copied to user/config.json. If a user config is found it is used - there is no automatic overriding of a subset of keys, the whole new file is used and that's that. If there's no user config the default config is used. When a user wishes to edit the config they run a command to 'generate' it for them (which simply copies the config.json file from the default to the user directory). There is no UI for the configuration options as it's not appropriate to the userbase (think of my software as a library or something, the users are developers, the config is done in the user/config.json file). Due to my software being library-like there's no simple way to, on updating of the software, run some tasks automatically (so any ideas of look at the current config, compare to template config, add ing missing keys) aren't appropriate. The only solution I can think of right now is to say "there's a new config setting X" in release notes, but this doesn't seem ideal to me. If you want any more information let me know. The above specifics are not actually 100% true to my situation, but they represent the problem equally well with lower complexity. If you do want specifics, however, I can explain the exact setup. Further clarification of the type of configuration I mean: think of the Atom code editor. There appears to be a default 'template' config file somewhere, but as soon as a configuration option is edited ~/.atom/config.cson is generated and the setting goes in there. From now on is Atom is updated and gets a new configuration key, this file cannot be overwritten by Atom without a lot of effort to ensure that the addition/modification of the key does not clobber. In Atom's case, because there is a GUI for editing settings, they can get away with just adding the UI for the new setting into the UI to aid 'discoverability' of the new setting. I don't have that luxury. Clarification of my constraints and what I'm actually looking for: The software I'm writing is actually a package for a larger system. This larger system is what provides the configuration, and the way it works is kinda fixed - I just do a config('some.key') kinda call and it knows to look to see if the user has a config clone and if so use it, otherwise use the default config which is part of my package. Now, while I could make my application edit the user's configuration files (there is a convention about where they're stored), it's generally not done, so I'd like to live with the constraints of the system I'm using if possible. And it's not just about discoverability either, one large concern is that the addition of a configuration key won't actually work as soon as the user has their own copy of the original template. Adding the key to the template won't make a difference as that file is never read. As such, I think this is actually quite a big flaw in the design of the configuration cascading system and thus needs to be taken up with my upstream. So, thinking about it, based on my constraints, I don't think there's going to be a good solution save for either editing the user's configuration or using a new config file every time there are updates to the default configuration. Even the release notes idea from above isn't doable as, if the user does not follow the advice, suddenly I have a config key with no value (user-defined or default). So the new question is this: what is the general way to solve the problem of having a default configuration in template config files and allowing a user to make user-specific version of these in order to override the defaults? A per-key cascade (rather than per-file cascade) where the user only specifies their overrides? In this case, what happens if a configuration value is an array - do we replace or append to the default (or, more realistically, how does the user specify whether they wish to replace or append to)? It seems like configuration is kinda hard, so how is it solved in the wild?

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  • How to override C# DateTime serialization with class auto-generated from wsdl?

    - by Calvin Fisher
    I have a WSDL that the consumer of my web service expects will be adhered to strictly. I converted it into an interface with wsdl.exe and had my web service implement it. Except for this problem, I have been generally pleased with the results. A simple GetCurrentTime method will have the following response class generated from the WSDL in the interface definition: [System.CodeDobmCompiler.GeneratedCodeAttribute("wsdl", "2.0.50727.3038")] [System.SerializableAttribute()] [System.Diagnostics.DebuggerStepThroughAttribute()] [System.ComponentModel.DesignerCategoryAttribute("code")] [System.Xml.Serialization.XmlTypeAttribute(Namespace="[Client Namespace]")] public partial class GetCurrentTimeResponse { private System.DateTime timeStampField; [System.Xml.Serialization.XmlElementAttribute(Form=System.Xml.Schema.XmlSchemaForm.Unqualified] public System.DateTime TimeStamp{ // [accesses timeStampField] } } When I put the response data into the automatically generated response class, it gets serialized into an appropriate XML response. (Most of the web methods have much more complicated return types with multiple levels of arrays.) The problem is that the default serialization of DateTime objects violates one of the requirements in the WSDL: ... <xsd:simpleType name="SearchTimeStamp"> <xsd:restriction base="xsd:dateTime"> <xsd:pattern value="[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}(.[0-9]{1,7})?Z"> </xsd:restriction> </xsd:simpleType> ... Note the last part of the pattern where subseconds must be either 1 or 7 characters if they are included. The client seems to be rejecting the response because it does not match that requirement. The main issue is that when .NET serializes a DateTime object, it omits all trailing zeroes, meaning the resulting subsecond value varies in length. (e.g., "12:34:56.700" gets serialized as "<TimeStamp>12:34:56:7</TimeStamp>" by default). We use millisecond precision, so I need all timestamps to format with 7 subsecond digits in order to be compliant with the WSDL. It would be easy if I could specify a format string, but I'm not sure how to control the string that the DateTime object uses to serialize to XML, or to otherwise override the serialization behavior. How do I do this? Keeping in mind the following... I would like to modify the generated code as little as possible... preferably not at all if the change can be made through a partial class or inherited class. Using an inherited class for the return type of the web method will cause the web service to no longer implement the auto-generated interface. The TimeStamp type occurs in other, more complex response types. So, manually overriding the entire serialization process may be prohibitively time-consuming.

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