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  • Customize the SimpleMembership in ASP.NET MVC 4.0

    - by thangchung
    As we know, .NET 4.5 have come up to us, and come along with a lot of new interesting features as well. Visual Studio 2012 was also introduced some days ago. They made us feel very happy with cool improvement along with us. Performance when loading code editor is very good at the moment (immediate after click on the solution). I explore some of cool features at these days. Some of them like Json.NET integrated in ASP.NET MVC 4.0, improvement on asynchronous action, new lightweight theme on Visual Studio, supporting very good on mobile development, improvement on authentication… I reviewed them, and found out that in this version of .NET Microsoft was not only developed new feature that suggest from community but also focused on improvement performance of existing features or components. Besides that, they also opened source more projects, like Entity Framework, Reactive Extensions, ASP.NET Web Stack… At the moment, I feel Microsoft want to open source more and more their projects. Today, I am going to dive in deep on new SimpleMembership model. It is really good because in this security model, Microsoft actually focus on development needs. As we know, in the past, they introduce some of provider supplied for coding security like MembershipProvider, RoleProvider… I don’t need to talk but everyone that have ever used it know that they were actually hard to use, and not easy to maintain and unit testing. Why? Because every time you inherit it, you need to override all methods inside it. Some people try to abstract it by introduce more method with virtual keyword, and try to implement basic behavior, so in the subclass we only need to override the method that need for their business. But to me, it’s only the way to work around. ASP.NET team and Web Matrix knew about it, so they built the new features based on existing components on .NET framework. And one of component that comes to us is SimpleMembership and SimpleRole. They implemented the Façade pattern on the top of those, and called it is WebSecurity. In the web, we can call WebSecurity anywhere we want, and make a call to inside wrapper of it. I read a lot of them on web blog, on technical news, on MSDN as well. Matthew Osborn had an excellent article about it at his blog. Jon Galloway had an article like this at here. He analyzed why old membership provider not fixed well to ASP.NET MVC and how to get over it. Those are very good to me. It introduced to me about how to doing SimpleMembership on it, how to doing it on new ASP.NET MVC web application. But one thing, those didn’t tell me was how to doing it on existing security model (that mean we already had Users and Roles on legacy system, and how we can integrate it to this system), that’s a reason I will introduce it today. I have spent couples of hours to see what’s inside this, and try to make one example to clarify my concern. And it’s lucky that I can make it working well.The first thing, we need to create new ASP.NET MVC application on Visual Studio 2012. We need to choose Internet type for this web application. ASP.NET MVC actually creates all needs components for the basic membership and basic role. The cool feature is DoNetOpenAuth come along with it that means we can log-in using facebook, twitter or Windows Live if you want. But it’s only for LocalDb, so we need to change it to fix with existing database model on SQL Server. The next step we have to make SimpleMembership can understand which database we use and show it which column need to point to for the ID and UserName. I really like this feature because SimpleMembership on need to know about the ID and UserName, and they don’t care about rest of it. I assume that we have an existing database model like So we will point it in code like The codes for it, we put on InitializeSimpleMembershipAttribute like [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]     public sealed class InitializeSimpleMembershipAttribute : ActionFilterAttribute     {         private static SimpleMembershipInitializer _initializer;         private static object _initializerLock = new object();         private static bool _isInitialized;         public override void OnActionExecuting(ActionExecutingContext filterContext)         {             // Ensure ASP.NET Simple Membership is initialized only once per app start             LazyInitializer.EnsureInitialized(ref _initializer, ref _isInitialized, ref _initializerLock);         }         private class SimpleMembershipInitializer         {             public SimpleMembershipInitializer()             {                 try                 {                     WebSecurity.InitializeDatabaseConnection("DefaultDb", "User", "Id", "UserName", autoCreateTables: true);                 }                 catch (Exception ex)                 {                     throw new InvalidOperationException("The ASP.NET Simple Membership database could not be initialized. For more information, please see http://go.microsoft.com/fwlink/?LinkId=256588", ex);                 }             }         }     }And decorating it in the AccountController as below [Authorize]     [InitializeSimpleMembership]     public class AccountController : ControllerIn this case, assuming that we need to override the ValidateUser to point this to existing User database table, and validate it. We have to add one more class like public class CustomAdminMembershipProvider : SimpleMembershipProvider     {         // TODO: will do a better way         private const string SELECT_ALL_USER_SCRIPT = "select * from [dbo].[User]private where UserName = '{0}'";         private readonly IEncrypting _encryptor;         private readonly SimpleSecurityContext _simpleSecurityContext;         public CustomAdminMembershipProvider(SimpleSecurityContext simpleSecurityContext)             : this(new Encryptor(), new SimpleSecurityContext("DefaultDb"))         {         }         public CustomAdminMembershipProvider(IEncrypting encryptor, SimpleSecurityContext simpleSecurityContext)         {             _encryptor = encryptor;             _simpleSecurityContext = simpleSecurityContext;         }         public override bool ValidateUser(string username, string password)         {             if (string.IsNullOrEmpty(username))             {                 throw new ArgumentException("Argument cannot be null or empty", "username");             }             if (string.IsNullOrEmpty(password))             {                 throw new ArgumentException("Argument cannot be null or empty", "password");             }             var hash = _encryptor.Encode(password);             using (_simpleSecurityContext)             {                 var users =                     _simpleSecurityContext.Users.SqlQuery(                         string.Format(SELECT_ALL_USER_SCRIPT, username));                 if (users == null && !users.Any())                 {                     return false;                 }                 return users.FirstOrDefault().Password == hash;             }         }     }SimpleSecurityDataContext at here public class SimpleSecurityContext : DbContext     {         public DbSet<User> Users { get; set; }         public SimpleSecurityContext(string connStringName) :             base(connStringName)         {             this.Configuration.LazyLoadingEnabled = true;             this.Configuration.ProxyCreationEnabled = false;         }         protected override void OnModelCreating(DbModelBuilder modelBuilder)         {             base.OnModelCreating(modelBuilder);                          modelBuilder.Configurations.Add(new UserMapping());         }     }And Mapping for User as below public class UserMapping : EntityMappingBase<User>     {         public UserMapping()         {             this.Property(x => x.UserName);             this.Property(x => x.DisplayName);             this.Property(x => x.Password);             this.Property(x => x.Email);             this.ToTable("User");         }     }One important thing, you need to modify the web.config to point to our customize SimpleMembership <membership defaultProvider="AdminMemberProvider" userIsOnlineTimeWindow="15">       <providers>         <clear/>         <add name="AdminMemberProvider" type="CIK.News.Web.Infras.Security.CustomAdminMembershipProvider, CIK.News.Web.Infras" />       </providers>     </membership>     <roleManager enabled="false">       <providers>         <clear />         <add name="AdminRoleProvider" type="CIK.News.Web.Infras.Security.AdminRoleProvider, CIK.News.Web.Infras" />       </providers>     </roleManager>The good thing at here is we don’t need to modify the code on AccountController. We only need to modify on SimpleMembership and Simple Role (if need). Now build all solutions, run it. We should see a screen like thisIf I login to Twitter button at the bottom of this page, we will be transfer to twitter authentication pageYou have to waiting for a moment Afterwards it will transfer you back to your admin screenYou can find all source codes at my MSDN code. I will really happy if you guys feel free to put some comments as below. It will be helpful to improvement my code in the future. Thank for all your readings. 

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  • Introducing Data Annotations Extensions

    - by srkirkland
    Validation of user input is integral to building a modern web application, and ASP.NET MVC offers us a way to enforce business rules on both the client and server using Model Validation.  The recent release of ASP.NET MVC 3 has improved these offerings on the client side by introducing an unobtrusive validation library built on top of jquery.validation.  Out of the box MVC comes with support for Data Annotations (that is, System.ComponentModel.DataAnnotations) and can be extended to support other frameworks.  Data Annotations Validation is becoming more popular and is being baked in to many other Microsoft offerings, including Entity Framework, though with MVC it only contains four validators: Range, Required, StringLength and Regular Expression.  The Data Annotations Extensions project attempts to augment these validators with additional attributes while maintaining the clean integration Data Annotations provides. A Quick Word About Data Annotations Extensions The Data Annotations Extensions project can be found at http://dataannotationsextensions.org/, and currently provides 11 additional validation attributes (ex: Email, EqualTo, Min/Max) on top of Data Annotations’ original 4.  You can find a current list of the validation attributes on the afore mentioned website. The core library provides server-side validation attributes that can be used in any .NET 4.0 project (no MVC dependency). There is also an easily pluggable client-side validation library which can be used in ASP.NET MVC 3 projects using unobtrusive jquery validation (only MVC3 included javascript files are required). On to the Preview Let’s say you had the following “Customer” domain model (or view model, depending on your project structure) in an MVC 3 project: public class Customer { public string Email { get; set; } public int Age { get; set; } public string ProfilePictureLocation { get; set; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } When it comes time to create/edit this Customer, you will probably have a CustomerController and a simple form that just uses one of the Html.EditorFor() methods that the ASP.NET MVC tooling generates for you (or you can write yourself).  It should look something like this: With no validation, the customer can enter nonsense for an email address, and then can even report their age as a negative number!  With the built-in Data Annotations validation, I could do a bit better by adding a Range to the age, adding a RegularExpression for email (yuck!), and adding some required attributes.  However, I’d still be able to report my age as 10.75 years old, and my profile picture could still be any string.  Let’s use Data Annotations along with this project, Data Annotations Extensions, and see what we can get: public class Customer { [Email] [Required] public string Email { get; set; }   [Integer] [Min(1, ErrorMessage="Unless you are benjamin button you are lying.")] [Required] public int Age { get; set; }   [FileExtensions("png|jpg|jpeg|gif")] public string ProfilePictureLocation { get; set; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now let’s try to put in some invalid values and see what happens: That is very nice validation, all done on the client side (will also be validated on the server).  Also, the Customer class validation attributes are very easy to read and understand. Another bonus: Since Data Annotations Extensions can integrate with MVC 3’s unobtrusive validation, no additional scripts are required! Now that we’ve seen our target, let’s take a look at how to get there within a new MVC 3 project. Adding Data Annotations Extensions To Your Project First we will File->New Project and create an ASP.NET MVC 3 project.  I am going to use Razor for these examples, but any view engine can be used in practice.  Now go into the NuGet Extension Manager (right click on references and select add Library Package Reference) and search for “DataAnnotationsExtensions.”  You should see the following two packages: The first package is for server-side validation scenarios, but since we are using MVC 3 and would like comprehensive sever and client validation support, click on the DataAnnotationsExtensions.MVC3 project and then click Install.  This will install the Data Annotations Extensions server and client validation DLLs along with David Ebbo’s web activator (which enables the validation attributes to be registered with MVC 3). Now that Data Annotations Extensions is installed you have all you need to start doing advanced model validation.  If you are already using Data Annotations in your project, just making use of the additional validation attributes will provide client and server validation automatically.  However, assuming you are starting with a blank project I’ll walk you through setting up a controller and model to test with. Creating Your Model In the Models folder, create a new User.cs file with a User class that you can use as a model.  To start with, I’ll use the following class: public class User { public string Email { get; set; } public string Password { get; set; } public string PasswordConfirm { get; set; } public string HomePage { get; set; } public int Age { get; set; } } Next, create a simple controller with at least a Create method, and then a matching Create view (note, you can do all of this via the MVC built-in tooling).  Your files will look something like this: UserController.cs: public class UserController : Controller { public ActionResult Create() { return View(new User()); }   [HttpPost] public ActionResult Create(User user) { if (!ModelState.IsValid) { return View(user); }   return Content("User valid!"); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Create.cshtml: @model NuGetValidationTester.Models.User   @{ ViewBag.Title = "Create"; }   <h2>Create</h2>   <script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>   @using (Html.BeginForm()) { @Html.ValidationSummary(true) <fieldset> <legend>User</legend> @Html.EditorForModel() <p> <input type="submit" value="Create" /> </p> </fieldset> } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } In the Create.cshtml view, note that we are referencing jquery validation and jquery unobtrusive (jquery is referenced in the layout page).  These MVC 3 included scripts are the only ones you need to enjoy both the basic Data Annotations validation as well as the validation additions available in Data Annotations Extensions.  These references are added by default when you use the MVC 3 “Add View” dialog on a modification template type. Now when we go to /User/Create we should see a form for editing a User Since we haven’t yet added any validation attributes, this form is valid as shown (including no password, email and an age of 0).  With the built-in Data Annotations attributes we can make some of the fields required, and we could use a range validator of maybe 1 to 110 on Age (of course we don’t want to leave out supercentenarians) but let’s go further and validate our input comprehensively using Data Annotations Extensions.  The new and improved User.cs model class. { [Required] [Email] public string Email { get; set; }   [Required] public string Password { get; set; }   [Required] [EqualTo("Password")] public string PasswordConfirm { get; set; }   [Url] public string HomePage { get; set; }   [Integer] [Min(1)] public int Age { get; set; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now let’s re-run our form and try to use some invalid values: All of the validation errors you see above occurred on the client, without ever even hitting submit.  The validation is also checked on the server, which is a good practice since client validation is easily bypassed. That’s all you need to do to start a new project and include Data Annotations Extensions, and of course you can integrate it into an existing project just as easily. Nitpickers Corner ASP.NET MVC 3 futures defines four new data annotations attributes which this project has as well: CreditCard, Email, Url and EqualTo.  Unfortunately referencing MVC 3 futures necessitates taking an dependency on MVC 3 in your model layer, which may be unadvisable in a multi-tiered project.  Data Annotations Extensions keeps the server and client side libraries separate so using the project’s validation attributes don’t require you to take any additional dependencies in your model layer which still allowing for the rich client validation experience if you are using MVC 3. Custom Error Message and Globalization: Since the Data Annotations Extensions are build on top of Data Annotations, you have the ability to define your own static error messages and even to use resource files for very customizable error messages. Available Validators: Please see the project site at http://dataannotationsextensions.org/ for an up-to-date list of the new validators included in this project.  As of this post, the following validators are available: CreditCard Date Digits Email EqualTo FileExtensions Integer Max Min Numeric Url Conclusion Hopefully I’ve illustrated how easy it is to add server and client validation to your MVC 3 projects, and how to easily you can extend the available validation options to meet real world needs. The Data Annotations Extensions project is fully open source under the BSD license.  Any feedback would be greatly appreciated.  More information than you require, along with links to the source code, is available at http://dataannotationsextensions.org/. Enjoy!

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  • Red Gate Coder interviews: Robin Hellen

    - by Michael Williamson
    Robin Hellen is a test engineer here at Red Gate, and is also the latest coder I’ve interviewed. We chatted about debugging code, the roles of software engineers and testers, and why Vala is currently his favourite programming language. How did you get started with programming?It started when I was about six. My dad’s a professional programmer, and he gave me and my sister one of his old computers and taught us a bit about programming. It was an old Amiga 500 with a variant of BASIC. I don’t think I ever successfully completed anything! It was just faffing around. I didn’t really get anywhere with it.But then presumably you did get somewhere with it at some point.At some point. The PC emerged as the dominant platform, and I learnt a bit of Visual Basic. I didn’t really do much, just a couple of quick hacky things. A bit of demo animation. Took me a long time to get anywhere with programming, really.When did you feel like you did start to get somewhere?I think it was when I started doing things for someone else, which was my sister’s final year of university project. She called up my dad two days before she was due to submit, saying “We need something to display a graph!”. Dad says, “I’m too busy, go talk to your brother”. So I hacked up this ugly piece of code, sent it off and they won a prize for that project. Apparently, the graph, the bit that I wrote, was the reason they won a prize! That was when I first felt that I’d actually done something that was worthwhile. That was my first real bit of code, and the ugliest code I’ve ever written. It’s basically an array of pre-drawn line elements that I shifted round the screen to draw a very spikey graph.When did you decide that programming might actually be something that you wanted to do as a career?It’s not really a decision I took, I always wanted to do something with computers. And I had to take a gap year for uni, so I was looking for twelve month internships. I applied to Red Gate, and they gave me a job as a tester. And that’s where I really started having to write code well. To a better standard that I had been up to that point.How did you find coming to Red Gate and working with other coders?I thought it was really nice. I learnt so much just from other people around. I think one of the things that’s really great is that people are just willing to help you learn. Instead of “Don’t you know that, you’re so stupid”, it’s “You can just do it this way”.If you could go back to the very start of that internship, is there something that you would tell yourself?Write shorter code. I have a tendency to write massive, many-thousand line files that I break out of right at the end. And then half-way through a project I’m doing something, I think “Where did I write that bit that does that thing?”, and it’s almost impossible to find. I wrote some horrendous code when I started. Just that principle, just keep things short. Even if looks a bit crazy to be jumping around all over the place all of the time, it’s actually a lot more understandable.And how do you hold yourself to that?Generally, if a function’s going off my screen, it’s probably too long. That’s what I tell myself, and within the team here we have code reviews, so the guys I’m with at the moment are pretty good at pulling me up on, “Doesn’t that look like it’s getting a bit long?”. It’s more just the subjective standard of readability than anything.So you’re an advocate of code review?Yes, definitely. Both to spot errors that you might have made, and to improve your knowledge. The person you’re reviewing will say “Oh, you could have done it that way”. That’s how we learn, by talking to others, and also just sharing knowledge of how your project works around the team, or even outside the team. Definitely a very firm advocate of code reviews.Do you think there’s more we could do with them?I don’t know. We’re struggling with how to add them as part of the process without it becoming too cumbersome. We’ve experimented with a few different ways, and we’ve not found anything that just works.To get more into the nitty gritty: how do you like to debug code?The first thing is to do it in my head. I’ll actually think what piece of code is likely to have caused that error, and take a quick look at it, just to see if there’s anything glaringly obvious there. The next thing I’ll probably do is throw in print statements, or throw some exceptions from various points, just to check: is it going through the code path I expect it to? A last resort is to actually debug code using a debugger.Why is the debugger the last resort?Probably because of the environments I learnt programming in. VB and early BASIC didn’t have much of a debugger, the only way to find out what your program was doing was to add print statements. Also, because a lot of the stuff I tend to work with is non-interactive, if it’s something that takes a long time to run, I can throw in the print statements, set a run off, go and do something else, and look at it again later, rather than trying to remember what happened at that point when I was debugging through it. So it also gives me the record of what happens. I hate just sitting there pressing F5, F5, continually. If you’re having to find out what your code is doing at each line, you’ve probably got a very wrong mental model of what your code’s doing, and you can find that out just as easily by inspecting a couple of values through the print statements.If I were on some codebase that you were also working on, what should I do to make it as easy as possible to understand?I’d say short and well-named methods. The one thing I like to do when I’m looking at code is to find out where a value comes from, and the more layers of indirection there are, particularly DI [dependency injection] frameworks, the harder it is to find out where something’s come from. I really hate that. I want to know if the value come from the user here or is a constant here, and if I can’t find that out, that makes code very hard to understand for me.As a tester, where do you think the split should lie between software engineers and testers?I think the split is less on areas of the code you write and more what you’re designing and creating. The developers put a structure on the code, while my major role is to say which tests we should have, whether we should test that, or it’s not worth testing that because it’s a tiny function in code that nobody’s ever actually going to see. So it’s not a split in the code, it’s a split in what you’re thinking about. Saying what code we should write, but alternatively what code we should take out.In your experience, do the software engineers tend to do much testing themselves?They tend to control the lowest layer of tests. And, depending on how the balance of people is in the team, they might write some of the higher levels of test. Or that might go to the testers. I’m the only tester on my team with three other developers, so they’ll be writing quite a lot of the actual test code, with input from me as to whether we should test that functionality, whereas on other teams, where it’s been more equal numbers, the testers have written pretty much all of the high level tests, just because that’s the best use of resource.If you could shuffle resources around however you liked, do you think that the developers should be writing those high-level tests?I think they should be writing them occasionally. It helps when they have an understanding of how testing code works and possibly what assumptions we’ve made in tests, and they can say “actually, it doesn’t work like that under the hood so you’ve missed this whole area”. It’s one of those agile things that everyone on the team should be at least comfortable doing the various jobs. So if the developers can write test code then I think that’s a very good thing.So you think testers should be able to write production code?Yes, although given most testers skills at coding, I wouldn’t advise it too much! I have written a few things, and I did make a few changes that have actually gone into our production code base. They’re not necessarily running every time but they are there. I think having that mix of skill sets is really useful. In some ways we’re using our own product to test itself, so being able to make those changes where it’s not working saves me a round-trip through the developers. It can be really annoying if the developers have no time to make a change, and I can’t touch the code.If the software engineers are consistently writing tests at all levels, what role do you think the role of a tester is?I think on a team like that, those distinctions aren’t quite so useful. There’ll be two cases. There’s either the case where the developers think they’ve written good tests, but you still need someone with a test engineer mind-set to go through the tests and validate that it’s a useful set, or the correct set for that code. Or they won’t actually be pure developers, they’ll have that mix of test ability in there.I think having slightly more distinct roles is useful. When it starts to blur, then you lose that view of the tests as a whole. The tester job is not to create tests, it’s to validate the quality of the product, and you don’t do that just by writing tests. There’s more things you’ve got to keep in your mind. And I think when you blur the roles, you start to lose that end of the tester.So because you’re working on those features, you lose that holistic view of the whole system?Yeah, and anyone who’s worked on the feature shouldn’t be testing it. You always need to have it tested it by someone who didn’t write it. Otherwise you’re a bit too close and you assume “yes, people will only use it that way”, but the tester will come along and go “how do people use this? How would our most idiotic user use this?”. I might not test that because it might be completely irrelevant. But it’s coming in and trying to have a different set of assumptions.Are you a believer that it should all be automated if possible?Not entirely. So an automated test is always better than a manual test for the long-term, but there’s still nothing that beats a human sitting in front of the application and thinking “What could I do at this point?”. The automated test is very good but they follow that strict path, and they never check anything off the path. The human tester will look at things that they weren’t expecting, whereas the automated test can only ever go “Is that value correct?” in many respects, and it won’t notice that on the other side of the screen you’re showing something completely wrong. And that value might have been checked independently, but you always find a few odd interactions when you’re going through something manually, and you always need to go through something manually to start with anyway, otherwise you won’t know where the important bits to write your automation are.When you’re doing that manual testing, do you think it’s important to do that across the entire product, or just the bits that you’ve touched recently?I think it’s important to do it mostly on the bits you’ve touched, but you can’t ignore the rest of the product. Unless you’re dealing with a very, very self-contained bit, you’re almost always encounter other bits of the product along the way. Most testers I know, even if they are looking at just one path, they’ll keep open and move around a bit anyway, just because they want to find something that’s broken. If we find that your path is right, we’ll go out and hunt something else.How do you think this fits into the idea of continuously deploying, so long as the tests pass?With deploying a website it’s a bit different because you can always pull it back. If you’re deploying an application to customers, when you’ve released it, it’s out there, you can’t pull it back. Someone’s going to keep it, no matter how hard you try there will be a few installations that stay around. So I’d always have at least a human element on that path. With websites, you could probably automate straight out, or at least straight out to an internal environment or a single server in a cloud of fifty that will serve some people. But I don’t think you should release to everyone just on automated tests passing.You’ve already mentioned using BASIC and C# — are there any other languages that you’ve used?I’ve used a few. That’s something that has changed more recently, I’ve become familiar with more languages. Before I started at Red Gate I learnt a bit of C. Then last year, I taught myself Python which I actually really enjoyed using. I’ve also come across another language called Vala, which is sort of a C#-like language. It’s basically a pre-processor for C, but it has very nice syntax. I think that’s currently my favourite language.Any particular reason for trying Vala?I have a completely Linux environment at home, and I’ve been looking for a nice language, and C# just doesn’t cut it because I won’t touch Mono. So, I was looking for something like C# but that was useable in an open source environment, and Vala’s what I found. C#’s got a few features that Vala doesn’t, and Vala’s got a few features where I think “It would be awesome if C# had that”.What are some of the features that it’s missing?Extension methods. And I think that’s the only one that really bugs me. I like to use them when I’m writing C# because it makes some things really easy, especially with libraries that you can’t touch the internals of. It doesn’t have method overloading, which is sometimes annoying.Where it does win over C#?Everything is non-nullable by default, you never have to check that something’s unexpectedly null.Also, Vala has code contracts. This is starting to come in C# 4, but the way it works in Vala is that you specify requirements in short phrases as part of your function signature and they stick to the signature, so that when you inherit it, it has exactly the same code contract as the base one, or when you inherit from an interface, you have to match the signature exactly. Just using those makes you think a bit more about how you’re writing your method, it’s not an afterthought when you’ve got contracts from base classes given to you, you can’t change it. Which I think is a lot nicer than the way C# handles it. When are those actually checked?They’re checked both at compile and run-time. The compile-time checking isn’t very strong yet, it’s quite a new feature in the compiler, and because it compiles down to C, you can write C code and interface with your methods, so you can bypass that compile-time check anyway. So there’s an extra runtime check, and if you violate one of the contracts at runtime, it’s game over for your program, there’s no exception to catch, it’s just goodbye!One thing I dislike about C# is the exceptions. You write a bit of code and fifty exceptions could come from any point in your ten lines, and you can’t mentally model how those exceptions are going to come out, and you can’t even predict them based on the functions you’re calling, because if you’ve accidentally got a derived class there instead of a base class, that can throw a completely different set of exceptions. So I’ve got no way of mentally modelling those, whereas in Vala they’re checked like Java, so you know only these exceptions can come out. You know in advance the error conditions.I think Raymond Chen on Old New Thing says “the only thing you know when you throw an exception is that you’re in an invalid state somewhere in your program, so just kill it and be done with it!”You said you’ve also learnt bits of Python. How did you find that compared to Vala and C#?Very different because of the dynamic typing. I’ve been writing a website for my own use. I’m quite into photography, so I take photos off my camera, post-process them, dump them in a file, and I get a webpage with all my thumbnails. So sort of like Picassa, but written by myself because I wanted something to learn Python with. There are some things that are really nice, I just found it really difficult to cope with the fact that I’m not quite sure what this object type that I’m passed is, I might not ever be sure, so it can randomly blow up on me. But once I train myself to ignore that and just say “well, I’m fairly sure it’s going to be something that looks like this, so I’ll use it like this”, then it’s quite nice.Any particular features that you’ve appreciated?I don’t like any particular feature, it’s just very straightforward to work with. It’s very quick to write something in, particularly as you don’t have to worry that you’ve changed something that affects a different part of the program. If you have, then that part blows up, but I can get this part working right now.If you were doing a big project, would you be willing to do it in Python rather than C# or Vala?I think I might be willing to try something bigger or long term with Python. We’re currently doing an ASP.NET MVC project on C#, and I don’t like the amount of reflection. There’s a lot of magic that pulls values out, and it’s all done under the scenes. It’s almost managed to put a dynamic type system on top of C#, which in many ways destroys the language to me, whereas if you’re already in a dynamic language, having things done dynamically is much more natural. In many ways, you get the worst of both worlds. I think for web projects, I would go with Python again, whereas for anything desktop, command-line or GUI-based, I’d probably go for C# or Vala, depending on what environment I’m in.It’s the fact that you can gain from the strong typing in ways that you can’t so much on the web app. Or, in a web app, you have to use dynamic typing at some point, or you have to write a hell of a lot of boilerplate, and I’d rather use the dynamic typing than write the boilerplate.What do you think separates great programmers from everyone else?Probably design choices. Choosing to write it a piece of code one way or another. For any given program you ask me to write, I could probably do it five thousand ways. A programmer who is capable will see four or five of them, and choose one of the better ones. The excellent programmer will see the largest proportion and manage to pick the best one very quickly without having to think too much about it. I think that’s probably what separates, is the speed at which they can see what’s the best path to write the program in. More Red Gater Coder interviews

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  • NoSQL with MongoDB, NoRM and ASP.NET MVC - Part 2

    - by shiju
     In my last post, I have given an introduction to MongoDB and NoRM using an ASP.NET MVC demo app. I have updated the demo ASP.NET MVC app and a created a new drop at codeplex. You can download the demo at http://mongomvc.codeplex.com/In my last post, we have discussed to doing basic CRUD operations against a simple domain entity. In this post, let’s discuss on domain entity with deep object graph.The below is our domain entities  public class Category {       [MongoIdentifier]     public ObjectId Id { get; set; }       [Required(ErrorMessage = "Name Required")]     [StringLength(25, ErrorMessage = "Must be less than 25 characters")]     public string Name { get; set;}     public string Description { get; set; }     public List<Expense> Expenses { get; set; }       public Category()     {         Expenses = new List<Expense>();     } }    public class Expense {     [MongoIdentifier]     public ObjectId Id { get; set; }     public Category Category { get; set; }     public string  Transaction { get; set; }     public DateTime Date { get; set; }     public double Amount { get; set; }   }   We have two domain entities - Category and Expense. A single category contains a list of expense transactions and every expense transaction should have a Category.The MongoSession class  internal class MongoSession : IDisposable {     private readonly MongoQueryProvider provider;       public MongoSession()     {         this.provider = new MongoQueryProvider("Expense");     }       public IQueryable<Category> Categories     {         get { return new MongoQuery<Category>(this.provider); }     }     public IQueryable<Expense> Expenses     {         get { return new MongoQuery<Expense>(this.provider); }     }     public MongoQueryProvider Provider     {         get { return this.provider; }     }       public void Add<T>(T item) where T : class, new()     {         this.provider.DB.GetCollection<T>().Insert(item);     }       public void Dispose()     {         this.provider.Server.Dispose();     }     public void Delete<T>(T item) where T : class, new()     {         this.provider.DB.GetCollection<T>().Delete(item);     }       public void Drop<T>()     {         this.provider.DB.DropCollection(typeof(T).Name);     }       public void Save<T>(T item) where T : class,new()     {         this.provider.DB.GetCollection<T>().Save(item);                }     }     ASP.NET MVC view model  for Expense transaction  public class ExpenseViewModel {     public ObjectId Id { get; set; }       public ObjectId CategoryId { get; set; }       [Required(ErrorMessage = "Transaction Required")]            public string Transaction { get; set; }       [Required(ErrorMessage = "Date Required")]            public DateTime Date { get; set; }       [Required(ErrorMessage = "Amount Required")]        public double Amount { get; set; }       public IEnumerable<SelectListItem> Category { get; set; } }  Let's create action method for Insert and Update a expense transaction   [HttpPost] public ActionResult Save(ExpenseViewModel expenseViewModel) {     try     {         if (!ModelState.IsValid)         {             using (var session = new MongoSession())             {                 var categories = session.Categories.AsEnumerable<Category>();                 expenseViewModel.Category = categories.ToSelectListItems(expenseViewModel.CategoryId);                }             return View("Save", expenseViewModel);         }           var expense=new Expense();         ModelCopier.CopyModel(expenseViewModel, expense);           using (var session = new MongoSession())         {             ObjectId Id = expenseViewModel.CategoryId;             var category = session.Categories                 .Where(c => c.Id ==Id  )                 .FirstOrDefault();             expense.Category = category;             session.Save(expense);         }         return RedirectToAction("Index");     }     catch     {         return View();     } } Query with Expenses  using (var session = new MongoSession()) {     var expenses = session.Expenses.         Where(exp => exp.Date >= StartDate && exp.Date <= EndDate)         .AsEnumerable<Expense>(); }  We are doing a LINQ query expression with a Date filter. We can easily work with MongoDB using NoRM driver and can managing object graph of domain entities are pretty cool. Download the Source - You can download the source code form http://mongomvc.codeplex.com

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  • Handling WCF Service Paths in Silverlight 4 – Relative Path Support

    - by dwahlin
    If you’re building Silverlight applications that consume data then you’re probably making calls to Web Services. We’ve been successfully using WCF along with Silverlight for several client Line of Business (LOB) applications and passing a lot of data back and forth. Due to the pain involved with updating the ServiceReferences.ClientConfig file generated by a Silverlight service proxy (see Tim Heuer’s post on that subject to see different ways to deal with it) we’ve been using our own technique to figure out the service URL. Going that route makes it a peace of cake to switch between development, staging and production environments. To start, we have a ServiceProxyBase class that handles identifying the URL to use based on the XAP file’s location (this assumes that the service is in the same Web project that serves up the XAP file). The GetServiceUrlBase() method handles this work: public class ServiceProxyBase { public ServiceProxyBase() { if (!IsDesignTime) { ServiceUrlBase = GetServiceUrlBase(); } } public string ServiceUrlBase { get; set; } public static bool IsDesignTime { get { return (Application.Current == null) || (Application.Current.GetType() == typeof (Application)); } } public static string GetServiceUrlBase() { if (!IsDesignTime) { string url = Application.Current.Host.Source.OriginalString; return url.Substring(0, url.IndexOf("/ClientBin", StringComparison.InvariantCultureIgnoreCase)); } return null; } } Silverlight 4 now supports relative paths to services which greatly simplifies things.  We changed the code above to the following: public class ServiceProxyBase { private const string ServiceUrlPath = "../Services/JobPlanService.svc"; public ServiceProxyBase() { if (!IsDesignTime) { ServiceUrl = ServiceUrlPath; } } public string ServiceUrl { get; set; } public static bool IsDesignTime { get { return (Application.Current == null) || (Application.Current.GetType() == typeof (Application)); } } public static string GetServiceUrl() { if (!IsDesignTime) { return ServiceUrlPath; } return null; } } Our ServiceProxy class derives from ServiceProxyBase and handles creating the ABC’s (Address, Binding, Contract) needed for a WCF service call. Looking through the code (mainly the constructor) you’ll notice that the service URI is created by supplying the base path to the XAP file along with the relative path defined in ServiceProxyBase:   public class ServiceProxy : ServiceProxyBase, IServiceProxy { private const string CompletedEventargs = "CompletedEventArgs"; private const string Completed = "Completed"; private const string Async = "Async"; private readonly CustomBinding _Binding; private readonly EndpointAddress _EndPointAddress; private readonly Uri _ServiceUri; private readonly Type _ProxyType = typeof(JobPlanServiceClient); public ServiceProxy() { _ServiceUri = new Uri(Application.Current.Host.Source, ServiceUrl); var elements = new BindingElementCollection { new BinaryMessageEncodingBindingElement(), new HttpTransportBindingElement { MaxBufferSize = 2147483647, MaxReceivedMessageSize = 2147483647 } }; // order of entries in collection is significant: dumb _Binding = new CustomBinding(elements); _EndPointAddress = new EndpointAddress(_ServiceUri); } #region IServiceProxy Members /// <summary> /// Used to call a WCF service operation. /// </summary> /// <typeparam name="T">The type of EventArgs that will be returned by the service operation.</typeparam> /// <param name="callback">The method to call once the WCF call returns (the callback).</param> /// <param name="parameters">Any parameters that the service operation expects.</param> public void CallService<T>(EventHandler<T> callback, params object[] parameters) where T : EventArgs { try { var proxy = new JobPlanServiceClient(_Binding, _EndPointAddress); string action = typeof (T).Name.Replace(CompletedEventargs, String.Empty); _ProxyType.GetEvent(action + Completed).AddEventHandler(proxy, callback); _ProxyType.InvokeMember(action + Async, BindingFlags.InvokeMethod, null, proxy, parameters); } catch (Exception exp) { MessageBox.Show("Unable to use ServiceProxy.CallService to retrieve data: " + exp.Message); } } #endregion } The relative path support for calling services in Silverlight 4 definitely simplifies code and is yet another good reason to move from Silverlight 3 to Silverlight 4.   For more information about onsite, online and video training, mentoring and consulting solutions for .NET, SharePoint or Silverlight please visit http://www.thewahlingroup.com.

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  • Custom ASP.Net MVC 2 ModelMetadataProvider for using custom view model attributes

    - by SeanMcAlinden
    There are a number of ways of implementing a pattern for using custom view model attributes, the following is similar to something I’m using at work which works pretty well. The classes I’m going to create are really simple: 1. Abstract base attribute 2. Custom ModelMetadata provider which will derive from the DataAnnotationsModelMetadataProvider   Base Attribute MetadataAttribute using System; using System.Web.Mvc; namespace Mvc2Templates.Attributes {     /// <summary>     /// Base class for custom MetadataAttributes.     /// </summary>     public abstract class MetadataAttribute : Attribute     {         /// <summary>         /// Method for processing custom attribute data.         /// </summary>         /// <param name="modelMetaData">A ModelMetaData instance.</param>         public abstract void Process(ModelMetadata modelMetaData);     } } As you can see, the class simple has one method – Process. Process accepts the ModelMetaData which will allow any derived custom attributes to set properties on the model meta data and add items to its AdditionalValues collection.   Custom Model Metadata Provider For a quick explanation of the Model Metadata and how it fits in to the MVC 2 framework, it is basically a set of properties that are usually set via attributes placed above properties on a view model, for example the ReadOnly and HiddenInput attributes. When EditorForModel, DisplayForModel or any of the other EditorFor/DisplayFor methods are called, the ModelMetadata information is used to determine how to display the properties. All of the information available within the model metadata is also available through ViewData.ModelMetadata. The following class derives from the DataAnnotationsModelMetadataProvider built into the mvc 2 framework. I’ve overridden the CreateMetadata method in order to process any custom attributes that may have been placed above a property in a view model.   CustomModelMetadataProvider using System; using System.Collections.Generic; using System.Linq; using System.Web.Mvc; using Mvc2Templates.Attributes; namespace Mvc2Templates.Providers {     public class CustomModelMetadataProvider : DataAnnotationsModelMetadataProvider     {         protected override ModelMetadata CreateMetadata(             IEnumerable<Attribute> attributes,             Type containerType,             Func<object> modelAccessor,             Type modelType,             string propertyName)         {             var modelMetadata = base.CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName);               attributes.OfType<MetadataAttribute>().ToList().ForEach(x => x.Process(modelMetadata));               return modelMetadata;         }     } } As you can see, once the model metadata is created through the base method, a check for any attributes deriving from our new abstract base attribute MetadataAttribute is made, the Process method is then called on any existing custom attributes with the model meta data for the property passed in.   Hooking it up The last thing you need to do to hook it up is set the new CustomModelMetadataProvider as the current ModelMetadataProvider, this is done within the Global.asax Application_Start method. Global.asax protected void Application_Start()         {             AreaRegistration.RegisterAllAreas();               RegisterRoutes(RouteTable.Routes);               ModelMetadataProviders.Current = new CustomModelMetadataProvider();         }   In my next post, I’m going to demonstrate a cool custom attribute that turns a textbox into an ajax driven AutoComplete text box. Hope this is useful. Kind Regards, Sean McAlinden.

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  • Hierarchical View/ViewModel/Presenters in MVPVM

    - by Brian Flynn
    I've been working with MVVM for a while, but I've recently started using MVPVM and I want to know how to create hierarchial View/ViewModel/Presenter app using this pattern. In MVVM I would typically build my application using a hierarchy of Views and corresponding ViewModels e.g. I might define 3 views as follows: The View Models for these views would be as follows: public class AViewModel { public string Text { get { return "This is A!"; } } public object Child1 { get; set; } public object Child2 { get; set; } } public class BViewModel { public string Text { get { return "This is B!"; } } } public class CViewModel { public string Text { get { return "This is C!"; } } } In would then have some data templates to say that BViewModel and CViewModel should be presented using View B and View C: <DataTemplate DataType="{StaticResource local:BViewModel}"> <local:BView/> </DataTemplate> <DataTemplate DataType="{StaticResource local:CViewModel}"> <local:CView/> </DataTemplate> The final step would be to put some code in AViewModel that would assign values to Child1 and Child2: public AViewModel() { this.Child1 = new AViewModel(); this.Child2 = new BViewModel(); } The result of all this would be a screen that looks something like: Doing this in MVPVM would be fairly simple - simply moving the code in AViewModel's constructor to APresenter: public class APresenter { .... public void WireUp() { ViewModel.Child1 = new BViewModel(); ViewModel.Child2 = new CViewModel(); } } But If I want to have business logic for BViewModel and CViewModel I would need to have a BPresenter and a CPresenter - the problem is, Im not sure where the best place to put these are. I could store references to the presenter for AViewModel.Child1 and AViewModel.Child2 in APresenter i.e.: public class APresenter : IPresenter { private IPresenter child1Presenter; private IPresenter child2Presenter; public void WireUp() { child1Presenter = new BPresenter(); child1Presenter.WireUp(); child2Presenter = new CPresenter(); child2Presenter.WireUp(); ViewModel.Child1 = child1Presenter.ViewModel; ViewModel.Child2 = child2Presenter.ViewModel; } } But this solution seems inelegant compared to the MVVM approach. I have to keep track of both the presenter and the view model and ensure they stay in sync. If, for example, I wanted a button on View A, which, when clicked swapped the View's in Child1 and Child2, I might have a command that did the following: var temp = ViewModel.Child1; ViewModel.Child1 = ViewModel.Child2; ViewModel.Child2 = temp; This would work as far as swapping the view's on screen (assuming the correct Property Change notification code is in place), but now my APresenter.child1Presenter is pointing to the presenter for AViewModel.Child2, and APresenter.child2Presenter is pointing to the presenter for AViewModel.Child1. If something accesses APresenter.child1Presenter, any changes will actually happen to AViewModel.Child2. I can imagine this leading to all sorts of debugging fun. I know that I may be misunderstanding the pattern, and if this is the case a clarification of what Im doing wrong would be appreciated.

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

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

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  • Distinctly LINQ &ndash; Getting a Distinct List of Objects

    - by David Totzke
    Let’s say that you have a list of objects that contains duplicate items and you want to extract a subset of distinct items.  This is pretty straight forward in the trivial case where the duplicate objects are considered the same such as in the following example: List<int> ages = new List<int> { 21, 46, 46, 55, 17, 21, 55, 55 }; IEnumerable<int> distinctAges = ages.Distinct(); Console.WriteLine("Distinct ages:"); foreach (int age in distinctAges) { Console.WriteLine(age); } /* This code produces the following output: Distinct ages: 21 46 55 17 */ What if you are working with reference types instead?  Imagine a list of search results where items in the results, while unique in and of themselves, also point to a parent.  We’d like to be able to select a bunch of items in the list but then see only a distinct list of parents.  Distinct isn’t going to help us much on its own as all of the items are distinct already.  Perhaps we can create a class with just the information we are interested in like the Id and Name of the parents.  public class SelectedItem { public int ItemID { get; set; } public string DisplayName { get; set; } } We can then use LINQ to populate a list containing objects with just the information we are interested in and then get rid of the duplicates. IEnumerable<SelectedItem> list = (from item in ResultView.SelectedRows.OfType<Contract.ReceiptSelectResults>() select new SelectedItem { ItemID = item.ParentId, DisplayName = item.ParentName }) .Distinct(); Most of you will have guessed that this didn’t work.  Even though some of our objects are now duplicates, because we are working with reference types, it doesn’t matter that their properties are the same, they’re still considered unique.  What we need is a way to define equality for the Distinct() extension method. IEqualityComparer<T> Looking at the Distinct method we see that there is an overload that accepts an IEqualityComparer<T>.  We can simply create a class that implements this interface and that allows us to define equality for our SelectedItem class. public class SelectedItemComparer : IEqualityComparer<SelectedItem> { public new bool Equals(SelectedItem abc, SelectedItem def) { return abc.ItemID == def.ItemID && abc.DisplayName == def.DisplayName; } public int GetHashCode(SelectedItem obj) { string code = obj.DisplayName + obj.ItemID.ToString(); return code.GetHashCode(); } } In the Equals method we simply do whatever comparisons are necessary to determine equality and then return true or false.  Take note of the implementation of the GetHashCode method.  GetHashCode must return the same value for two different objects if our Equals method says they are equal.  Get this wrong and your comparer won’t work .  Even though the Equals method returns true, mismatched hash codes will cause the comparison to fail.  For our example, we simply build a string from the properties of the object and then call GetHashCode() on that. Now all we have to do is pass an instance of our IEqualitlyComarer<T> to Distinct and all will be well: IEnumerable<SelectedItem> list =     (from item in ResultView.SelectedRows.OfType<Contract.ReceiptSelectResults>()         select new SelectedItem { ItemID = item.dahfkp, DisplayName = item.document_code })                         .Distinct(new SelectedItemComparer());   Enjoy. Dave Just because I can… Technorati Tags: LINQ,C#

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  • Restricting Input in HTML Textboxes to Numeric Values

    - by Rick Strahl
    Ok, here’s a fairly basic one – how to force a textbox to accept only numeric input. Somebody asked me this today on a support call so I did a few quick lookups online and found the solutions listed rather unsatisfying. The main problem with most of the examples I could dig up was that they only include numeric values, but that provides a rather lame user experience. You need to still allow basic operational keys for a textbox – navigation keys, backspace and delete, tab/shift tab and the Enter key - to work or else the textbox will feel very different than a standard text box. Yes there are plug-ins that allow masked input easily enough but most are fixed width which is difficult to do with plain number input. So I took a few minutes to write a small reusable plug-in that handles this scenario. Imagine you have a couple of textboxes on a form like this: <div class="containercontent"> <div class="label">Enter a number:</div> <input type="text" name="txtNumber1" id="txtNumber1" value="" class="numberinput" /> <div class="label">Enter a number:</div> <input type="text" name="txtNumber2" id="txtNumber2" value="" class="numberinput" /> </div> and you want to restrict input to numbers. Here’s a small .forceNumeric() jQuery plug-in that does what I like to see in this case: [Updated thanks to Elijah Manor for a couple of small tweaks for additional keys to check for] <script type="text/javascript"> $(document).ready(function () { $(".numberinput").forceNumeric(); }); // forceNumeric() plug-in implementation jQuery.fn.forceNumeric = function () { return this.each(function () { $(this).keydown(function (e) { var key = e.which || e.keyCode; if (!e.shiftKey && !e.altKey && !e.ctrlKey && // numbers key >= 48 && key <= 57 || // Numeric keypad key >= 96 && key <= 105 || // comma, period and minus key == 190 || key == 188 || key == 109 || // Backspace and Tab and Enter key == 8 || key == 9 || key == 13 || // Home and End key == 35 || key == 36 || // left and right arrows key == 37 || key == 39 || // Del and Ins key == 46 || key == 45) return true; return false; }); }); } </script> With the plug-in in place in your page or an external .js file you can now simply use a selector to apply it: $(".numberinput").forceNumeric(); The plug-in basically goes through each selected element and hooks up a keydown() event handler. When a key is pressed the handler is fired and the keyCode of the event object is sent. Recall that jQuery normalizes the JavaScript Event object between browsers. The code basically white-lists a few key codes and rejects all others. It returns true to indicate the keypress is to go through or false to eat the keystroke and not process it which effectively removes it. Simple and low tech, and it works without too much change of typical text box behavior.© Rick Strahl, West Wind Technologies, 2005-2011Posted in JavaScript  jQuery  HTML  

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  • Start/Stop Window Service from ASP.NET page

    - by kaushalparik27
    Last week, I needed to complete one task on which I am going to blog about in this entry. The task is "Create a control panel like webpage to control (Start/Stop) Window Services which are part of my solution installed on computer where the main application is hosted". Here are the important points to accomplish:[1] You need to add System.ServiceProcess reference in your application. This namespace holds ServiceController Class to access the window service.[2] You need to check the status of the window services before you explicitly start or stop it.[3] By default, IIS application runs under ASP.NET account which doesn't have access rights permission to window service. So, Very Important part of the solution is: Impersonation. You need to impersonate the application/part of the code with the User Credentials which is having proper rights and permission to access the window service. If you try to access window service it will generate "access denied" error.The alternatives are: You can either impersonate whole application by adding Identity tag in web.cofig as:        <identity impersonate="true" userName="" password=""/>This tag will be under System.Web section. the "userName" and "password" will be the credentials of the user which is having rights to access the window service. But, this would not be a wise and good solution; because you may not impersonate whole website like this just to have access window service (which is going to be a small part of code).Second alternative is: Only impersonate part of code where you need to access the window service to start or stop it. I opted this one. But, to be fair; I am really unaware of the code part for impersonation. So, I just googled it and injected the code in my solution in a separate class file named as "Impersonate" with required static methods. In Impersonate class; impersonateValidUser() is the method to impersonate a part of code and undoImpersonation() is the method to undo the impersonation. Below is one example:  You need to provide domain name (which is "." if you are working on your home computer), username and password of appropriate user to impersonate.[4] Here, it is very important to note that: You need to have to store the Access Credentials (username and password) which you are going to user for impersonation; to some secured and encrypted format. I have used Machinekey Encryption to store the value encrypted value inside database.[5] So now; The real part is to start or stop a window service. You are almost done; because ServiceController class has simple Start() and Stop() methods to start or stop a window service. A ServiceController class has parametrized constructor that takes name of the service as parameter.Code to Start the window service: Code to Stop the window service: Isn't that too easy! ServiceController made it easy :) I have attached a working example with this post here to start/stop "SQLBrowser" service where you need to provide proper credentials who have permission to access to window service.  hope it would helps./.

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  • A Closer Look at the HiddenInput Attribute in MVC 2

    - by Steve Michelotti
    MVC 2 includes an attribute for model metadata called the HiddenInput attribute. The typical usage of the attribute looks like this (line #3 below): 1: public class PersonViewModel 2: { 3: [HiddenInput(DisplayValue = false)] 4: public int? Id { get; set; } 5: public string FirstName { get; set; } 6: public string LastName { get; set; } 7: } So if you displayed your PersonViewModel with Html.EditorForModel() or Html.EditorFor(m => m.Id), the framework would detect the [HiddenInput] attribute metadata and produce HTML like this: 1: <input id="Id" name="Id" type="hidden" value="21" /> This is pretty straight forward and allows an elegant way to keep the technical key for your model (e.g., a Primary Key from the database) in the HTML so that everything will be wired up correctly when the form is posted to the server and of course not displaying this value visually to the end user. However, when I was giving a recent presentation, a member of the audience asked me (quite reasonably), “When would you ever set DisplayValue equal to true when using a HiddenInput?” To which I responded, “Well, it’s an edge case. There are sometimes when…er…um…people might want to…um…display this value to the user.” It was quickly apparent to me (and I’m sure everyone else in the room) what a terrible answer this was. I realized I needed to have a much better answer here. First off, let’s look at what is produced if we change our view model to use “true” (which is equivalent to use specifying [HiddenInput] since “true” is the default) on line #3: 1: public class PersonViewModel 2: { 3: [HiddenInput(DisplayValue = true)] 4: public int? Id { get; set; } 5: public string FirstName { get; set; } 6: public string LastName { get; set; } 7: } Will produce the following HTML if rendered from Htm.EditorForModel() in your view: 1: <div class="editor-label"> 2: <label for="Id">Id</label> 3: </div> 4: <div class="editor-field"> 5: 21<input id="Id" name="Id" type="hidden" value="21" /> 6: <span class="field-validation-valid" id="Id_validationMessage"></span> 7: </div> The key is line #5. We get the text of “21” (which happened to be my DB Id in this instance) and also a hidden input element (again with “21”). So the question is, why would one want to use this? The best answer I’ve found is contained in this MVC 2 whitepaper: When a view lets users edit the ID of an object and it is necessary to display the value as well as to provide a hidden input element that contains the old ID so that it can be passed back to the controller. Well, that actually makes sense. Yes, it seems like something that would happen *rarely* but, for those instances, it would enable them easily. It’s effectively equivalent to doing this in your view: 1: <%: Html.LabelFor(m => m.Id) %> 2: <%: Model.Id %> 3: <%: Html.HiddenFor(m => m.Id) %> But it’s allowing you to specify it in metadata on your view model (and thereby take advantage of templated helpers like Html.EditorForModel() and Html.EditorFor()) rather than having to explicitly specifying everything in your view.

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  • Reverse subarray of an array with O(1)

    - by Babibu
    I have an idea how to implement sub array reverse with O(1), not including precalculation such as reading the input. I will have many reverse operations, and I can't use the trivial solution of O(N). Edit: To be more clear I want to build data structure behind the array with access layer that knows about reversing requests and inverts the indexing logic as necessary when someone wants to iterate over the array. Edit 2: The data structure will only be used for iterations I been reading this and this and even this questions but they aren't helping. There are 3 cases that need to be taking care of: Regular reverse operation Reverse that including reversed area Intersection between reverse and part of other reversed area in the array Here is my implementation for the first two parts, I will need your help with the last one. This is the rule class: class Rule { public int startingIndex; public int weight; } It is used in my basic data structure City: public class City { Rule rule; private static AtomicInteger _counter = new AtomicInteger(-1); public final int id = _counter.incrementAndGet(); @Override public String toString() { return "" + id; } } This is the main class: public class CitiesList implements Iterable<City>, Iterator<City> { private int position; private int direction = 1; private ArrayList<City> cities; private ArrayDeque<City> citiesQeque = new ArrayDeque<>(); private LinkedList<Rule> rulesQeque = new LinkedList<>(); public void init(ArrayList<City> cities) { this.cities = cities; } public void swap(int index1, int index2){ Rule rule = new Rule(); rule.weight = Math.abs(index2 - index1); cities.get(index1).rule = rule; cities.get(index2 + 1).rule = rule; } @Override public void remove() { throw new IllegalStateException("Not implemented"); } @Override public City next() { City city = cities.get(position); if (citiesQeque.peek() == city){ citiesQeque.pop(); changeDirection(); position += (city.rule.weight + 1) * direction; city = cities.get(position); } if(city.rule != null){ if(city.rule != rulesQeque.peekLast()){ rulesQeque.add(city.rule); position += city.rule.weight * direction; changeDirection(); citiesQeque.push(city); } else{ rulesQeque.removeLast(); position += direction; } } else{ position += direction; } return city; } private void changeDirection() { direction *= -1; } @Override public boolean hasNext() { return position < cities.size(); } @Override public Iterator<City> iterator() { position = 0; return this; } } And here is a sample program: public static void main(String[] args) { ArrayList<City> list = new ArrayList<>(); for(int i = 0 ; i < 20; i++){ list.add(new City()); } CitiesList citiesList = new CitiesList(); citiesList.init(list); for (City city : citiesList) { System.out.print(city + " "); } System.out.println("\n******************"); citiesList.swap(4, 8); for (City city : citiesList) { System.out.print(city + " "); } System.out.println("\n******************"); citiesList.swap(2, 15); for (City city : citiesList) { System.out.print(city + " "); } } How do I handle reverse intersections?

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  • RPi and Java Embedded GPIO: Writing Java code to blink LED

    - by hinkmond
    So, you've followed the previous steps to install Java Embedded on your Raspberry Pi ?, you went to Fry's and picked up some jumper wires, LEDs, and resistors ?, you hooked up the wires, LED, and resistor the the correct pins ?, and now you want to start programming in Java on your RPi? Yes? ???????! OK, then... Here we go. You can use the following source code to blink your first LED on your RPi using Java. In the code you can see that I'm not using any complicated gpio libraries like wiringpi or pi4j, and I'm not doing any low-level pin manipulation like you can in C. And, I'm not using python (hell no!). This is Java programming, so we keep it simple (and more readable) than those other programming languages. See: Write Java code to do this In the Java code, I'm opening up the RPi Debian Wheezy well-defined file handles to control the GPIO ports. First I'm resetting everything using the unexport/export file handles. (On the RPi, if you open the well-defined file handles and write certain ASCII text to them, you can drive your GPIO to perform certain operations. See this GPIO reference). Next, I write a "1" then "0" to the value file handle of the GPIO0 port (see the previous pinout diagram). That makes the LED blink. Then, I loop to infinity. Easy, huh? import java.io.* /* * Java Embedded Raspberry Pi GPIO app */ package jerpigpio; import java.io.FileWriter; /** * * @author hinkmond */ public class JerpiGPIO { static final String GPIO_OUT = "out"; static final String GPIO_ON = "1"; static final String GPIO_OFF = "0"; static final String GPIO_CH00="0"; /** * @param args the command line arguments */ public static void main(String[] args) { FileWriter commandFile; try { /*** Init GPIO port for output ***/ // Open file handles to GPIO port unexport and export controls FileWriter unexportFile = new FileWriter("/sys/class/gpio/unexport"); FileWriter exportFile = new FileWriter("/sys/class/gpio/export"); // Reset the port unexportFile.write(GPIO_CH00); unexportFile.flush(); // Set the port for use exportFile.write(GPIO_CH00); exportFile.flush(); // Open file handle to port input/output control FileWriter directionFile = new FileWriter("/sys/class/gpio/gpio"+GPIO_CH00+"/direction"); // Set port for output directionFile.write(GPIO_OUT); directionFile.flush(); /*--- Send commands to GPIO port ---*/ // Opne file handle to issue commands to GPIO port commandFile = new FileWriter("/sys/class/gpio/gpio"+GPIO_CH00+"/value"); // Loop forever while (true) { // Set GPIO port ON commandFile.write(GPIO_ON); commandFile.flush(); // Wait for a while java.lang.Thread.sleep(200); // Set GPIO port OFF commandFile.write(GPIO_OFF); commandFile.flush(); // Wait for a while java.lang.Thread.sleep(200); } } catch (Exception exception) { exception.printStackTrace(); } } } Hinkmond

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  • Using Managed Beans with your ADF Mobile Client Applications

    - by [email protected]
    Did you know it's easy to extend your ADF Mobile Client application with a Managed Bean just like it is with an ADF web application?  Here's how: Using the New Gallery (File -> New), create a new Java class.  This class should extend oracle.adfnmc.el.utils.BeanResolver.         Add this java class as a managed bean: Go to your task flow, select the Overview tab at the bottom and go to the Managed Bean section.  Add an entry and name your new Managed Bean and point to the java class you just created.        Add your custom methods and properties to your java class   Since reflection is not supported in the J2ME version on some platforms (BlackBerry), you need to provide dispatch code if you want to invoke/access any of your methods/properties from EL.  Here's a sample:  MyBeanClass.java    Use Expression Language (EL) to access your properties and invoke your methods on your MCX pages.  Here's an sample:     <?xml version="1.0" encoding="UTF-8" ?><amc:view xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"          xmlns:amc="http://xmlns.oracle.com/jdev/amc">  <amc:form id="form0">    <amc:menuControl refId="menu0"/>    <amc:panelGroupLayout id="panelGroupLayout1" width="100%">      <amc:panelGroupLayout id="panelGroupLayout2" layout="horizontal"                            width="100%">        <amc:image id="image1" source="logo_sm.png"/>        <amc:outputText value="Home" id="outputText1" verticalAlign="center"                        fontSize="20" fontWeight="bold"                        foregroundColor="#ff0000"/>      </amc:panelGroupLayout>      <amc:commandLink text="#{MyBean.property1}" id="commandLink1"                       actionListener="#{MyBean.doFoo}"                       foregroundColor="#0000ff" action="patientlist"/>    </amc:panelGroupLayout>  </amc:form>  <amc:menu type="main" id="menu0">    <amc:menuGroup id="menuGroup1">      <amc:commandMenuItem id="commandMenuItem1" action="exit" label="Exit"                           index="1" weight="0"/>    </amc:menuGroup>  </amc:menu></amc:view> 

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  • Unit Testing DateTime – The Crazy Way

    - by João Angelo
    We all know that the process of unit testing code that depends on DateTime, particularly the current time provided through the static properties (Now, UtcNow and Today), it’s a PITA. If you go ask how to unit test DateTime.Now on stackoverflow I’ll bet that you’ll get two kind of answers: Encapsulate the current time in your own interface and use a standard mocking framework; Pull out the big guns like Typemock Isolator, JustMock or Microsoft Moles/Fakes and mock the static property directly. Now each alternative has is pros and cons and I would have to say that I glean more to the second approach because the first adds a layer of abstraction just for the sake of testability. However, the second approach depends on commercial tools that not every shop wants to buy or in the not so friendly Microsoft Moles. (Sidenote: Moles is now named Fakes and it will ship with VS 2012) This tends to leave people without an acceptable and simple solution so after reading another of these types of questions in SO I came up with yet another alternative, one based on the first alternative that I presented here but tries really hard to not get in your way with yet another layer of abstraction. So, without further dues, I present you, the Tardis. The Tardis is single section of conditionally compiled code that overrides the meaning of the DateTime expression inside a single class. You still get the normal coding experience of using DateTime all over the place, but in a DEBUG compilation your tests will be able to mock every static method or property of the DateTime class. An example follows, while the full Tardis code can be downloaded from GitHub: using System; using NSubstitute; using NUnit.Framework; using Tardis; public class Example { public Example() : this(string.Empty) { } public Example(string title) { #if DEBUG this.DateTime = DateTimeProvider.Default; this.Initialize(title); } internal IDateTimeProvider DateTime { get; set; } internal Example(string title, IDateTimeProvider provider) { this.DateTime = provider; #endif this.Initialize(title); } private void Initialize(string title) { this.Title = title; this.CreatedAt = DateTime.UtcNow; } private string title; public string Title { get { return this.title; } set { this.title = value; this.UpdatedAt = DateTime.UtcNow; } } public DateTime CreatedAt { get; private set; } public DateTime UpdatedAt { get; private set; } } public class TExample { public void T001() { // Arrange var tardis = Substitute.For<IDateTimeProvider>(); tardis.UtcNow.Returns(new DateTime(2000, 1, 1, 6, 6, 6)); // Act var sut = new Example("Title", tardis); // Assert Assert.That(sut.CreatedAt, Is.EqualTo(tardis.UtcNow)); } public void T002() { // Arrange var tardis = Substitute.For<IDateTimeProvider>(); var sut = new Example("Title", tardis); tardis.UtcNow.Returns(new DateTime(2000, 1, 1, 6, 6, 6)); // Act sut.Title = "Updated"; // Assert Assert.That(sut.UpdatedAt, Is.EqualTo(tardis.UtcNow)); } } This approach is also suitable for other similar classes with commonly used static methods or properties like the ConfigurationManager class.

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  • Windows Workflow Foundation (WF) and things I were more intuitive

    - by pjohnson
    I've started using Windows Workflow Foundation, and so far ran into a few things that aren't incredibly obvious. Microsoft did a good job of providing a ton of samples, which is handy because you need them to get anywhere with WF. The docs are thin, so I've been bouncing between samples and downloadable labs to figure out how to implement various activities in a workflow. Code separation or not? You can create a workflow and activity in Visual Studio with or without code separation, i.e. just a .cs "Component" style object with a Designer.cs file, or a .xoml XML markup file with code behind (beside?) it. Absence any obvious advantage to one or the other, I used code separation for workflows and any complex custom activities, and without code separation for custom activities that just inherit from the Activity class and thus don't have anything special in the designer. So far, so good. Service - In the WF world, this is simply a class that talks to the workflow about things outside the workflow, not to be confused with how the term "service" is used in every other context I've seen in the Windows and .NET world, i.e. an executable that waits for events or requests from a client and services them (Windows service, web service, WCF service, etc.). ListenActivity - Such a great concept, yet so unintuitive. It seems you need at least two branches (EventDrivenActivity instances), one for your positive condition and one for a timeout. The positive condition has a HandleExternalEventActivity, and the timeout has a DelayActivity followed by however you want to handle the delay, e.g. a ThrowActivity. The timeout is simple enough; wiring up the HandleExternalEventActivity is where things get fun. You need to create a service (see above), and an interface for that service (this seems more complex than should be necessary--why not have activities just wire to a service directly?). And you need to create a custom EventArgs class that inherits from ExternalDataEventArgs--you can't create an ExternalDataEventArgs event handler directly, even if you don't need to add any more information to the event args, despite ExternalDataEventArgs not being marked as an abstract class, nor a compiler error nor warning nor any other indication that you're doing something wrong, until you run it and find that it always times out and get to check every place mentioned here to see why. Your interface and service need an event that consumes your custom EventArgs class, and a method to fire that event. You need to call that method from somewhere. Then you get to hope that you did everything just right, or that you can step through code in the debugger before your Delay timeout expires. Yes, it's as much fun as it sounds. TransactionScopeActivity - I had the bright idea of putting one in as a placeholder, then filling in the database updates later. That caused this error: The workflow hosting environment does not have a persistence service as required by an operation on the workflow instance "[GUID]". ...which is about as helpful as "Object reference not set to an instance of an object" and even more fun to debug. Google led me to this Microsoft Forums hit, and from there I figured out it didn't like that the activity had no children. Again, a Validator on TransactionScopeActivity would have pointed this out to me at design time, rather than handing me a nearly useless error at runtime. Easily enough, I disabled the activity and that fixed it. I still see huge potential in my work where WF could make things easier and more flexible, but there are some seriously rough edges at the moment. Maybe I'm just spoiled by how much easier and more intuitive development elsewhere in the .NET Framework is.

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  • Measuring Code Quality

    - by DotNetBlues
    Several months back, I was tasked with measuring the quality of code in my organization. Foolishly, I said, "No problem." I figured that Visual Studio has a built-in code metrics tool (Analyze -> Calculate Code Metrics) and that would be a fine place to start with. I was right, but also very wrong. The Visual Studio calculates five primary metrics: Maintainability Index, Cyclomatic Complexity, Depth of Inheritance, Class Coupling, and Lines of Code. The first two are figured at the method level, the second at (primarily) the class level, and the last is a simple count. The first question any reasonable person should ask is "Which one do I look at first?" The first question any manager is going to ask is, "What one number tells me about the whole application?" My answer to both, in a way, was "Maintainability Index." Why? Because each of the other numbers represent one element of quality while MI is a composite number that includes Cyclomatic Complexity. I'd be lying if I said no consideration was given to the fact that it was abstract enough that it's harder for some surly developer (I've been known to resemble that remark) to start arguing why a high coupling or inheritance is no big deal or how complex requirements are to blame for complex code. I should also note that I don't think there is one magic bullet metric that will tell you objectively how good a code base is. There are a ton of different metrics out there, and each one was created for a specific purpose in mind and has a pet theory behind it. When you've got a group of developers who aren't accustomed to measuring code quality, picking a 0-100 scale, non-controversial metric that can be easily generated by tools you already own really isn't a bad place to start. That sort of answers the question a developer would ask, but what about the management question; how do you dashboard this stuff when Visual Studio doesn't roll up the numbers to the solution level? Since VS does roll up the MI to the project level, I thought I could just figure out what sort of weighting Microsoft used to roll method scores up to the class level and then to the namespace and project levels. I was a bit surprised by the answer: there is no weighting. That means that a class with one 1300 line method (which will score a 0 MI) and one empty constructor (which will score a 100 MI) will have an overall MI of a respectable 50. Throw in a couple of DTOs that are nothing more than getters and setters (which tend to score 95 or better) and the project ends up looking really, really healthy. The next poor bastard who has to work on the application is probably not going to be singing the praises of its maintainability, though. For the record, that 1300 line method isn't a hypothetical, either. So, what does one do with that? Well, I decided to weight the average by the Lines of Code per method. For our above example, the formula for the class's MI becomes ((1300 * 0) + (1 * 100))/1301 = .077, rounded to 0. Sounds about right. Continue the pattern for namespace, project, solution, and even multi-solution application MI scores. This can be done relatively easily by using the "export to Excel" button and running a quick formula against the data. On the short list of follow-up questions would be, "How do I improve my application's score?" That's an answer for another time, though.

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  • WebGrid Helper and Complex Types

    - by imran_ku07
        Introduction:           WebGrid helper makes it very easy to show tabular data. It was originally designed for ASP.NET Web Pages(WebMatrix) to display, edit, page and sort tabular data but you can also use this helper in ASP.NET Web Forms and ASP.NET MVC. When using this helper, sometimes you may run into a problem if you use complex types in this helper. In this article, I will show you how you can use complex types in WebGrid helper.       Description:             Let's say you need to show the employee data and you have the following classes,   public class Employee { public string Name { get; set; } public Address Address { get; set; } public List<string> ContactNumbers { get; set; } } public class Address { public string City { get; set; } }               The Employee class contain a Name, an Address and list of ContactNumbers. You may think that you can easily show City in WebGrid using Address.City, but no. The WebGrid helper will throw an exception at runtime if any Address property is null in the Employee list. Also, you cannot directly show ContactNumbers property. The easiest way to show these properties is to add some additional properties,   public Address NotNullableAddress { get { return Address ?? new Address(); } } public string Contacts { get { return string.Join("; ",ContactNumbers); } }               Now you can easily use these properties in WebGrid. Here is the complete code of this example,  @functions{ public class Employee { public Employee(){ ContactNumbers = new List<string>(); } public string Name { get; set; } public Address Address { get; set; } public List<string> ContactNumbers { get; set; } public Address NotNullableAddress { get { return Address ?? new Address(); } } public string Contacts { get { return string.Join("; ",ContactNumbers); } } } public class Address { public string City { get; set; } } } @{ var myClasses = new List<Employee>{ new Employee { Name="A" , Address = new Address{ City="AA" }, ContactNumbers = new List<string>{"021-216452","9231425651"}}, new Employee { Name="C" , Address = new Address{ City="CC" }}, new Employee { Name="D" , ContactNumbers = new List<string>{"045-14512125","21531212121"}} }; var grid = new WebGrid(source: myClasses); } @grid.GetHtml(columns: grid.Columns( grid.Column("NotNullableAddress.City", header: "City"), grid.Column("Name"), grid.Column("Contacts")))                    Summary:           You can use WebGrid helper to show tabular data in ASP.NET MVC, ASP.NET Web Forms and  ASP.NET Web Pages. Using this helper, you can also show complex types in the grid. In this article, I showed you how you use complex types with WebGrid helper. Hopefully you will enjoy this article too.  

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  • Handling null values and missing object properties in Silverlight 4

    - by PeterTweed
    Before Silverlight 4 to bind a data object to the UI and display a message associated with either a null value or if the binding path was wrong, you would need to write a Converter.  In Silverlight 4 we find the addition of the markup extensions TargetNullValue and FallbackValue that allows us to display a value when a null value is found in the bound to property and display a value when the property being bound to is not found. This post will show you how to use both markup extensions. Steps: 1. Create a new Silverlight 4 application 2. In the body of the MainPage.xaml.cs file replace the MainPage class with the following code:     public partial class MainPage : UserControl     {         public MainPage()         {             InitializeComponent();             this.Loaded += new RoutedEventHandler(MainPage_Loaded);         }           void MainPage_Loaded(object sender, RoutedEventArgs e)         {             person p = new person() { NameValue = "Peter Tweed" };             this.DataContext = p;         }     }       public class person     {         public string NameValue { get; set; }         public string TitleValue { get; set; }     } This code defines a class called person with two properties.  A new instance of the class is created, only defining the value for one of the properties and bound to the DataContext of the page. 3.  In the MainPage.xaml file copy the following XAML into the LayoutRoot grid:         <Grid.RowDefinitions>             <RowDefinition Height="60*" />             <RowDefinition Height="28*" />             <RowDefinition Height="28*" />             <RowDefinition Height="30*" />             <RowDefinition Height="154*" />         </Grid.RowDefinitions>         <Grid.ColumnDefinitions>             <ColumnDefinition Width="86*" />             <ColumnDefinition Width="314*" />         </Grid.ColumnDefinitions>         <TextBlock Grid.Row="1" Height="23" HorizontalAlignment="Left" Margin="32,0,0,0" Name="textBlock1" Text="Name Value:" VerticalAlignment="Top" />         <TextBlock Grid.Row="2" Height="23" HorizontalAlignment="Left" Margin="32,0,0,0" Name="textBlock2" Text="Title Value:" VerticalAlignment="Top" />         <TextBlock Grid.Row="3" Height="23" HorizontalAlignment="Left" Margin="32,0,0,0" Name="textBlock3" Text="Non Existant Value:" VerticalAlignment="Top" />         <TextBlock Grid.Column="1" Grid.Row="1" Height="23" HorizontalAlignment="Left" Name="textBlock4" Text="{Binding NameValue, TargetNullValue='No Name!!!!!!!'}" VerticalAlignment="Top" Margin="6,0,0,0" />         <TextBlock Grid.Column="1" Grid.Row="2" Height="23" HorizontalAlignment="Left" Name="textBlock5" Text="{Binding TitleValue, TargetNullValue='No Title!!!!!!!'}" VerticalAlignment="Top" Margin="6,0,0,0" />         <TextBlock Grid.Column="1" Grid.Row="3" Height="23" HorizontalAlignment="Left" Margin="6,0,0,0" Name="textBlock6" Text="{Binding AgeValue, FallbackValue='No such property!'}" VerticalAlignment="Top" />    This XAML defines three textblocks – two of which use the TargetNull and one that uses the FallbackValue markup extensions.  4. Run the application and see the person name displayed as defined for the person object, the expected string displayed for the TargetNullValue when no value exists for the boudn property and the expected string displayed for the FallbackValue when the property bound to is not found on the bound object. It's that easy!

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  • BizTalk Testing Series - The xpath Function

    - by Michael Stephenson
    Background While the xpath function in a BizTalk orchestration is a very powerful feature I have often come across the situation where someone has hard coded an xpath expression in an orchestration. If you have read some of my previous posts about testing I've tried to get across the general theme like test-driven or test-assisted development approaches where the underlying principle is that your building up your solution of small well tested units that are put together and the resulting solution is usually quite robust. You will be finding more bugs within your unit tests and fewer outside of your team. The thing I don't like about the xpath functions usual usage is when you come across an orchestration which has something like the below snippet in an expression or assign shape: string result = xpath(myMessage,"string(//Order/OrderItem/ProductName)"); My main issue with this is that the xpath statement is hard coded in the orchestration and you don't really know it works until you are running the orchestration. Some of the problems I think you end up with are: You waste time with lengthy debugging of the orchestration when your statement isn't working You might not know the function isn't working quite as expected because the testable unit around it is big You are much more open to regression issues if your schema changes     Approach to Testing The technique I usually follow is to hold the xpath statement as a constant in a helper class or to format a constant with a helper function to get the actual xpath statement. It is then used by the orchestration like follows. string result = xpath(myMessage, MyHelperClass.ProductNameXPathStatement); This means that because the xpath statement is available outside of the orchestration it now becomes testable in its own right. This means: I can test it in its own right I'm less likely to waste time tracking down problems caused by an error in the statement I can reduce the risk or regression issuess I'm now able to implement some testing around my xpath statements which usually are something like the following:    The test will use a sample xml file The sample will be validated against the schema The test will execute the xpath statement and then check the results are as expected     Walk-through BizTalk uses the XPathNavigator internally behind the xpath function to implement the queries you will usually use using the navigators select or evaluate functions. In the sample (link at bottom) I have a small solution which contains a schema from which I have generated a sample instance. I will then use this instance as the basis for my tests.     In the below diagram you can see the helper class which I've encapsulated my xpath expressions in, and some helper functions which will format the expression in the case of a repeating node which would want to inject an index into the xpath query.             I have then created a test class which has some functions to execute some queries against my sample xml file. An example of this is below.         In the test class I have a couple of helper functions which will execute the xpath expressions in a similar way to BizTalk. You could have a proper helper class to do this if you wanted.         You can see now in the BizTalk expression editor I can use these functions alongside the xpath function.         Conclusion I hope you can see with very little effort you can make your life much easier by testing xpath statements outside of an orchestration rather than using them directly hard coded into the orchestration.     This can also save you lots of pain longer term because your build should break if your schema changes unexpectedly causing these xpath tests to fail where as your tests around the orchestration will be more difficult to troubleshoot and workout the cause of the problem.     Sample Link The sample is available from the following link: http://code.msdn.microsoft.com/testbtsxpathfunction     Other Tools On the subject of using the xpath function, if you don't already use it the below tool is very useful for creating your xpath statements (thanks BizBert) http://www.bizbert.com/bizbert/2007/11/30/XPath+The+Hidden+Language+Of+BizTalk.aspx

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  • C# 5 Async, Part 2: Asynchrony Today

    - by Reed
    The .NET Framework has always supported asynchronous operations.  However, different mechanisms for supporting exist throughout the framework.  While there are at least three separate asynchronous patterns used through the framework, only the latest is directly usable with the new Visual Studio Async CTP.  Before delving into details on the new features, I will talk about existing asynchronous code, and demonstrate how to adapt it for use with the new pattern. The first asynchronous pattern used in the .NET framework was the Asynchronous Programming Model (APM).  This pattern was based around callbacks.  A method is used to start the operation.  It typically is named as BeginSomeOperation.  This method is passed a callback defined as an AsyncCallback, and returns an object that implements IAsyncResult.  Later, the IAsyncResult is used in a call to a method named EndSomeOperation, which blocks until completion and returns the value normally directly returned from the synchronous version of the operation.  Often, the EndSomeOperation call would be called from the callback function passed, which allows you to write code that never blocks. While this pattern works perfectly to prevent blocking, it can make quite confusing code, and be difficult to implement.  For example, the sample code provided for FileStream’s BeginRead/EndRead methods is not simple to understand.  In addition, implementing your own asynchronous methods requires creating an entire class just to implement the IAsyncResult. Given the complexity of the APM, other options have been introduced in later versions of the framework.  The next major pattern introduced was the Event-based Asynchronous Pattern (EAP).  This provides a simpler pattern for asynchronous operations.  It works by providing a method typically named SomeOperationAsync, which signals its completion via an event typically named SomeOperationCompleted. The EAP provides a simpler model for asynchronous programming.  It is much easier to understand and use, and far simpler to implement.  Instead of requiring a custom class and callbacks, the standard event mechanism in C# is used directly.  For example, the WebClient class uses this extensively.  A method is used, such as DownloadDataAsync, and the results are returned via the DownloadDataCompleted event. While the EAP is far simpler to understand and use than the APM, it is still not ideal.  By separating your code into method calls and event handlers, the logic of your program gets more complex.  It also typically loses the ability to block until the result is received, which is often useful.  Blocking often requires writing the code to block by hand, which is error prone and adds complexity. As a result, .NET 4 introduced a third major pattern for asynchronous programming.  The Task<T> class introduced a new, simpler concept for asynchrony.  Task and Task<T> effectively represent an operation that will complete at some point in the future.  This is a perfect model for thinking about asynchronous code, and is the preferred model for all new code going forward.  Task and Task<T> provide all of the advantages of both the APM and the EAP models – you have the ability to block on results (via Task.Wait() or Task<T>.Result), and you can stay completely asynchronous via the use of Task Continuations.  In addition, the Task class provides a new model for task composition and error and cancelation handling.  This is a far superior option to the previous asynchronous patterns. The Visual Studio Async CTP extends the Task based asynchronous model, allowing it to be used in a much simpler manner.  However, it requires the use of Task and Task<T> for all operations.

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  • RPi and Java Embedded GPIO: Sensor Reading using Java Code

    - by hinkmond
    And, now to program the Java code for reading the fancy-schmancy static electricity sensor connected to your Raspberry Pi, here is the source code we'll use: First, we need to initialize ourselves... /* * Java Embedded Raspberry Pi GPIO Input app */ package jerpigpioinput; import java.io.FileWriter; import java.io.RandomAccessFile; import java.text.DateFormat; import java.text.SimpleDateFormat; import java.util.Calendar; /** * * @author hinkmond */ public class JerpiGPIOInput { static final String GPIO_IN = "in"; // Add which GPIO ports to read here static String[] GpioChannels = { "7" }; /** * @param args the command line arguments */ public static void main(String[] args) { try { /*** Init GPIO port(s) for input ***/ // Open file handles to GPIO port unexport and export controls FileWriter unexportFile = new FileWriter("/sys/class/gpio/unexport"); FileWriter exportFile = new FileWriter("/sys/class/gpio/export"); for (String gpioChannel : GpioChannels) { System.out.println(gpioChannel); // Reset the port unexportFile.write(gpioChannel); unexportFile.flush(); // Set the port for use exportFile.write(gpioChannel); exportFile.flush(); // Open file handle to input/output direction control of port FileWriter directionFile = new FileWriter("/sys/class/gpio/gpio" + gpioChannel + "/direction"); // Set port for input directionFile.write(GPIO_IN); directionFile.flush(); } And, next we will open up a RandomAccessFile pointer to the GPIO port. /*** Read data from each GPIO port ***/ RandomAccessFile[] raf = new RandomAccessFile[GpioChannels.length]; int sleepPeriod = 10; final int MAXBUF = 256; byte[] inBytes = new byte[MAXBUF]; String inLine; int zeroCounter = 0; // Get current timestamp with Calendar() Calendar cal; DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss.SSS"); String dateStr; // Open RandomAccessFile handle to each GPIO port for (int channum=0; channum Then, loop forever to read in the values to the console. // Loop forever while (true) { // Get current timestamp for latest event cal = Calendar.getInstance(); dateStr = dateFormat.format(cal.getTime()); // Use RandomAccessFile handle to read in GPIO port value for (int channum=0; channum Rinse, lather, and repeat... Compile this Java code on your host PC or Mac with javac from the JDK. Copy over the JAR or class file to your Raspberry Pi, "sudo -i" to become root, then start up this Java app in a shell on your RPi. That's it! You should see a "1" value get logged each time you bring a statically charged item (like a balloon you rub on the cat) near the antenna of the sensor. There you go. You've just seen how Java Embedded technology on the Raspberry Pi is an easy way to access sensors. Hinkmond

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  • How to write simple code using TDD [migrated]

    - by adeel41
    Me and my colleagues do a small TDD-Kata practice everyday for 30 minutes. For reference this is the link for the excercise http://osherove.com/tdd-kata-1/ The objective is to write better code using TDD. This is my code which I've written public class Calculator { public int Add( string numbers ) { const string commaSeparator = ","; int result = 0; if ( !String.IsNullOrEmpty( numbers ) ) result = numbers.Contains( commaSeparator ) ? AddMultipleNumbers( GetNumbers( commaSeparator, numbers ) ) : ConvertToNumber( numbers ); return result; } private int AddMultipleNumbers( IEnumerable getNumbers ) { return getNumbers.Sum(); } private IEnumerable GetNumbers( string separator, string numbers ) { var allNumbers = numbers .Replace( "\n", separator ) .Split( new string[] { separator }, StringSplitOptions.RemoveEmptyEntries ); return allNumbers.Select( ConvertToNumber ); } private int ConvertToNumber( string number ) { return Convert.ToInt32( number ); } } and the tests for this class are [TestFixture] public class CalculatorTests { private int ArrangeAct( string numbers ) { var calculator = new Calculator(); return calculator.Add( numbers ); } [Test] public void Add_WhenEmptyString_Returns0() { Assert.AreEqual( 0, ArrangeAct( String.Empty ) ); } [Test] [Sequential] public void Add_When1Number_ReturnNumber( [Values( "1", "56" )] string number, [Values( 1, 56 )] int expected ) { Assert.AreEqual( expected, ArrangeAct( number ) ); } [Test] public void Add_When2Numbers_AddThem() { Assert.AreEqual( 3, ArrangeAct( "1,2" ) ); } [Test] public void Add_WhenMoreThan2Numbers_AddThemAll() { Assert.AreEqual( 6, ArrangeAct( "1,2,3" ) ); } [Test] public void Add_SeparatorIsNewLine_AddThem() { Assert.AreEqual( 6, ArrangeAct( @"1 2,3" ) ); } } Now I'll paste code which they have written public class StringCalculator { private const char Separator = ','; public int Add( string numbers ) { const int defaultValue = 0; if ( ShouldReturnDefaultValue( numbers ) ) return defaultValue; return ConvertNumbers( numbers ); } private int ConvertNumbers( string numbers ) { var numberParts = GetNumberParts( numbers ); return numberParts.Select( ConvertSingleNumber ).Sum(); } private string[] GetNumberParts( string numbers ) { return numbers.Split( Separator ); } private int ConvertSingleNumber( string numbers ) { return Convert.ToInt32( numbers ); } private bool ShouldReturnDefaultValue( string numbers ) { return String.IsNullOrEmpty( numbers ); } } and the tests [TestFixture] public class StringCalculatorTests { [Test] public void Add_EmptyString_Returns0() { ArrangeActAndAssert( String.Empty, 0 ); } [Test] [TestCase( "1", 1 )] [TestCase( "2", 2 )] public void Add_WithOneNumber_ReturnsThatNumber( string numberText, int expected ) { ArrangeActAndAssert( numberText, expected ); } [Test] [TestCase( "1,2", 3 )] [TestCase( "3,4", 7 )] public void Add_WithTwoNumbers_ReturnsSum( string numbers, int expected ) { ArrangeActAndAssert( numbers, expected ); } [Test] public void Add_WithThreeNumbers_ReturnsSum() { ArrangeActAndAssert( "1,2,3", 6 ); } private void ArrangeActAndAssert( string numbers, int expected ) { var calculator = new StringCalculator(); var result = calculator.Add( numbers ); Assert.AreEqual( expected, result ); } } Now the question is which one is better? My point here is that we do not need so many small methods initially because StringCalculator has no sub classes and secondly the code itself is so simple that we don't need to break it up too much that it gets confusing after having so many small methods. Their point is that code should read like english and also its better if they can break it up earlier than doing refactoring later and third when they will do refactoring it would be much easier to move these methods quite easily into separate classes. My point of view against is that we never made a decision that code is difficult to understand so why we are breaking it up so early. So I need a third person's opinion to understand which option is much better.

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  • Handling Configuration Changes in Windows Azure Applications

    - by Your DisplayName here!
    While finalizing StarterSTS 1.5, I had a closer look at lifetime and configuration management in Windows Azure. (this is no new information – just some bits and pieces compiled at one single place – plus a bit of reality check) When dealing with lifetime management (and especially configuration changes), there are two mechanisms in Windows Azure – a RoleEntryPoint derived class and a couple of events on the RoleEnvironment class. You can find good documentation about RoleEntryPoint here. The RoleEnvironment class features two events that deal with configuration changes – Changing and Changed. Whenever a configuration change gets pushed out by the fabric controller (either changes in the settings section or the instance count of a role) the Changing event gets fired. The event handler receives an instance of the RoleEnvironmentChangingEventArgs type. This contains a collection of type RoleEnvironmentChange. This in turn is a base class for two other classes that detail the two types of possible configuration changes I mentioned above: RoleEnvironmentConfigurationSettingsChange (configuration settings) and RoleEnvironmentTopologyChange (instance count). The two respective classes contain information about which configuration setting and which role has been changed. Furthermore the Changing event can trigger a role recycle (aka reboot) by setting EventArgs.Cancel to true. So your typical job in the Changing event handler is to figure if your application can handle these configuration changes at runtime, or if you rather want a clean restart. Prior to the SDK 1.3 VS Templates – the following code was generated to reboot if any configuration settings have changed: private void RoleEnvironmentChanging(object sender, RoleEnvironmentChangingEventArgs e) {     // If a configuration setting is changing     if (e.Changes.Any(change => change is RoleEnvironmentConfigurationSettingChange))     {         // Set e.Cancel to true to restart this role instance         e.Cancel = true;     } } This is a little drastic as a default since most applications will work just fine with changed configuration – maybe that’s the reason this code has gone away in the 1.3 SDK templates (more). The Changed event gets fired after the configuration changes have been applied. Again the changes will get passed in just like in the Changing event. But from this point on RoleEnvironment.GetConfigurationSettingValue() will return the new values. You can still decide to recycle if some change was so drastic that you need a restart. You can use RoleEnvironment.RequestRecycle() for that (more). As a rule of thumb: When you always use GetConfigurationSettingValue to read from configuration (and there is no bigger state involved) – you typically don’t need to recycle. In the case of StarterSTS, I had to abstract away the physical configuration system and read the actual configuration (either from web.config or the Azure service configuration) at startup. I then cache the configuration settings in memory. This means I indeed need to take action when configuration changes – so in my case I simply clear the cache, and the new config values get read on the next access to my internal configuration object. No downtime – nice! Gotcha A very natural place to hook up the RoleEnvironment lifetime events is the RoleEntryPoint derived class. But with the move to the full IIS model in 1.3 – the RoleEntryPoint methods get executed in a different AppDomain (even in a different process) – see here.. You might no be able to call into your application code to e.g. clear a cache. Keep that in mind! In this case you need to handle these events from e.g. global.asax.

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