There is no thread

Nice read from Stephen Cleary about threading in .Net / Windows:

There is no thread

Asynchronous Programming Model

This is a good explanation of how to make asynchronous calls with the Asynchronous Programming Model ( begin/end):

Calling Synchronous Methods Asynchronously

Competing consumers and returning results with in-memory-queues (BlockingCollection)

I needed a way to to put some work in a queue, consume it and return the result to the producer of the work. In C# we can use the BlockingCollection class and TaskCompletionSource for that.

The code in this blogpost is based on the code from Albahari.

What I want to do is this create a Producer which creates work and places that on a queue. I'll also want to create Consumers which take work off the queue and send the result back to the Producer when they are done. See the following image for an overview:

Let's start with a simple console application:
(Don't forget to set it to the correct framework, as VS 2010 defaults to client framework 4.0)

class Program
{
   static void Main()
   {
      // Put something on a queue
   }
}


This is the class that we are going to put on the queue:



public class WorkItem
{
   public readonly TaskCompletionSource<int> TaskSource;
   public readonly int Context;
   public readonly CancellationToken? CancelToken;

   public WorkItem(
      TaskCompletionSource<int> taskSource,
      int context,
      CancellationToken? cancelToken)
   {
      TaskSource = taskSource;
      Context = context;
      CancelToken = cancelToken;
   }

}


Next we create the queue we are going to use for enqueueing the work:


public class ProducerConsumerQueue : IDisposable
{
   readonly BlockingCollection<WorkItem> _workitemQueue =
      new BlockingCollection<WorkItem>();

   public Task<int> EnqueueTask(int context)
   {
      return EnqueueTask(context, null);
   }

   public Task<int> EnqueueTask(int context,
                                   CancellationToken? cancelToken)
   {
      var tcs = new TaskCompletionSource<int>();
      _workitemQueue.Add(new WorkItem(tcs, context, cancelToken));
      return tcs.Task;
   }

   public void Dispose()
   {
      _workitemQueue.CompleteAdding();
   }
}


As you can see our ProducerConsumerQueue uses a BlockingCollection internally. This is a great class that let's multiple consumers/workers read from it in a thread-safe manner.

Next, create the consumer:



public class Consumer
{
   private readonly BlockingCollection<WorkItem> _workitemQueue;

   public Consumer(BlockingCollection<WorkItem> workitemQueue)
   {
      _workitemQueue = workitemQueue;
   }

   public void Consume()
   {
      foreach (WorkItem workItem in _workitemQueue.GetConsumingEnumerable())
      {
         if (workItem.CancelToken.HasValue &&
             workItem.CancelToken.Value.IsCancellationRequested)
         {
            workItem.TaskSource.SetCanceled();
         }
         else
         {
            try
            {
               Thread.Sleep(1000); // simulate work

               workItem.TaskSource.SetResult(workItem.Context + 1);
            }
            catch (OperationCanceledException ex)
            {
               if (ex.CancellationToken == workItem.CancelToken)
               {
                  workItem.TaskSource.SetCanceled();
               }
               else
               {
                  workItem.TaskSource.SetException(ex);
               }
            }
            catch (Exception ex)
            {
               workItem.TaskSource.SetException(ex);
            }
         }
      }
   }

}

So how do we start the consumers?

We do that in the constructor of the ProducerConsumerQueue:

   public ProducerConsumerQueue(int workerCount)
   {
      for (int i = 0; i < workerCount; i++)
      {
         var consumer = new Consumer(_workitemQueue);

         Task.Factory.StartNew(consumer.Consume);
      }
   }

Finally we can finish the console application:

class Program
{
   static void Main()
   {
      var producerConsumerQueue = new ProducerConsumerQueue(2);

      Task<int> task1 = producerConsumerQueue.EnqueueTask(1);
      Task<int> task2 = producerConsumerQueue.EnqueueTask(2);
      Task<int> task3 = producerConsumerQueue.EnqueueTask(3);

      Console.WriteLine(task1.Result);
      Console.WriteLine(task2.Result);
      Console.WriteLine(task3.Result);

      Console.ReadLine();
   }
}


If we run this, we will start three tasks. Each task will get an input value, add one to it, and return the value to the console app. WE start with two consumers, so after one second the first two tasks finish and the following output is printed:

2
3

A second later the third task finished, and we will see this:

4

You can play around with the number of consumers and the number of enqueued WorkItems.

Design Patterns Quick Reference

Jason McDonald made a Quick Reference for Design Patterns. You can get it here:

http://www.mcdonaldland.info/2007/11/28/40/

Call WCF service with ADFS token

How can we configure a WCF client to call an ADFS-secured WCF service? In this blog I'll show you how to do it with code only, no xml-configuration needed.

The are only two steps to take:

1. Get a securityToken from ADFS
2. Create a WCF channel to the WCF service, using the securityToken.

Create the WCF client

To get started, let's create a console application that will be the client:

internal class Program
{
   private static void Main()
   {
      var stsEndpoint =
            "https://myAdfsServer/adfs/services/trust/13/certificatemixed";
      var clientCertificateThumbprint = "[put the thumbprint here]";
      var svcEndpoint = "https://myDomain/myService.svc";

      var token = GetToken(stsEndpoint, svcEndpoint);
      var channel = CreateChannel<IMyService>(token,
                                              svcEndpoint,
                                              clientCertificateThumbprint);

      channel.Foo();
   }
}

How to get a secured token from ADFS?

The GetToken() method looks like this:

private static SecurityToken GetToken(string stsEndpoint,
                                      string svcEndpoint,
                                      string thumbprint)
{
   var binding = new
       CertificateWSTrustBinding(SecurityMode.TransportWithMessageCredential);
   
   var factory = new WSTrustChannelFactory(binding, stsEndpoint)
                            {
                               TrustVersion = TrustVersion.WSTrust13
                            };

    factory.Credentials.ClientCertificate.SetCertificate(
                                                StoreLocation.LocalMachine,
                                                StoreName.My,
                                                X509FindType.FindByThumbprint,
                                                thumbprint);

   var rst = new RequestSecurityToken
                      {
                         RequestType = WSTrust13Constants.RequestTypes.Issue,
                         AppliesTo = new EndpointAddress(svcEndpoint),
                         KeyType = WSTrust13Constants.KeyTypes.Symmetric
                      };

   var channel = factory.CreateChannel();

   var token = channel.Issue(rst);

   return token;
}

Please note that I'm using a client certificate, and not Username/Password to authenticate.

With the token, the secured channel can be created, like this:

private static T CreateChannel<T>(SecurityToken token, string svcEndpoint) where T : class

{

   var binding = new WS2007FederationHttpBinding(

                   WSFederationHttpSecurityMode.TransportWithMessageCredential

                                                                      );

   binding.Security.Message.EstablishSecurityContext = true;

   binding.Security.Message.IssuedKeyType = SecurityKeyType.SymmetricKey;

   var factory = new ChannelFactory<T>(binding, svcEndpoint);

   factory.ConfigureChannelFactory();

   // Turn Cardspace off

   factory.Credentials.SupportInteractive = false;

   var channel = factory.CreateChannelWithIssuedToken(token);

            

   return channel;

}

IoC containers compared

There are quite a few different IoC containers for .Net. How does one decide which IoC container to use? There are performance comparisons made, but as even the slowest IoC container only takes 0.04 milliseconds to resolve a dependency, performance is not a good discriminator.
I've decided to do a feature comparisons of Autofac, Structuremap and Unity. The results can be read below.

Basic registration

Basic registration is easy in each of the frameworks.

Structuremap

ObjectFactory.Initialize(x =>

{
   x.For<ISomethingService>()
     .Use<SomethingService>();
}

Autofac

var builder = new ContainerBuilder();

builder.RegisterType<SomethingService>()
          .As<ISomethingService>();

Unity

IUnityContainer container = new UnityContainer();

container.RegisterType<ISomethingService, SomethingService>();

Registration of a singleton

Setting lifetimescope options like "singleton" are easy in each of the frameworks.

Structuremap

ObjectFactory.Initialize(x =>

{
   x.For<IThatService>()
     .Singleton()
     .Use<ThatService>();

}

Autofac

var builder = new ContainerBuilder();

builder.RegisterType<ThatService>()
          .As<IThatService>()
          .SingleInstance();

Unity

IUnityContainer container = new UnityContainer();

container.RegisterType<IThatService, ThatService>(
                                                                new ContainerControlledLifetimeManager());

Personally I don't like the term ContainerControlledLifetimeManager. Structuremap and Autofac have more obvious terms (Singleton and SingleInstance).

Autoscanning assemblies

Some frameworks provide ways to automatically register all or specific classes from an assembly. This can really be helpfull if for example you want to register all repositories in your solution and you don't want to write every registration by hand.

Structuremap

ObjectFactory.Initialize(x =>

{
   x.Scan(a =>
             {
                a.Assembly("[AssemblyName]");
                a.WithDefaultConventions();
             });

}


Structuremap can autoscan assemblies, but you can't set any lifetimeoptions. If you want to do that, you have to write some custom code.

Autofac

var builder = new ContainerBuilder();


builder.RegisterAssemblyTypes(Assembly.Load("[AssemblyName]"))
                .Where(t => t.Name.EndsWith("Repository"))
                .AsImplementedInterfaces()
                .SingleInstance();


Autofac has the option to set lifetimeoptions. In the example above all repositories are registered as singletons (SingleInstance).

Unity

As far as I know, Unity doesn't provide a way to autoscan assemblies out of the box.
With Unity you can autoregister assemblies by using Unity Auto Registration. (Thanks to Björn Bailleul for letting me know).

Organizing registrations

In real-life you want to organize the registrations and not put everything in the global.asax.

Structuremap

public class UnitOfWorkRegistry : Registry
{
   public UnitOfWorkRegistry()
   {
      For<IUnitOfWork>().Singleton().Use<UnitOfWork>();
   }
}


ObjectFactory.Initialize(x =>

{
   x.AddRegistry<UnitOfWorkRegistry>();
}


Structuremap doesn't have a way to set any properties or pass constructor variables to the Registry.

Autofac

public class MyModule : Autofac.Module

{

   public bool RandomProperty { get; set; }

   protected override void Load(ContainerBuilder builder)

   {

      if (RandomProperty)

         builder.RegisterType<UnitOfWork>().As<IUnitOfWork>().SingleInstance();

   }

}

builder.RegisterModule(new MyModule() { RandomProperty = true });

Unity

I didn't find a way to use modules or registries with Unity. If anyone knows how to do this, please let me know.

Documentation

Structuremap

The documentation of Structuremap is incomplete and outdated. For example the next text can be seen on the homepage of structuremap:

The current version 2.5.2 was released in January 2009, with a 2.6 release scheduled for no later than the end of January 2009.

At the moment of writing this blog the current version of Structuremap is 2.6.4.1 and updated on august 13, 2012. But there are more problematic errors, like the quickstart, which says you can use the next statement to register a type:

x.ForRequestedType<IValidator>()
 .TheDefaultIsConcreteType<Validator>();

And indeed you can, but the ForRequestedType and TheDefaultIsConcreteType are deprecated, so they shouldn't be on the quickstart anymore.

Another major gap in the documentation is that there's no information about ASP.Net MVC integration on the Structuremap homepage.

Autofac

I have no criticism on the Autofac documentation. It is frequently updated (last update was 59 minutes ago since writing this text), and it's extensive. The most important chapters are easy to be found on the wiki on the Autofac homepage.

Unity

I find it difficult to find the documentation on Unity. This is the path I had to follow for the online documentation:

1. Go to the Unity homepage (http://unity.codeplex.com/)
2. Click on the Documentation tab (http://unity.codeplex.com/documentation)
3. Click on the link to MSDN (http://msdn.microsoft.com/en-us/library/ff647202)
4. Click on the link to Unity 3 (http://msdn.microsoft.com/en-us/library/dn170416.aspx)
5. I've found only a link to a guide that can be downloaded, not what I was looking for.
6. Click on the link to Unity 2.0 (http://msdn.microsoft.com/en-us/library/ff663144.aspx)
7. Found the online info about configuring Unity (http://msdn.microsoft.com/en-us/library/ff660846(v=pandp.20).aspx)

The online documentation itself is extensive and tedious. I find it diffucult to navigate. For example the text about MVC integration is nowhere to be found.

The PDF that can be downloaded looks a lot more inviting than the online documentation.

Final verdict

Autofac has the most extensive featureset when it comes to registration of classes. The documentation is up to date and easy to read.

Structuremap does a pretty good job too, but lacks in autoscanning features. The documentation is outdated.

Unity doesn't provide a way to autoscan assemblies, which leads to writing a lot of code yourself if you need that. (corrected by remark of Björn Bailleul) I didn't find a way to organize the registrations like the way it can be done with Autofac or Structuremap. The documentation is hard to find and difficult to navigate.

Fluent Factory Method with Lambda's

In a previous article I showed you the Fluent Interface / Fluent Builder pattern. If you want to build a nice factory method you can use that pattern. But there's another option; factory with lambda expressions. then you can wrtite a factory method that you can use like this:


var validator = ValidatorFactory.New(config =>
      {
         config.HasName("Test");
         config.UseThatValidator();
       });

validator.Validate();

How does it work?

In this example we have two validators that implement the IValidator interface:

public interface IValidator
{
   void Validate();
}


public class ThisValidator : IValidator
{
   private string _name;

   public void Validate()
   {
      // Do something
   }
}


public class ThatValidator : IValidator
{
   private string _name;

   public void Validate()
   {
      // Do something
   }
}

Next we need a Configurator that can be used the the factory later:

public class ValidatorConfigurator
{
}

As you can see ThisValidator and ThatValidator have a name, so we need to have a way to configure that name. Let's add a method to the ValidatorConfigurator to set the name:



public class ValidatorConfigurator
{
   internal string _name;


   public ValidatorConfigurator HasName(string name)
   {
      _name = name;
      return this;
   }

}


This is the factory that we'll be using:



public static class ValidatorFactory

{
   public static IValidator New()
   {
   }
}




At this stage we can only call the New() method of the factory:

var validator = ValidatorFactory.New();

Add a lambda expression

We can't write a lambda expression as parameter of the New() method. How do we fix that? The easiest way is to add an Action with the Configuration as type:


public static class ValidatorFactory

{
   public static IValidator New(Action<ValidatorConfigurator> applySettings)
   {
   }
}



And this is what we can do with the factory now:

var validator = ValidatorFactory.New(x=>x.HasName("BestValidatorEver"));

Create a validator in the Factory

The New() method of the factory does nothing now. So we won't get a valid Validator back. Let's add some code to the New() method:


public static class ValidatorFactory

{
   public static IValidator New(Action<ValidatorConfigurator> applySettings)
   {
      // We need to have an instance of ValidatorConfigurator
      var validatorConfigurator = new ValidatorConfigurator();

      // Apply the settings to the instance of ValidatorConfigurator
      applyConfiguration(validatorConfigurator);

      // Let the Configurator create a Validator
      return validatorConfigurator.CreateValidator();
   }
}

Create a validator in the Configurator

In the factory above the Create() method of the ValidatorConfigurator was called. Let's write the code for that method:


internal IValidator CreateValidator()
{
   IValidator validator = new ThisValidator();
   validator.Name = this._name;

   return validator;
}

Conclusion

If we run this code:

var validator = ValidatorFactory.New(x=>x.HasName("BestValidatorEver"));

We get an instance of ThisValidator with the name BestValidatorEver. It's obvious that we need to expand the code so that you can choose between ThisValidator or ThatValidator. But that isn't to hard now, right?