Task-based Asynchronous Operation in WCF

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Introduction

Though performance blocking and sluggishness are the tailbacks for any application, we can easily overcome these bottlenecks by using asynchronous programming. But old-style practice for asynchronous programming is not way easy enough to write, debug and maintain. So what is the contemporary approach??

Well, in my view, this is task based asynchronous programming, which is updated in .NET 4.5 through the use of keywords await and async. But what do async and await do? async and await are the way of controlling continuation. When a method uses the async keyword, it means it is an asynchronous method, which might have an await keyword inside, and if it has an await keyword, async will activate it. So, simply async activates the await, from which point, the asynchronous has been started. There is a nice explanation that has been given here.

In WCF, we can also consider an asynchronous operation while the service operation creates a delaying call. There are three ways to implement asynchronous operations:

• Task-based asynchronous
• Event-based asynchronous
• IAsyncResult asynchronous

In this article, I am going to use task-based asynchronous operation since this is the most contemporary strategy.

Okay. Let’s move to the code.

Define and Implement Service

A very simple Service contract such as:

[ServiceContract]
public interface IMessage
{
    [OperationContract]
    Task<string> GetMessages(string msg);
}

With this simple contract, the implementation is just straight forward.

public class MessageService : IMessage
{
   async Task<string> IMessage.GetMessages(string msg)
   {
      var task = Task.Factory.StartNew(() =>
                                     {
                                         Thread.Sleep(10000);
                                         return "Return from Server : " + msg;
                                     });
     return await task.ConfigureAwait(false);
   }
}

Here, the method is marked with the async keyword, which means it might use await keyword inside. It also means that the method will be able to suspend and then resume asynchronously at await points. Moreover, it points the compiler to boost the outcome of the method or any exceptions that may happen into the return type.

Service Hosting

class Program
{
    static void Main(string[] args)
    {
       var svcHost = new ServiceHost(typeof (MessageService));
       Console.WriteLine("Available Endpoints :\n");
       svcHost.Description.Endpoints.ToList().ForEach
        (endpoints=> Console.WriteLine(endpoints.Address.ToString()));
       svcHost.Open();
       Console.ReadLine();
    }
}

Service Configuration

<?xml version="1.0"?>
 <configuration>
     <system.serviceModel>
       <services>
          <service name="Rashim.RND.WCF.Asynchronous.ServiceImplementation.MessageService">
             <host>
                 <baseAddresses>
                     <add baseAddress="net.Tcp://localhost:8732/"/>
                     <add baseAddress="http://localhost:8889/"/>
                 </baseAddresses>
             </host>
             <endpoint address="Tcp" binding="netTcpBinding" 
             contract="Rashim.RND.WCF.Asynchronous.Services.IMessage"/>
             <endpoint address="Http" binding="basicHttpBinding" 
             contract="Rashim.RND.WCF.Asynchronous.Services.IMessage">
                 <identity>
                      <dns value="localhost"/>
                 </identity>
             </endpoint>
             <endpoint address="mex" binding="mexTcpBinding" contract="IMetadataExchange"/>
             <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
          </service>
       </services>
       <behaviors>
          <serviceBehaviors>
             <behavior>
                 <serviceMetadata/>
             </behavior>
          </serviceBehaviors>
       </behaviors>
     </system.serviceModel>
     <startup><supportedRuntime version="v4.0" 
     sku=".NETFramework,Version=v4.5"/></startup>
</configuration>

After configuring the service, we need to configure the client app to consume the service.

Define Client

A simple Console Application (Client):

class Program
 {
    static void Main(string[] args)
    {
       GetResult();
       Console.ReadLine();
    }

    private async static void GetResult()
    {
       var client = new Proxy("BasicHttpBinding_IMessage");
       var task = Task.Factory.StartNew(() => client.GetMessages("Hello"));
       var str = await task;
       str.ContinueWith(e =>
       {
          if (e.IsCompleted)
           {
              Console.WriteLine(str.Result);
           }
       });
      Console.WriteLine("Waiting for the result");
    }
 }

Client Configuration

<?xml version="1.0"?>
 <configuration>
   <system.serviceModel>
     <bindings>
       <basicHttpBinding>
         <binding name="BasicHttpBinding_IMessage" />
       </basicHttpBinding>
     </bindings>
     <client>
       <endpoint address="http://localhost:8889/Http" binding="basicHttpBinding"
          bindingConfiguration="BasicHttpBinding_IMessage" 
          contract="Rashim.RND.WCF.Asynchronous.Services.IMessage"
           name="BasicHttpBinding_IMessage" />
     </client>
   </system.serviceModel>
 </configuration>

Finally, proxy class is given below through which the client will consume the services.

public class Proxy : ClientBase<IMessage>, IMessage
 {
    public Proxy()
    {
    }
    public Proxy(string endpointConfigurationName) :
    base(endpointConfigurationName)
    {
    }
    public Task<string> GetMessages(string msg)
    {
      return Channel.GetMessages(msg);
    }
 }

That’s it. Very easy stuff though.