Does WCF support Multi-threading itself?

Question

I developed a proof of concept application that query if WCF support multi-threading.

Now, all what I did is creating a service contract marked with

 [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single,
                  ConcurrencyMode = ConcurrencyMode.Multiple, 
                  UseSynchronizationContext = true)]

with two operations to get fixed texts. The first method do a Thread.Sleep for 8 seconds to make the response delayed and the other one return data directly.

The issue I faced was when I run two instances of client application and request from the first client the method with delay and request the other method from the second client, I got a sequential response.

How can I get the response from the service while the service is busy with another request?

 namespace WCFSyncService
 {
    [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)], 
                 ConcurrencyMode = ConcurrencyMode.Multiple, 
                 UseSynchronizationContext = true)]

    public class ServiceImplementation : IService

    {
        public ServiceImplementation()
        {
        }

        #region IService Members

        public string GetDelayedResponse()
        {
            System.Threading.Thread.Sleep(8000);
            return "Slow";
        }

        public string GetDirectResponse()
        {
            return "Fast";
        }

        #endregion
    }
}

I need to call the methods GetDelayedResponse and GetDirectResponse at the same time and get the "fast" text before the 8 seconds ends.

---

Hosting application code

namespace ServiceHostApplication
{
    public partial class frmMain : Form
    {
        private WCFSessionServer.IService oService;

        public frmMain()
        {
            InitializeComponent();
        }

        private void btnStartService_Click(object sender, EventArgs e)
        {
            ServiceHost objSvcHost;

            oService = new WCFSessionServer.ServiceImplementation();
         objSvcHost = new ServiceHost( typeof(WCFSessionServer.ServiceImplementation));
            objSvcHost.Open();
        }
    }
}

---

Below is the code I implement it to test the case:

Server side classes,

1. Service's interface

   namespace WCFSessionServer
   {
       [ServiceContract]
       public interface IService
   
       {
           [OperationContract]
           string GetDelayedResponse();
   
          [OperationContract]
          string GetDirectResponse();
       }
    }
   

2. Implementation class

   namespace WCFSessionServer
   {
      [ServiceBehavior(
                       InstanceContextMode = InstanceContextMode.PerCall,
                       ConcurrencyMode =   ConcurrencyMode.Multiple,
                       UseSynchronizationContext =  true)]
       public class ServiceImplementation : IService
        {
            public ServiceImplementation()
               {
               }
   
            #region Service Members
            public string GetDelayedResponse()
               {
                System.Threading.Thread.Sleep(8000);
                return "Slow";
               }
   
            public string GetDirectResponse()
            {
                return "Fast";
            }
            #endregion
        }
    }
   

3. Server-side app.config

   <system.serviceModel>
    <services>
     <service 
               behaviorConfiguration = "WCFSessionServer.IService"  
               name = "WCFSessionServer.ServiceImplementation" >
     <endpoint address="http://localhost:2020/SessionService/basic/"
               behaviorConfiguration="WCFSessionServer.IService"
               binding="basicHttpBinding"
               name="BasicHttpBinding_IService"
               bindingName="myBasicHttpBinding"
               contract="WCFSessionServer.IService" />
     <endpoint address="mex"
               binding="mexHttpBinding"
               contract="IMetadataExchange" />
     <host>
      <baseAddresses>
        <add baseAddress="http://localhost:2020/SessionService/" />
      </baseAddresses>
     </host>
   </service>
    </services>
         <behaviors>
         <endpointBehaviors>
          <behavior name="TimeOut">
           <callbackTimeouts transactionTimeout="00:00:02"/>
         </behavior>
        <behavior name="WCFSessionServer.IService" >
          <dataContractSerializer maxItemsInObjectGraph="2147483647" />
        </behavior>
      </endpointBehaviors>
      <serviceBehaviors>
       <behavior name="WCFSessionServer.IService">
          <serviceThrottling    maxConcurrentCalls="10"
                                maxConcurrentSessions="10"
                                maxConcurrentInstances="10"/>
              <dataContractSerializer maxItemsInObjectGraph="2147483647" />
              <serviceMetadata httpGetEnabled="True"/> 
              <serviceDebug includeExceptionDetailInFaults="True" />
            </behavior>
          </serviceBehaviors>
        </behaviors>
      </system.serviceModel>
   

Client-side app.config

    <system.serviceModel>
          <bindings>
              <basicHttpBinding>
                  <binding name="BasicHttpBinding_IService"
                           closeTimeout="00:01:00"
                           openTimeout="00:01:00"
                           receiveTimeout="00:10:00"
                           sendTimeout="00:01:00"
                           allowCookies="false"
                           bypassProxyOnLocal="false"
                           hostNameComparisonMode="StrongWildcard"
                           maxBufferSize="65536"
                           maxBufferPoolSize="524288"
                           maxReceivedMessageSize="65536"
                           messageEncoding="Text"
                           textEncoding="utf-8"
                           transferMode="Buffered"
                           useDefaultWebProxy="true">
                           <readerQuotas maxDepth="32"
                                         maxStringContentLength="8192"
                                         maxArrayLength="16384"
                                         maxBytesPerRead="4096"
                                         maxNameTableCharCount="16384" />
                    <security mode="None">
                    <transport
                              clientCredentialType="None"
                              proxyCredentialType="None"
                              realm="" />
                    <message 
                             clientCredentialType="UserName"
                             algorithmSuite="Default" />
                </security>
            </binding>
        </basicHttpBinding>
    </bindings>
    <client>
        <endpoint address="http://localhost:2020/SessionService/basic/"
                  binding="basicHttpBinding"
                  bindingConfiguration="BasicHttpBinding_IService"
                  contract="SessionServiceProxy.IService"
                  name="BasicHttpBinding_IService" />
    </client>
</system.serviceModel>

Answer 1

Try to change the value of the attribute

UseSynchronizationContext=false