Question

As the questions states. I am unable to send List<T> over WCF. I cannot understand why and I have been searching high and low over the internet for the past week without any concrete answers. I keep getting a SocketException: An existing connection was forcibly closed by the remote host. However, if I call a method that only returns a string, it works without problems.

I am hosting my WCF on IIS Express 7.5. I can confirm that I can access my service via my browser or other devices on my local network via my machine’s IP.

If it’s of any help, I am actually following this tutorial:
http://www.c-sharpcorner.com/uploadfile/urmimalapal/creating-a-windows-phone-7-application-consuming-data-using-a-wcf-service/

When I attempt to call FindEmployee, I get that error. I have also created another method that simply returns a string and calling it works fine. No errors. I have tried it on my WP7 emulator, WCF Test Client and WCFStorm and they all exhibit the same problem with List<T> trying to be returned and string being returned with no problems. I have also confirmed the list is being populated properly when my Linq statement hits the breakpoint. It’s definitely WCF refusing to send my List<T>.

Edit:
This is the XML reply I’m getting from WCFStorm when I attempt to call a method that throws a List<T>.

<FindVendor>
  <MethodParameters>
    <SocketException>
      <ErrorCode>10054</ErrorCode>
      <Message>An existing connection was forcibly closed by the remote host</Message>
      <SocketErrorCode>ConnectionReset</SocketErrorCode>
      <NativeErrorCode>10054</NativeErrorCode>
      <Data>
        <KeysAndValues attr0="KeyValuePairArray" isNull="false" />
      </Data>
      <InnerException isNull="true" />
      <TargetSite>Int32 Read(Byte[], Int32, Int32)</TargetSite>
      <StackTrace>at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)</StackTrace>
      <HelpLink isNull="true" />
      <Source>System</Source>
    </SocketException>
  </MethodParameters>
</FindVendor>

Answer 1

I haven’t bothered to download any sample code associated with the tutorial, but I notice the MyEmployee entity is not defined in the tutorial. You should ensure that it is marked with the [Serializable] attribute like so:

[Serializable]
public class MyEmployee
{
    public int Property1 { get; set; } // etc
} 

There is also the possiblity that you will have to declare KnownTypes to the serialiser, depending on what you are doing – you should post the piece of code, and maybe turn on WCF logging to get you a better error message.