I made a simple WCF client and checked the "create asynchronous methods" box.. what do these methods do?

Question

I created a server and generated my client as an asynchronous one.

So when I connect, I do so asynchronously. That's fine.

I have a method on my client (a callback method) that receives data from the server. The server sends this data using an asychronous method too.

To receive this data on my client, I expected to have ONLY a method like this one it generated for me:

public void SendToClient(string dataToSend)
{
}

Although it has a bizarre name, this is the method that I expected - it is called when data is received.

However it has also generated these methods:

public IAsyncResult BeginSendToClient(string dataToSend, AsyncCallback callback, object asyncState)
{
        throw new NotImplementedException();
}

public void EndSendToClient(IAsyncResult result)
{
    throw new NotImplementedException();
}

I don't know how to use them. It's like an asynchronous receive, or something. How would I use them to receive data?

Answer 1

Generally you don't want callback contract operations to be asynchronous. You would be forced to implement the asynchronous programming model which is difficult to get right, and unnecessary in this case.

You should be able to get away with not implementing the asynchronous versions on the server side and just fill in the synchronous one. On the client side (the caller of the async callback contract), WCF should do the right thing, and behind the scenes your synchronous version will be called when the data arrives on your end.

As a sidenote, it seems that a customer reported this as a bug, but it looks like it did not get addressed: http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=293507