FromAsync Begin接收冻结的WinForm

Question

It works great in console application but when I create WinForm, it freezes my form.

I actually know, why it happens:

public static Task<int> ReceiveAsync(this Socket socket, byte[] buffer, int offset, int size, SocketFlags flags = SocketFlags.None)
{
    if (socket == null) throw new Exception("Socket is null.");
        var tcs = new TaskCompletionSource<int>(socket);
        socket.BeginReceive(buffer, offset, size, flags, iar =>
        {
            var t = (TaskCompletionSource<int>)iar.AsyncState;
            var s = (Socket)t.Task.AsyncState;
            try { t.SetResult(s.EndReceive(iar)); }
            catch (Exception exc) { t.SetException(exc); }
        }, tcs);
        return tcs.Task;
    }

while ((byteRead = ReceiveAsync(socket, buffer, 0, buffer.Length, SocketFlags.None).Result) > 0)
{
   lock (buffer)
   {
       try
       {
          byte[] dBuffer = decompressor.Decompress(buffer);
          lock (dBuffer)
          {
              string receivedData = Encoding.UTF8.GetString(dBuffer);
              OnRead(receivedData, byteRead);
          }
       }
       catch (Exception ex)
       {
          Client.Base.Log.Save(ex);
          socket.Shutdown(SocketShutdown.Both);
       }
   }
}

I think, starting the ReceiveAsync-Task method in seperate thread is not an good idea.

Can I use the FormAsync without while loop like Async-Methods (BeginXXX, EndXXX)?

Thanks in advance!

Answer 1

Looks like you need to call your second code snippet in separate thread. Otherwise second snippet will simply force asynchronous calls from first snippet to work synchronously (and that is what makes your WindowsForms application to hang - just invoke whole second part of code that You posted in separate thread and it will work ok).

Edit

To avoid hanging of application it is possible to slightly change definition of functions that you use - as listed below:

    // Is not changed
    public static Task<int> ReceiveAsync(this Socket socket, byte[] buffer, int offset, int size, SocketFlags flags = SocketFlags.None)
    {

        if (socket == null) throw new Exception("Socket is null.");

        var tcs = new TaskCompletionSource<int>(socket);
        socket.BeginReceive(buffer, offset, size, flags, iar =>
        {
            var t = (TaskCompletionSource<int>)iar.AsyncState;
            var s = (Socket)t.Task.AsyncState;
            try { t.SetResult(s.EndReceive(iar)); }
            catch (Exception exc) { t.SetException(exc); }
        }, tcs);
        return tcs.Task;
    }

    // Moved to new function
    public void PerformRead()
    {
        while ((byteRead = ReceiveAsync(socket, buffer, 0, buffer.Length, SocketFlags.None).Result) > 0)
        {
           lock (buffer)
           {
               try
               {
                  byte[] dBuffer = decompressor.Decompress(buffer);
                  lock (dBuffer)
                  {
                      string receivedData = Encoding.UTF8.GetString(dBuffer);
                      OnRead(receivedData, byteRead);
                  }
               }
               catch (Exception ex)
               {
                  Client.Base.Log.Save(ex);
                  socket.Shutdown(SocketShutdown.Both);
               }
           }
        }
    }

then, when you invoke reading socket in a following way, your application will work smoothly (without delays):

// Invokes reading of socket in separate thread
Thread readSocketThread = new Thread(this.PerformRead);
readSocketThread.Start();

Note: You will have to convey data that was read to your windows form controls in some way (for example through some fields or properties or accessing form's fields directly from thread that reads socket).