Facebook.CombinationStream.BeginRead C# (CSharp) Method

        public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, object state)
        {
            CombinationStreamAsyncResult asyncResult = new CombinationStreamAsyncResult(state);
            if (count > 0)
            {
                int buffPostion = offset;

                AsyncCallback rc = null;
                rc = readresult =>
                         {
                             try
                             {
                                 int bytesRead = _currentStream.EndRead(readresult);
                                 asyncResult.BytesRead += bytesRead;
                                 buffPostion += bytesRead;
                                 _postion += bytesRead;

                                 if (bytesRead <= count)
                                     count -= bytesRead;

                                 if (count > 0)
                                 {
                                     if (_currentStreamIndex >= _streams.Count)
                                     {
                                         // done
                                         asyncResult.CompletedSynchronously = false;
                                         asyncResult.SetAsyncWaitHandle();
                                         asyncResult.IsCompleted = true;
                                         callback(asyncResult);
                                     }
                                     else
                                     {
                                         _currentStream = _streams[_currentStreamIndex++];
                                         _currentStream.BeginRead(buffer, buffPostion, count, rc, readresult.AsyncState);
                                     }
                                 }
                                 else
                                 {
                                     // done
                                     asyncResult.CompletedSynchronously = false;
                                     asyncResult.SetAsyncWaitHandle();
                                     asyncResult.IsCompleted = true;
                                     callback(asyncResult);
                                 }
                             }
                             catch (Exception ex)
                             {
                                 // done
                                 asyncResult.Exception = ex;
                                 asyncResult.CompletedSynchronously = false;
                                 asyncResult.SetAsyncWaitHandle();
                                 asyncResult.IsCompleted = true;
                                 callback(asyncResult);
                             }
                         };
                _currentStream.BeginRead(buffer, buffPostion, count, rc, state);
            }
            else
            {
                // done
                asyncResult.CompletedSynchronously = true;
                asyncResult.SetAsyncWaitHandle();
                asyncResult.IsCompleted = true;
                callback(asyncResult);
            }

            return asyncResult;
        }