System.Diagnostics.AsyncStreamReader.ReadBuffer C# (CSharp) Method

        private void ReadBuffer(IAsyncResult ar) {
            
            int byteLen;
            
            try {
                byteLen = stream.EndRead(ar);
            }
            catch (IOException ) {
                // We should ideally consume errors from operations getting cancelled
                // so that we don't crash the unsuspecting parent with an unhandled exc. 
                // This seems to come in 2 forms of exceptions (depending on platform and scenario), 
                // namely OperationCanceledException and IOException (for errorcode that we don't 
                // map explicitly).   
                byteLen = 0; // Treat this as EOF
            }
            catch (OperationCanceledException ) {
                // We should consume any OperationCanceledException from child read here  
                // so that we don't crash the parent with an unhandled exc
                byteLen = 0; // Treat this as EOF
            }
                
            if (byteLen == 0) { 
                // We're at EOF, we won't call this function again from here on.
                lock(messageQueue) {
                    if( sb.Length != 0) {
                        messageQueue.Enqueue(sb.ToString());
                        sb.Length = 0;
                    }
                    messageQueue.Enqueue(null);
                }

                try {
                    // UserCallback could throw, we should still set the eofEvent 
                    FlushMessageQueue();
                }
                finally {
                    eofEvent.Set();
                }
            } else {
                int charLen = decoder.GetChars(byteBuffer, 0, byteLen, charBuffer, 0);
                sb.Append(charBuffer, 0, charLen);
                GetLinesFromStringBuilder();
                stream.BeginRead(byteBuffer, 0 , byteBuffer.Length,  new AsyncCallback(ReadBuffer), null);
            }
        }