System.Net.Mail.SmtpConnection.BeginFlush C# (CSharp) Method

        internal IAsyncResult BeginFlush(AsyncCallback callback, object state)
        {
            return _networkStream.BeginWrite(_bufferBuilder.GetBuffer(), 0, _bufferBuilder.Length, callback, state);
        }

        internal static IAsyncResult BeginSend(SmtpConnection conn, AsyncCallback callback, object state)
        {
            MultiAsyncResult multiResult = new MultiAsyncResult(conn, callback, state);

            multiResult.Enter();
            IAsyncResult writeResult = conn.BeginFlush(s_onWrite, multiResult);

            if (writeResult.CompletedSynchronously)
            {
                conn.EndFlush(writeResult);
                multiResult.Leave();
            }
            SmtpReplyReader reader = conn.Reader.GetNextReplyReader();

            multiResult.Enter();

            //this actually does a read on the stream.
            IAsyncResult result = reader.BeginReadLine(s_onReadLine, multiResult);

            if (result.CompletedSynchronously)
            {
                LineInfo info = reader.EndReadLine(result);
                if (!(multiResult.Result is Exception))
                {
                    multiResult.Result = info;
                }
                multiResult.Leave();
            }
            multiResult.CompleteSequence();
            return(multiResult);
        }