C#：一个增强的NetworkStream（二）写入

using System;
using System.Net.Sockets;
using System.Text;
using System.Threading;

namespace Splash.Net.Sockets
{
    /// <summary>
    /// 异步写状态对象
    /// </summary>
    internal class AsyncWriteStateObject
    {
        public ManualResetEvent eventDone;
        public NetworkStream stream;
        public Exception exception;
    }

    /// <summary>
    /// 实现TcpClient的异步发送
    /// </summary>
    public partial class NetworkStreamPlus
    {
        /// <summary>
        /// 异步发送
        /// </summary>
        /// <param name="buffer">字节数组</param>
        /// <param name="offset">起始偏移量</param>
        /// <param name="size">字节数</param>
        public void Write(Byte[] buffer, Int32 offset, Int32 size)
        {
            // 用户定义对象
            AsyncWriteStateObject State = new AsyncWriteStateObject
            {   // 将事件状态设置为非终止状态，导致线程阻止
                eventDone = new ManualResetEvent(false),
                stream = Stream,
                exception = null,
            };
            
            Byte[] BytesArray;
            if (String.IsNullOrEmpty(_secretKey))
            {   // 在数据前插入长度信息
                Int32 Length = size + 4;    // 加入4字节长度信息后的总长度
                BytesArray = new Byte[Length];
                Array.Copy(BitConverter.GetBytes(Length), BytesArray, 4);
                Array.Copy(buffer, offset, BytesArray, 4, size);
            }
            else
            {   // 数据加密
                Byte[] Cipher = Encrypt(buffer, offset, size); 
                
                // 在数据前插入长度信息
                Int32 Length = Cipher.Length + 4;
                BytesArray = new Byte[Length];
                Array.Copy(BitConverter.GetBytes(Length), BytesArray, 4);
                Array.Copy(Cipher, 0, BytesArray, 4, Cipher.Length);
            }        

            // 写入加长度信息头的数据
            Stream.BeginWrite(BytesArray, 0, BytesArray.Length, new AsyncCallback(AsyncWriteCallback), State);

            // 等待操作完成信号
            if (State.eventDone.WaitOne(Stream.WriteTimeout, false))
            {   // 接收到信号
                if (State.exception != null) throw State.exception;
            }
            else
            {   // 超时异常
                throw new TimeoutException();
            }
        }

        /// <summary>
        /// 异步发送
        /// </summary>
        /// <param name="data">字节数组</param>
        public void Write(Byte[] data)
        {
            Write(data, 0, data.Length);
        }

        /// <summary>
        /// 异步发送
        /// </summary>
        /// <param name="command">字符串</param>
        /// <param name="codePage">代码页</param>
        /// <remarks>
        /// 代码页：
        ///     936：简体中文GB2312
        ///     54936：简体中文GB18030
        ///     950：繁体中文BIG5
        ///     1252：西欧字符CP1252
        ///     65001：UTF-8编码
        /// </remarks>
        public void Write(String command, Int32 codePage = 65001)
        {
            Write(Encoding.GetEncoding(codePage).GetBytes(command));
        }

        /// <summary>
        /// 异步写入回调函数
        /// </summary>
        /// <param name="ar">异步操作结果</param>
        private static void AsyncWriteCallback(IAsyncResult ar)
        {
            AsyncWriteStateObject State = ar.AsyncState as AsyncWriteStateObject;
            try
            {   // 异步写入结束
                State.stream.EndWrite(ar);
            }

            catch (Exception e)
            {   // 异步连接异常
                State.exception = e;
            }

            finally
            {   // 将事件状态设置为终止状态，线程继续
                State.eventDone.Set();
            }
        }
    }
}