public static string MyUploader (string strFileToUpload, string strUrl， Action<double, double> uploading) {
    string strFileFormName = "file";
    Uri oUri = new Uri (strUrl);
    string strBoundary = "----------" + DateTime.Now.Ticks.ToString ("x");
    // The trailing boundary
    string byte[] boundaryBytes = Encoding.ASCII.GetBytes ("\r\n--" + strBoundary + "--\r\n");
    //**注意此处的 strBoundary后的换行前加上--，不然会异常** 
    // The post message header 
    StringBuilder sb = new StringBuilder ();
    sb.Append ("--");
    sb.Append (strBoundary);
    sb.Append ("\r\n");
    sb.Append ("Content-Disposition: form-data; name=\"");
    sb.Append (strFileFormName);
    sb.Append ("\"; filename=\"");
    sb.Append (Path.GetFileName (strFileToUpload));
    sb.Append ("\"");
    sb.Append ("\r\n");
    sb.Append ("Content-Type: ");
    sb.Append ("application/octet-stream");
    sb.Append ("\r\n");
    sb.Append ("\r\n");
    string strPostHeader = sb.ToString ();
    byte[] postHeaderBytes = Encoding.UTF8.GetBytes (strPostHeader);
    // The WebRequest 
    HttpWebRequest oWebrequest = (HttpWebRequest) WebRequest.Create (oUri);
    oWebrequest.ContentType = "multipart/form-data; boundary=" + strBoundary;
    oWebrequest.Method = "POST";
    // This is important, otherwise the whole file will be read to memory anyway... 
    oWebrequest.AllowWriteStreamBuffering = false;
    // Get a FileStream and set the final properties of the WebRequest
    FileStream oFileStream = new FileStream (strFileToUpload, FileMode.Open, FileAccess.Read);
    long length = postHeaderBytes.Length + oFileStream.Length + boundaryBytes.Length;
    oWebrequest.ContentLength = length;
    Stream oRequestStream = oWebrequest.GetRequestStream ();
    // Write the post header 
    oRequestStream.Write (postHeaderBytes, 0, postHeaderBytes.Length);
    // Stream the file contents in small pieces (4096 bytes, max).
    byte[] buffer = new Byte[checked ((uint) Math.Min (4096, (int) oFileStream.Length))];
    int bytesRead = 0;
    double size = 0;
    while ((bytesRead = oFileStream.Read (buffer, 0, buffer.Length)) != 0) { oRequestStream.Write (buffer, 0, bytesRead); size += bytesRead; if (uploading != null) uploading (length, size); }
    oFileStream.Close ();
    // Add the trailing boundary 
    oRequestStream.Write (boundaryBytes, 0, boundaryBytes.Length);
    WebResponse oWResponse = oWebrequest.GetResponse ();
    Stream s = oWResponse.GetResponseStream ();
    StreamReader sr = new StreamReader (s);
    String sReturnString = sr.ReadToEnd ();
    // Clean up 
    oFileStream.Close ();
    oRequestStream.Close ();
    s.Close ();
    sr.Close ();
    return sReturnString;
}

//文件流：读取
FileStream fileStream = File.Open(@"D:\test.txt", FileMode.Open);//初始化文件流
byte[] array = new byte[fileStream.Length];//初始化字节数组，用来暂存读取到的字节
fileStream.Read(array, 0, array.Length);//读取流中数据，写入到字节数组中
fileStream.Close(); //关闭流
string str = Encoding.Default.GetString(array);//将字节数组内容转化为字符串
Response.Write(str);

//文件流：写入
FileStream fileStream = File.Open(@"D:\test.txt",FileMode.Append);//初始化文件流
byte[] array = Encoding.Default.GetBytes("哈哈123abc");//给字节数组赋值
fileStream.Write(array, 0, array.Length);//将字节数组写入文件流
fileStream.Close();//关闭流

TcpListener lis=new TcpListener(5000); //服务器监听
lis.Start();//启动
Socket sock=lis.AcceptSocket();//阻塞，直到有客户端连接

NetworkStream networkStream = new NetworkStream(sock);//得到Socket中的流
if (netStream.DataAvailable)   //如果客户端发送了消息
{
   byte[] data = new byte[1024];   //定义一个字节数组，用来存放接收的数据
   int len = netStream.Read(data, 0, data.Length);  //从位置开始，读取到字节数组末尾
   string line = Encoding.Default.GetString(data, 0, len);  //把收到的字节转换为字符串
}

TcpClient client = new TcpClient();//客户端tcp对象
client.Connect("127.0.0.1", 5000);//连接服务器
NetworkStream myStream = client.GetStream();//得到网络流
                
byte[] data = Encoding.Default.GetBytes("Hi，你好");  //首先把输入的字符串消息转换为字节
myStream .Write(data, 0, data.Length);  //向myStream 里写入数据
myStream .Flush();  //刷新流中的数据
myStream .Close();

string str = "Hi!你好！";
byte[] array = Encoding.UTF8.GetBytes(str);//将字符串转化为字节数组
MemoryStream memory = new MemoryStream(array);//初始化MemoryStream类
byte[] arrayNew = memory.ToArray();//将内存中的数据转换为字节数组
string strNew = Encoding.UTF8.GetString(arrayNew);//将字节数组转换为字符串

//StreamReader 读取
StreamReader reader = new StreamReader(@"D:\test.txt",Encoding.Default);//初始化读取 设置编码格式，否则中文会乱码
string readStr = reader.ReadLine();//从流中读取一行  reader.ReadToEnd()读取全部
reader.Close();//关闭流

//StreamWriter 写入
StreamWriter writer = new StreamWriter(@"D:\test1.txt");//初始化写入
writer.WriteLine("Hi 你好123");//写入一行
writer.Close();

//TextReader/Writer读写
TextReader textReader = new StringReader("Hi 你好");//初始化读取流
TextWriter textWriter = new StringWriter();//初始化写入流

char[] c=new char[4096];
int chars = 0;
while ((chars = textReader.Read(c, 0, 4096)) > 0)//把流中数据写入到字符数组中 读取流中数据
{
   textWriter.Write(c, 0, 4096);//从字符数组中读取流
}

string str= textWriter.ToString();//将流中数据写到字符串中
textReader.Close();//关闭流
textWriter.Close();