//--------------------------------------------string转stream---------------------------------------------
Stream s = new MemoryStream(ASCIIEncoding.Default.GetBytes("Test String"));
//--------------------------------------------stream转string---------------------------------------------
StreamReader readStream = new StreamReader(receiveStream,encode);
string str = readStream.ReadToEnd();
http://blog.youkuaiyun.com/weir75034/archive/2008/12/15/3519235.aspx