HttpWebRequest以UTF-8编码写入内容时发生“Bytes to be written to the stream exceed the Content-Length bytes size specified.”错误

出错代码如下：

  
    

   
     
   
     request.ContentLength 
   
     =
   
      Encoding.UTF8.GetByteCount(content); var writer 
   
     =
   
      
   
     new
   
      StreamWriter(request.GetRequestStream(), Encoding.UTF8); writer.Write(content); writer.Flush(); writer.Close();
  
    

原因是直接使用Encoding.UTF8，在StreamWriter中使用这个Encoding会在流的开头写入byte order mark. 解决方法是改用new UTF8Encoding(false)来构造不写入byte order mark的Encoding.