C# POST 发送XML（返回string中可能出现中文乱码问题）

	/// <summary>
        /// C#  POST 发送XML
        /// </summary>
        /// <param name="url">目标Url</param>
        /// <param name="strPost">要Post的字符串(数据)</param>
        /// <returns>服务器响应</returns>
        private string PostXml(string url, string strPost)
        {
            string result = string.Empty;
            //Our postvars
            //ASCIIEncoding.ASCII.GetBytes（string str）
            //就是把字符串str按照简体中文(ASCIIEncoding.ASCII)的编码方式，
            //编码成 Bytes类型的字节流数组;
           // 要注意的这是这个编码方式，还有内容的Xml内容的编码方式,如果没有注意对应会出现文末的错误
            byte[] buffer = Encoding.UTF8.GetBytes(strPost);
            StreamWriter myWriter = null;
            //根据url创建HttpWebRequest对象
            //Initialisation, we use localhost, change if appliable
            HttpWebRequest objRequest = (HttpWebRequest)WebRequest.Create(url);
            //Our method is post, otherwise the buffer (postvars) would be useless
            objRequest.Method = "POST";
            //The length of the buffer (postvars) is used as contentlength.
            //Set the content length of the string being posted.
            objRequest.ContentLength = buffer.Length;
            //We use form contentType, for the postvars.
            //Set the content type of the data being posted.
            objRequest.ContentType = "text/xml";//提交xml 
            //objRequest.ContentType = "application/x-www-form-urlencoded";//提交表单
            try
            {
                //We open a stream for writing the postvars
                myWriter = new StreamWriter(objRequest.GetRequestStream());
                //Now we write, and afterwards, we close. Closing is always important!
                myWriter.Write(strPost);
            }
            catch (Exception e)
            {
                return e.Message;
            }
            finally
            {
                myWriter.Close();
            }
	    //读取服务器返回信息
            //Get the response handle, we have no true response yet!
            HttpWebResponse objResponse = (HttpWebResponse)objRequest.GetResponse();
            //using作为语句，用于定义一个范围，在此范围的末尾将释放对象
            using (StreamReader sr = new StreamReader(objResponse.GetResponseStream()))
            {
                //ReadToEnd适用于小文件的读取，一次性的返回整个文件
                result = sr.ReadToEnd();
                sr.Close();
            }
            return result;
        }

背景: