WebRequest 对象的使用

调用格式：

            string url = "http://localhost:26314/HttpPost.ashx?";
            string postDate = "userid=1&username=李四";
            HttpPost(url, postDate);

c#代码：

        /// <summary>
        /// Post请求
        /// </summary>
        /// <param name="uri">请求的地址：</param>
        /// <param name="postData">参数</param>
        /// <returns></returns>
        string HttpPost(string uri, string postData)
        {
            WebRequest webRequest = WebRequest.Create(uri);
            webRequest.ContentType = "application/x-www-form-urlencoded"; // 设置请求的参数形式
            webRequest.Method = "POST";
            byte[] bytes = Encoding.UTF8.GetBytes(postData); //指定编码格式

            webRequest.ContentLength = bytes.Length; // 设置请求参数的长度.

            Stream inStream = null;
            try
            {
                inStream = webRequest.GetRequestStream(); //取得发向服务器的流
                inStream.Write(bytes, 0, bytes.Length);  //发送
            }
            catch (WebException ex)
            {
                return ex.Message.ToString();
            }
            finally
            {
                if (inStream != null)
                {
                    inStream.Close();
                }
            }

            StreamReader readStream = null;
            try
            {
                WebResponse webResponse = webRequest.GetResponse(); // 等待返回结果
                if (webResponse == null)
                { 
                    return null;
                }
                 readStream = new StreamReader(webResponse.GetResponseStream(), System.Text.Encoding.UTF8);
                return readStream.ReadToEnd().Trim();
            }
            catch (WebException ex)
            {
                return ex.Message.ToString();
            }

            finally
            {
                if (readStream != null)
                {
                    readStream.Close();
                }
            }
        }