asp.net后台发送HTTP请求

一、文件流方式（转自：http://blog.csdn.net/u011511086/article/details/53216330）

/// 发送请求  
        /// </summary>  
        /// <param name="url">请求地址</param>  
        /// <param name="sendData">参数格式 “name=王武&pass=123456”</param>  
        /// <returns></returns>  
        public static string RequestWebAPI(string url, string sendData)  
        {  
            string backMsg = "";  
            try  
            {  
                System.Net.WebRequest httpRquest = System.Net.HttpWebRequest.Create(url);  
                httpRquest.Method = "POST";  
                //这行代码很关键，不设置ContentType将导致后台参数获取不到值  
                httpRquest.ContentType = "application/x-www-form-urlencoded;charset=UTF-8";  
                byte[] dataArray = System.Text.Encoding.UTF8.GetBytes(sendData);  
                //httpRquest.ContentLength = dataArray.Length;  
                System.IO.Stream requestStream = null;  
                if (string.IsNullOrWhiteSpace(sendData) == false)  
                {  
                    requestStream = httpRquest.GetRequestStream();  
                    requestStream.Write(dataArray, 0, dataArray.Length);  
                    requestStream.Close();  
                }  
                System.Net.WebResponse response = httpRquest.GetResponse();  
                System.IO.Stream responseStream = response.GetResponseStream();  
                System.IO.StreamReader reader = new System.IO.StreamReader(responseStream, System.Text.Encoding.UTF8);  
                backMsg = reader.ReadToEnd();  
  
  
                reader.Close();  
                reader.Dispose();  
  
  
                requestStream.Dispose();  
                responseStream.Close();  
                responseStream.Dispose();  
            }  
            catch (Exception)  
            {  
                throw;  
            }  
            return backMsg;  
        }  

二、HttpClient方式（转自：http://blog.csdn.net/qianmenfei/article/details/37974767）

1、通用http类

using System;  
using System.Globalization;  
using System.Net;  
using System.Text;  
  
namespace Test  
{  
    public class HttpCommon  
    {  
        /// <summary>  
        /// Http同步Get同步请求  
        /// </summary>  
        /// <param name="url">Url地址</param>  
        /// <param name="encode">编码(默认UTF8)</param>  
        /// <returns></returns>  
        public static string HttpGet(string url, Encoding encode = null)  
        {  
            string result;  
  
            try  
            {  
                var webClient = new WebClient { Encoding = Encoding.UTF8 };  
  
                if (encode != null)  
                    webClient.Encoding = encode;  
  
                result = webClient.DownloadString(url);  
            }  
            catch (Exception ex)  
            {  
                result = ex.Message;  
            }  
  
            return result;  
        }  
  
        /// <summary>  
        /// Http同步Get异步请求  
        /// </summary>  
        /// <param name="url">Url地址</param>  
        /// <param name="callBackDownStringCompleted">回调事件</param>  
        /// <param name="encode">编码(默认UTF8)</param>  
        public static void HttpGetAsync(string url,  
            DownloadStringCompletedEventHandler callBackDownStringCompleted = null, Encoding encode = null)  
        {  
            var webClient = new WebClient { Encoding = Encoding.UTF8 };  
  
            if (encode != null)  
                webClient.Encoding = encode;  
  
            if (callBackDownStringCompleted != null)  
                webClient.DownloadStringCompleted += callBackDownStringCompleted;  
  
            webClient.DownloadStringAsync(new Uri(url));  
        }  
  
        /// <summary>  
        ///  Http同步Post同步请求  
        /// </summary>  
        /// <param name="url">Url地址</param>  
        /// <param name="postStr">请求Url数据</param>  
        /// <param name="encode">编码(默认UTF8)</param>  
        /// <returns></returns>  
        public static string HttpPost(string url, string postStr = "", Encoding encode = null)  
        {  
            string result;  
  
            try  
            {  
                var webClient = new WebClient { Encoding = Encoding.UTF8 };  
  
                if (encode != null)  
                    webClient.Encoding = encode;  
  
                var sendData = Encoding.GetEncoding("GB2312").GetBytes(postStr);  
  
                webClient.Headers.Add("Content-Type", "application/x-www-form-urlencoded");  
                webClient.Headers.Add("ContentLength", sendData.Length.ToString(CultureInfo.InvariantCulture));  
  
                var readData = webClient.UploadData(url, "POST", sendData);  
  
                result = Encoding.GetEncoding("GB2312").GetString(readData);  
  
            }  
            catch (Exception ex)  
            {  
                result = ex.Message;  
            }  
  
            return result;  
        }  
  
        /// <summary>  
        /// Http同步Post异步请求  
        /// </summary>  
        /// <param name="url">Url地址</param>  
        /// <param name="postStr">请求Url数据</param>  
        /// <param name="callBackUploadDataCompleted">回调事件</param>  
        /// <param name="encode"></param>  
        public static void HttpPostAsync(string url, string postStr = "",  
            UploadDataCompletedEventHandler callBackUploadDataCompleted = null, Encoding encode = null)  
        {  
            var webClient = new WebClient { Encoding = Encoding.UTF8 };  
  
            if (encode != null)  
                webClient.Encoding = encode;  
  
            var sendData = Encoding.GetEncoding("GB2312").GetBytes(postStr);  
  
            webClient.Headers.Add("Content-Type", "application/x-www-form-urlencoded");  
            webClient.Headers.Add("ContentLength", sendData.Length.ToString(CultureInfo.InvariantCulture));  
  
            if (callBackUploadDataCompleted != null)  
                webClient.UploadDataCompleted += callBackUploadDataCompleted;  
  
            webClient.UploadDataAsync(new Uri(url), "POST", sendData);  
        }  
    }  
}  

2、调用类

using System;  
using System.Net;  
using System.Text;  
using System.Web.UI;  
  
namespace Test  
{  
    public partial class WebForm3 : Page  
    {  
        protected void Page_Load(object sender, EventArgs e)  
        {  
            Response.Write(HttpCommon.HttpGet("http://localhost:14954/WebForm4.aspx"));                          //Get同步  
            HttpCommon.HttpGetAsync("http://localhost:14954/WebForm4.aspx");                                     //Get异步  
            HttpCommon.HttpGetAsync("http://localhost:14954/WebForm4.aspx", DownStringCompleted);                //Get异步回调  
  
            Response.Write(HttpCommon.HttpPost("http://localhost:14954/WebForm4.aspx", "post=POST"));            //Post同步  
            HttpCommon.HttpPostAsync("http://localhost:14954/WebForm4.aspx", "post=POST");                       //Post异步  
            HttpCommon.HttpPostAsync("http://localhost:14954/WebForm4.aspx", "post=POST", UploadDataCompleted);  //Post异步回调  
        }  
  
        private void DownStringCompleted(object sender, DownloadStringCompletedEventArgs e)  
        {  
            Response.Write(e.Result);  
        }  
  
        private void UploadDataCompleted(object sender, UploadDataCompletedEventArgs e)  
        {  
            Response.Write(Encoding.GetEncoding("GB2312").GetString(e.Result));  
        }  
    }  
}