asp.net后台发送HTTP请求

一、文件流方式（转自：http://blog.****.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, , 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.****.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));
        }
    }
}