微信开发者-主动请求-准备工作-（1）发送get、post请求，上传文件（C#）

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Web;

/// <summary>
/// RequestHelper 的摘要说明
/// </summary>
public class RequestHelper
{
    //发送get请求
    public static string sendGet(string url)
    {
        MemoryStream content = new MemoryStream();
        // 对url发起一个Web请求
        HttpWebRequest webRequest = WebRequest.Create(url) as HttpWebRequest;
        if (webRequest != null)
        {
            // 返回回复结果
            using (WebResponse response = webRequest.GetResponse())
            {
                using (Stream responseStream = response.GetResponseStream())
                {
                    using (StreamReader reader = new StreamReader(responseStream))
                    {
                        return reader.ReadToEnd();
                    }
                }
            }
        }
        return "";
    }
    //发送post请求
    public static string sendPost(string url, string data)
    {
        HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(url);
        Encoding encoding = Encoding.UTF8;
        string param = data;
        //encoding.GetBytes(postData);
        byte[] bs = encoding.GetBytes(data); //Encoding.ASCII.GetBytes(param);
        string responseData = String.Empty;
        req.Method = "POST";
        req.ContentType = "application/x-www-form-urlencoded";
        req.ContentLength = bs.Length;
        using (Stream reqStream = req.GetRequestStream())
        {
            reqStream.Write(bs, 0, bs.Length);
            reqStream.Close();
        }
        using (HttpWebResponse response = (HttpWebResponse)req.GetResponse())
        {
            using (StreamReader reader = new StreamReader(response.GetResponseStream(), encoding))
            {
                responseData = reader.ReadToEnd().ToString();
                return responseData;
            }
        }
    }
    //上传文件
    public static String uploadFile(String url, byte[] file, String contenttype, String filename)
    {
        byte[] buffer = file;
        string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
        //请求
        WebRequest req = WebRequest.Create(url);
        req.Method = "POST";
        req.ContentType = "multipart/form-data; boundary=" + boundary;
        //组织表单数据
        StringBuilder sb = new StringBuilder();
        sb.Append("--" + boundary + "\r\n");
        sb.Append("Content-Disposition: form-data; name=\"media\"; filename=\"" + filename + "\"; filelength=\"" + buffer.Length + "\"");
        sb.Append("\r\n");
        sb.Append("Content-Type: " + contenttype);
        sb.Append("\r\n\r\n");
        string head = sb.ToString();
        byte[] form_data = Encoding.UTF8.GetBytes(head);

        //结尾
        byte[] foot_data = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");

        //post总长度
        long length = form_data.Length + buffer.Length + foot_data.Length;

        req.ContentLength = length;

        Stream requestStream = req.GetRequestStream();
        //这里要注意一下发送顺序，先发送form_data > buffer > foot_data
        //发送表单参数
        requestStream.Write(form_data, 0, form_data.Length);
        //发送文件内容
        requestStream.Write(buffer, 0, buffer.Length);
        //结尾
        requestStream.Write(foot_data, 0, foot_data.Length);
        requestStream.Flush();
        requestStream.Close();
        //响应
        WebResponse pos = req.GetResponse();
        StreamReader sr = new StreamReader(pos.GetResponseStream(), Encoding.UTF8);
        string result = sr.ReadToEnd().Trim();
        sr.Close();
        sr.Dispose();
        if (pos != null)
        {
            pos.Close();
            pos = null;
        }
        if (req != null)
        {
            req = null;
        }
        return result;
    }

}

以上代码大部分来自网络，未记载出处。

处理过程大概如下：

（1）用HttpWebRequest模拟http请求。

HttpWebRequest webRequest = WebRequest.Create(url) as HttpWebRequest;

（2）用WebResponse 接收返回结果

WebResponse response = webRequest.GetResponse()