上传永久素材（图片，视频）

using System.Web.Mvc;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Web;
namespace BoldSeas.WeChat.UI.OpenApi.Controllers
{
    public class HomeController : BaseController
    {
        //
        // GET: /Home/

        public ActionResult Index()
        {
            string localPath = Path.GetFullPath("D:\3.jpg");
            string accessToken = "--";
            string result = UploadVideo.GetUploadVideoResult(accessToken, localPath, "标题", "描述");
            //Response.Write(result);
            return Json(result);
        }
    }





    public static class UploadVideo
    {

        public static string GetUploadVideoResult(string accessToken, string filePath, string title, string introduction)
        {
            var url = string.Format("https://api.weixin.qq.com/cgi-bin/material/add_material?access_token={0}", accessToken);
            var fileDictionary = new Dictionary<string, string>();
            fileDictionary["media"] = filePath;
            fileDictionary["description"] = string.Format("{{"title":"{0}", "introduction":"{1}"}}", title, introduction);

            string returnText = string.Empty;
            Dictionary<string, string> postDataDictionary = null;
            using (MemoryStream ms = new MemoryStream())
            {
                postDataDictionary.FillFormDataStream(ms); //填充formData
                returnText = HttpPost(url, null, ms, fileDictionary, null, null, 1200000);
            }
            return returnText;
        }

        /// <summary>
        /// 填充表单信息的Stream
        /// </summary>
        /// <param name="formData"></param>
        /// <param name="stream"></param>
        public static void FillFormDataStream(this Dictionary<string, string> formData, Stream stream)
        {
            string dataString = GetQueryString(formData);
            var formDataBytes = formData == null ? new byte[0] : Encoding.UTF8.GetBytes(dataString);
            stream.Write(formDataBytes, 0, formDataBytes.Length);
            stream.Seek(0, SeekOrigin.Begin);//设置指针读取位置
        }

        /// <summary>
        /// 组装QueryString的方法
        /// 参数之间用&连接，首位没有符号，如：a=1&b=2&c=3
        /// </summary>
        /// <param name="formData"></param>
        /// <returns></returns>
        public static string GetQueryString(this Dictionary<string, string> formData)
        {
            if (formData == null || formData.Count == 0)
            {
                return "";
            }

            StringBuilder sb = new StringBuilder();

            var i = 0;
            foreach (var kv in formData)
            {
                i++;
                sb.AppendFormat("{0}={1}", kv.Key, kv.Value);
                if (i < formData.Count)
                {
                    sb.Append("&");
                }
            }

            return sb.ToString();
        }

        /// <summary>
        /// 根据完整文件路径获取FileStream
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static FileStream GetFileStream(string fileName)
        {
            FileStream fileStream = null;
            if (!string.IsNullOrEmpty(fileName) && File.Exists(fileName))
            {
                fileStream = new FileStream(fileName, FileMode.Open);
            }
            return fileStream;
        }

        /// <summary>
        /// 使用Post方法获取字符串结果
        /// </summary>
        /// <param name="url"></param>
        /// <param name="cookieContainer"></param>
        /// <param name="postStream"></param>
        /// <param name="fileDictionary">需要上传的文件，Key：对应要上传的Name，Value：本地文件名</param>
        /// <param name="timeOut">超时</param>
        /// <returns></returns>
        public static string HttpPost(string url, CookieContainer cookieContainer = null, Stream postStream = null, Dictionary<string, string> fileDictionary = null, string refererUrl = null, Encoding encoding = null, int timeOut = 1200000)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            request.Method = "POST";
            request.Timeout = timeOut;

            #region 处理Form表单文件上传
            var formUploadFile = fileDictionary != null && fileDictionary.Count > 0;//是否用Form上传文件
            if (formUploadFile)
            {
                //通过表单上传文件
                postStream = postStream ?? new MemoryStream();

                string boundary = "----" + DateTime.Now.Ticks.ToString("x");
                //byte[] boundarybytes = Encoding.ASCII.GetBytes("
--" + boundary + "
");
                string fileFormdataTemplate = "
--" + boundary + "
Content-Disposition: form-data; name="{0}"; filename="{1}"
Content-Type: application/octet-stream

";
                string dataFormdataTemplate = "
--" + boundary +
                                              "
Content-Disposition: form-data; name="{0}"

{1}";
                foreach (var file in fileDictionary)
                {
                    try
                    {
                        var fileName = file.Value;

                        //准备文件流
                        using (var fileStream = GetFileStream(fileName))
                        {
                            string formdata = null;
                            if (fileStream != null)
                            {
                                //存在文件
                                formdata = string.Format(fileFormdataTemplate, file.Key, /*fileName*/ Path.GetFileName(fileName));
                            }
                            else
                            {
                                //不存在文件或只是注释
                                formdata = string.Format(dataFormdataTemplate, file.Key, file.Value);
                            }

                            //统一处理
                            var formdataBytes = Encoding.UTF8.GetBytes(postStream.Length == 0 ? formdata.Substring(2, formdata.Length - 2) : formdata);//第一行不需要换行
                            postStream.Write(formdataBytes, 0, formdataBytes.Length);

                            //写入文件
                            if (fileStream != null)
                            {
                                byte[] buffer = new byte[1024];
                                int bytesRead = 0;
                                while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
                                {
                                    postStream.Write(buffer, 0, bytesRead);
                                }
                            }
                        }
                    }
                    catch (Exception ex)
                    {
                        throw ex;
                    }
                }
                //结尾
                var footer = Encoding.UTF8.GetBytes("
--" + boundary + "--
");
                postStream.Write(footer, 0, footer.Length);

                request.ContentType = string.Format("multipart/form-data; boundary={0}", boundary);
            }
            else
            {
                request.ContentType = "application/x-www-form-urlencoded";
            }
            #endregion

            request.ContentLength = postStream != null ? postStream.Length : 0;
            request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";
            request.KeepAlive = true;

            if (!string.IsNullOrEmpty(refererUrl))
            {
                request.Referer = refererUrl;
            }
            request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.57 Safari/537.36";

            if (cookieContainer != null)
            {
                request.CookieContainer = cookieContainer;
            }

            #region 输入二进制流
            if (postStream != null)
            {
                postStream.Position = 0;

                //直接写入流
                Stream requestStream = request.GetRequestStream();

                byte[] buffer = new byte[1024];
                int bytesRead = 0;
                while ((bytesRead = postStream.Read(buffer, 0, buffer.Length)) != 0)
                {
                    requestStream.Write(buffer, 0, bytesRead);
                }

                //debug
                postStream.Seek(0, SeekOrigin.Begin);
                StreamReader sr = new StreamReader(postStream);
                var postStr = sr.ReadToEnd();
                postStream.Close();//关闭文件访问
            }
            #endregion

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();

            if (cookieContainer != null)
            {
                response.Cookies = cookieContainer.GetCookies(response.ResponseUri);
            }

            using (Stream responseStream = response.GetResponseStream())
            {
                using (StreamReader myStreamReader = new StreamReader(responseStream, encoding ?? Encoding.GetEncoding("utf-8")))
                {
                    string retString = myStreamReader.ReadToEnd();
                    return retString;
                }
            }
        }

    }
}

 上传微信永久素材图片  //请求头部信息media 

using System;
using System.IO;
using System.Net;
using System.Text;
using System.Web;

namespace BoldSeas.WeChat.Common.Rest
{
    public static class HttpUploadFile
    {
        public static string HttpUploadImgFile(string url, HttpPostedFileBase upImg)
        {
            // 设置参数
            var request = WebRequest.Create(url) as HttpWebRequest;
            request.CookieContainer = new CookieContainer();
            request.AllowAutoRedirect = true;
            request.Method = "POST";
            string boundary = DateTime.Now.Ticks.ToString("X"); // 随机分隔线
            request.ContentType = "multipart/form-data;charset=utf-8;boundary=" + boundary;
            byte[] itemBoundaryBytes = Encoding.UTF8.GetBytes("
--" + boundary + "
");
            byte[] endBoundaryBytes = Encoding.UTF8.GetBytes("
--" + boundary + "--
");
            string fileName = upImg.FileName;

            //请求头部信息
            StringBuilder sbHeader =
                new StringBuilder(string.Format(
                        "Content-Disposition:form-data;name="media";filename="{0}"
Content-Type:application/octet-stream

",
                        fileName));
            byte[] postHeaderBytes = Encoding.UTF8.GetBytes(sbHeader.ToString());

            Stream fs = upImg.InputStream;
            byte[] bArr = new byte[fs.Length];
            fs.Read(bArr, 0, bArr.Length);
            fs.Close();

            Stream postStream = request.GetRequestStream();
            postStream.Write(itemBoundaryBytes, 0, itemBoundaryBytes.Length);
            postStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);
            postStream.Write(bArr, 0, bArr.Length);
            postStream.Write(endBoundaryBytes, 0, endBoundaryBytes.Length);
            postStream.Close();

            //发送请求并获取相应回应数据
            HttpWebResponse response = request.GetResponse() as HttpWebResponse;
            //直到request.GetResponse()程序才开始向目标网页发送Post请求
            Stream instream = response.GetResponseStream();
            using (StreamReader myStreamReader = new StreamReader(instream, Encoding.UTF8))
            {
                string retString = myStreamReader.ReadToEnd();
                return retString;
            }
        }
    }
}