利用BasicAuthorization方式直接调用接口发送微博，无需采用oauth方式需要不停的授权活动用access_token来做。

gistfile1.cs

namespace Utils
{
/*
Dictionary<string, string> texts = new Dictionary<string, string>();
texts.Add("source", "app key");
texts.Add("status", "post weibo test " + DateTime.Now.ToString());
texts.Add("visible", "2");

Dictionary<string, string> files = new Dictionary<string, string>();
files.Add("G:\\Desktop\\wiki_logo.png", "image/png");

string json_result = Utils.PostUtils.Post2Weibo(texts, files);
*/
    using System;
    using System.IO;
    using System.Text;
    using System.Net;
    public class PostUtils
    {
        public static string Post2Weibo(Dictionary<string, string> texts, Dictionary<string, string> files)
        {
            string username = "weibo_username";
            string password = "weibo_password";
            string url = "https://upload.api.weibo.com/2/statuses/upload.json";
            string boundary = "--------------------------------YokerWu";
            byte[] boundarybytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "\r\n");

            Uri myUri = new Uri(url);

            WebRequest myWebRequest = HttpWebRequest.Create(myUri);
            NetworkCredential myNetworkCredential = new NetworkCredential(username, password);
            CredentialCache myCredentialCache = new CredentialCache();
            myCredentialCache.Add(myUri, "Basic", myNetworkCredential);

            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(myUri);
            request.Method = "POST";
            request.ContentType = "multipart/form-data; boundary=" + boundary;
            request.Accept = "*/*";
            request.Timeout = 15000;
            request.PreAuthenticate = true;
            request.Credentials = myCredentialCache;
            request.Headers.Add("Authorization", "Basic " + Convert.ToBase64String(Encoding.ASCII.GetBytes(username + ":" + password)));


            Stream requestStream = null;
            WebResponse response = null;
            string responseStr = null;

            try
            {
                requestStream = request.GetRequestStream();

                #region 提交文本字段数据
                string tpl_text = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
                foreach (string key in texts.Keys)
                {
                    string value = texts[key];
                    if (value == null) { continue; }
                    byte[] textbytes = Encoding.UTF8.GetBytes(string.Format(tpl_text, key, value));
                    requestStream.Write(boundarybytes, 0, boundarybytes.Length);
                    requestStream.Write(textbytes, 0, textbytes.Length);
                }
                #endregion

                #region 提交文件数据流
                string tpl_file = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n";
                foreach (string filename in files.Keys)
                {
                    string content_type = files[filename];
                    byte[] filebytes = Encoding.UTF8.GetBytes(string.Format(tpl_file, "pic", filename, content_type));
                    requestStream.Write(boundarybytes, 0, boundarybytes.Length);
                    requestStream.Write(filebytes, 0, filebytes.Length);
                    FileStream fileStream = new FileStream(filename, FileMode.Open, FileAccess.Read);
                    byte[] buffer = new byte[4096];
                    int bytesRead = 0;
                    while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
                    {
                        requestStream.Write(buffer, 0, bytesRead);
                    }
                    fileStream.Close();
                }
                #endregion

                #region 提交结尾数据包
                byte[] footerbytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");
                requestStream.Write(footerbytes, 0, footerbytes.Length);
                #endregion

                requestStream.Close();

                response = request.GetResponse();
                if (response != null)
                {
                    StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
                    responseStr = reader.ReadToEnd();
                    reader.Close();
                }
            }
            catch (Exception)
            {
                throw;
            }
            finally
            {
                request = null;
                requestStream = null;
                response = null;
            }

            return responseStr;
        }
    }
}