C# 提交表单

public static class HttpRequestPost
{

    /// <summary>
    /// 向指定的URL地址发起一个POST请求，同时可以上传一些数据项。
    /// </summary>
    /// <param name="url">要请求的URL地址</param>
    /// <param name="keyvalues">要上传的数据项</param>
    /// <param name="encoding">发送，接收的字符编码方式</param>
    /// <returns>服务器的返回结果</returns>
   public static string SendHttpRequestPost(string url, Dictionary<string, string> keyvalues, Encoding encoding)
    {
        if (string.IsNullOrEmpty(url))
        {
            throw new ArgumentNullException("url");
        }
        //name1=value&name2=value
        if (encoding == null)
        {
            encoding = Encoding.UTF8;
        }
        var mm = string.Join("&", (from m in keyvalues let keys = m.Key + "=" + HttpUtility.UrlEncode(m.Value) select keys).ToArray());
        HttpWebRequest web = (HttpWebRequest)WebRequest.Create(url);
        web.Method = "POST";
        web.ContentType = "application/x-www-form-urlencoded";


        byte[] data = encoding.GetBytes(mm);
        StreamWriter writer = new StreamWriter(web.GetRequestStream(), encoding);
        writer.Write(data);

        using (WebResponse reon = web.GetResponse())
        {
            using (StreamReader read = new StreamReader(reon.GetResponseStream(), encoding))
            {
                return read.ReadToEnd();
            }
        }

    }

    /// <summary>
    /// 向指定的URL地址发起一个POST请求，同时可以上传一些数据项以及上传文件。
    /// </summary>
    /// <param name="url">要请求的URL地址</param>
    /// <param name="keyvalues">要上传的数据项</param>
    /// <param name="fileList">要上传的文件列表</param>
    /// <param name="encoding">发送数据项，接收的字符编码方式</param>
    /// <returns>服务器的返回结果</returns>
   public static string SendHttpRequestPost(string url, Dictionary<string, string> keyvalues, Dictionary<string, string> fileList, Encoding encoding)
    {
        if (string.IsNullOrEmpty(url))
        {
            throw new ArgumentNullException("URL");
        }
        if (encoding == null)
        {
            encoding = Encoding.UTF8;
        }
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
        request.Method = "POST";


        string boundary = "------------------" + Guid.NewGuid().ToString("N");
        byte[] boundaryBytes = Encoding.ASCII.GetBytes("\r\n" + boundary + "\n\r");
        request.ContentType = "multipart/form-data; boundary=" + boundary;

        Stream stream = request.GetRequestStream();
        foreach (var m in keyvalues)
        {
            // 写入数据块的分隔标记
            stream.Write(boundaryBytes, 0, boundaryBytes.Length);
            string str = string.Format("Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}", m.Key, m.Value);
            byte[] date = encoding.GetBytes(str);
            stream.Write(date, 0, date.Length);
        }

        foreach (var m in fileList)
        {
            // 写入数据块的分隔标记
            stream.Write(boundaryBytes, 0, boundaryBytes.Length);
            // 写入文件描述，这里设置一个通用的类型描述：application/octet-stream，具体的描述在注册表里有。
            string description = string.Format(
                    "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\n" +
                    "Content-Type: application/octet-stream\r\n\r\n",
                    m.Key, Path.GetFileName(m.Value));

            // 注意：这里如果不使用UTF-8，对于汉字会有乱码。
            byte[] header = Encoding.UTF8.GetBytes(description);
            stream.Write(header, 0, header.Length);

            // 写入文件内容
            byte[] body = File.ReadAllBytes(m.Value);
            stream.Write(body, 0, body.Length);

        }
        // 写入结束标记
        boundaryBytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
        stream.Write(boundaryBytes, 0, boundaryBytes.Length);
        stream.Close();

        using (WebResponse wr = request.GetResponse())
        {
            StreamReader read = new StreamReader(wr.GetResponseStream(), encoding);
            return read.ReadToEnd();
        }

    }

}