C# Post 模拟表单提交

/// <summary>
/// 向指定的URL地址发起一个POST请求。
/// </summary>
/// <param name="url">要请求的URL地址</param>
/// <param name="keyvalues">要上传的数据项</param>
/// <returns>服务器的返回结果</returns>
public static string FormdataPost(string url, Dictionary<string, string> keyvalues, string Authorization)
{
    System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls12;
 
    if (string.IsNullOrEmpty(url))
        throw new ArgumentNullException("url");
 
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
    request.Method = "POST";
    request.KeepAlive = true;
    request.Headers.Add("Authorization", Authorization);//token
 
    string boundary = "---------------------------" + Guid.NewGuid().ToString("N");
 
    byte[] boundaryBytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");
 
 
    request.ContentType = "multipart/form-data; boundary=" + boundary;
 
 
    Stream stream = request.GetRequestStream();
 
    byte[] beginBoundaryBytes = Encoding.UTF8.GetBytes("--" + boundary + "\r\n");
    byte[] endBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");
 
    //写入参数
    if (keyvalues != null)
    {
        string formDataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n" +
               "{1}\r\n";
 
        foreach (string key in keyvalues.Keys)
        {
            string formItem = string.Format(formDataTemplate, key, keyvalues[key]);
            byte[] formItemBytes = Encoding.UTF8.GetBytes(formItem);
 
            stream.Write(beginBoundaryBytes, 0, beginBoundaryBytes.Length); // 1.1 写入FormData项的开始边界符
            stream.Write(formItemBytes, 0, formItemBytes.Length);   // 1.2 将键值对写入FormData项中
        }
    }
 
    boundaryBytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
    stream.Write(boundaryBytes, 0, boundaryBytes.Length);
 
    stream.Close();
 
    using (WebResponse response = request.GetResponse())
    {
        using (StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
        {
            return reader.ReadToEnd();
        }
    }
}