使用WebClient发送POST请求

  /// <summary>
    /// 发送post请求
    /// </summary>
    /// <param name="url">请求的url</param>
    /// <param name="postString">发送到数据 例如:"name=xhan&password=1231"</param>
    /// <param name="encoding">发送和接受数据使用的编码</param>
    /// <returns>服务器响应字符串</returns>
    public static string SendPostRequest(string url, string postString,Encoding encoding)
    {
        byte[] postData = encoding.GetBytes(postString);

        WebClient client = new WebClient();
        client.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
        client.Headers.Add("ContentLength", postData.Length.ToString());

        byte[] responseData = client.UploadData(url, "POST", postData);
        return encoding.GetString(responseData);
    }