根据URL接口地址获取JSON数据

//根据URL回发地址获取用户json数据
        private string GetJsonByUrl(string url)
        {
            System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(url);
            System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)request.GetResponse();
            System.IO.Stream responseStream = response.GetResponseStream();
            System.IO.StreamReader sr = new System.IO.StreamReader(responseStream, System.Text.Encoding.GetEncoding("utf-8"));
            string responseText = sr.ReadToEnd();
            sr.Close();
            sr.Dispose();
            responseStream.Close();
            string jsonData = responseText;
            return jsonData;
        }