با سلام

از کد زیر برای کوتاه ککنده لینک استفاده میکنم اما با خطای زیر مواجه میشم

private const string key = "xxxxxx mykey xxxxxxx";
    protected void Button1_Click(object sender, EventArgs e)
    {
        string url = TextBox1.Text;
        string post = "{\"longUrl\": \"" + url + "\"}";
        string shortUrl = url;
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://www.googleapis.com/urlshortener/v1/url?key=" + key);
 
            request.ServicePoint.Expect100Continue = false;
            request.Method = "POST";
            request.ContentLength = post.Length;
            request.ContentType = "application/json";
            request.Headers.Add("Cache-Control", "no-cache");

            using (Stream requestStream = request.GetRequestStream())
            {
                byte[] postBuffer = Encoding.ASCII.GetBytes(post);
                requestStream.Write(postBuffer, 0, postBuffer.Length);
            }

            using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
            {
                using (Stream responseStream = response.GetResponseStream())
                {
                    using (StreamReader responseReader = new StreamReader(responseStream))
                    {
                        string json = responseReader.ReadToEnd();
                        shortUrl = Regex.Match(json, @"""id"": ?""(?<id>.+)""").Groups["id"].Value;
                    Response.Write(shortUrl);
                    }
                }
            }
            
         
        

    }