The invalid URI: URI string is too long about dotnetopenauth HOT 1 CLOSED

            var kv = request.Form.AsKeyValuePairs();
            try
            {
                httpRequest.Content = new FormUrlEncodedContent(kv);
            }
            catch (Exception ex)//The invalid URI: URI string is too long.
            {
               //Do it in this way
                if (kv != null && kv.Count() > 0)
                {
                    string str = string.Join("&",
                        kv.Select(i =>
                        string.Concat(HttpUtility.UrlEncode(i.Key), '=', HttpUtility.UrlEncode(i.Value))).ToArray());
                    httpRequest.Content = new StringContent(str);
                }
            }
        }
        else if (request.InputStream != null)
        {
            httpRequest.Content = new StreamContent(request.InputStream);
        }