Still not sure about what you are asking, so I'll try to answer both.
If the "url" field is the string "http:\website.us?DKT_ID=param", you can get the string "DKT_ID=param" by using
url.Split('?')[1]
Creating a Uri object does not do anything other than parse your string into a special object, if you want to peform an HTTP Get and use data from that URL, use something like the example from MSDN:
WebRequest request = WebRequest.Create (
"http:\\website.us?DKT_ID=param");
// If required by the server, set the credentials.
request.Credentials = CredentialCache.DefaultCredentials;
// Get the response.
WebResponse response = request.GetResponse ();
// Get the stream containing content returned by the server.
Stream dataStream = response.GetResponseStream ();
// Open the stream using a StreamReader for easy access.
StreamReader reader = new StreamReader (dataStream);
// Read the content.
string responseFromServer = reader.ReadToEnd ();
// Display the content.
textBox1.Text = responseFromServer;
// Clean up the streams and the response.
reader.Close ();
response.Close ();
Update If you want just the "param" string, and there won't be ANY other parameters in the query string, just use
url.Split('=')[1]
If there are multiple parameters, then you need to do something like
Dictionary<String,String> params;
string[] queryParams = url.Split('?')[1].Split('&');
foreach (string s in queryParams)
{
string[] queryParameter = s.Split('=');
params.Add(queryParameter[0], queryParameter[1]);
}
textBox1.Text = queryParams["DKT_ID"];