web service using web url need help

Question

I am consuming a web serivce for sending sms below is my code 

private void button1_Click(object sender, RoutedEventArgs e)

{

string key = txtKey.Text;

string secret = txtSecret.Text;

string to = txtTo.Text;

string messages = txtMessage.Text;

string sURL;

StreamReader objReader;

sURL = "https://www.thetexting.com/rest/sms/json/message/send?api_key=" + key + "&api_secret=" + secret + "&to=" + to + "&text=" + messages;

WebRequest wrGETURL;

wrGETURL = WebRequest.Create(sURL);

try

{

Stream objStream;

objStream = wrGETURL.GetResponse().GetResponseStream();

MessageBox.Show("Message Send Successfully", "My Demo App");

objReader = new StreamReader(objStream);

objReader.Close();

}

catch (Exception ex)

{

MessageBox.Show("Something went wrong with your information", "My Demo App");

ex.ToString();

}

}

basically i am creating a url and when this below line executes my message send to the recepient

objStream = wrGETURL.GetResponse().GetResponseStream(); 

 

if i place the wrong credentials and after the execuation of the above line still it saying success message wether it is not sending message , how to check that objStream is successful or not ? i cannot verify the credentails from here , and the web service is just a url to if using input wrong credentials and sms not send how to show message of sms not send .