How to do If Statement to detect multiple words in a string?

Question

private void ButtonCheck_Click(object sender, EventArgs e)

{

   string s = textBoxMessage.Text;

   if (s.Contains("FREE") == true)

   {

         MessageBox.Show("Its not a SPAM", "SMS SPAM DETECTION TOOL | KEYWORD",          MessageBoxButtons.OK, MessageBoxIcon.Information);

   }

   else if (s.Contains("GET") == true)

   {

         MessageBox.Show("Its a SPAM", "SMS SPAM DETECTION TOOL | KEYWORD",          MessageBoxButtons.OK, MessageBoxIcon.Information);

   }

   else

  {

         MessageBox.Show("Its not a SPAM", "SMS SPAM DETECTION TOOL", MessageBoxButtons.OK,          MessageBoxIcon.Information);

   }

}





I dont know how to detect multiple words in a sentence.