Here’s a quick-and-dirty method to determine whether a string contains only uppercase characters

' the string to test is in the SOURCE variableIf System.Text.RegularExpressions.Regex.IsMatch(source, "^[A-Z]+$") Then    Console.WriteLine("Uppercase string")End If

If the source string can contain accented wovel, you should modify the regular expresson pattern to account for them as well

If System.Text.RegularExpressions.Regex.IsMatch(source, _    "^[A-ZÀÈÉÌÍÒÓÙÚ]+$") Then    Console.WriteLine("Uppercase string")End If

If you really want to test that the string doesn’t contain any uppercase character, that is, you want to check that you already have the lowercase version of the string, you can use another approach:

If String.Compare(source, source.ToUpper) = 0 Then    Console.WriteLine("Uppercase string")End If