C# Regex for invalid characters

Question

Hi I have a requirement to validate an input that should accept only alphanumeric, -, _ To test this i am using the following code

 string pattern = @"[^a-z A-Z 0-9._-]$";
        var matches = Regex.Matches(m_ModelName.Value, pattern, RegexOptions.IgnoreCase);
        return (matches.Count > 0);

if the count is >0 it means there are invalid characters. But it never returns according to my expectations. Please tell me what I am doing wrong. This is strictly c#

Answer 1

string pattern = @"[^a-z A-Z 0-9._-]$";

This regex just matches the last character in the string (because of the $ anchor).

You probably want something like:

 string pattern = @"^[a-zA-Z0-9._-]+$";
 return Regex.IsMatch(m_ModelName.Value, pattern, RegexOptions.IgnoreCase);

Also you may look at the \\w character class.