A regular expression that allows only certain characters in .net

Question

I just worked on some validation and was fixated on that, though :( I want a text containing only [az] [AZ] [0-9] [_].

It must accept any of these characters any number of times in any order. All other characters are marked as invalid.
I tried this, but it does not work!

  {
        ......

        Regex strPattern = new Regex("[0-9]*[A-Z]*[a-z]*[_]*");

        if (!strPattern.IsMatch(val))
        {
            return false;
        }

        return true
  }

Answer 1

Do you want to:

Regex strPattern = new Regex("^[0-9A-Za-z_]*$");

Your expression does not work because:

• , , , . , , , .
• ^ $. , , . (, "! @# $" ..!). , , , .
• - . , , * +. (* "0 ", + "1 ".)

Answer 2

:

new Regex("[0-9A-Za-z_]*");