Regex.IsMatch method

There is one method to call, Regex.IsMatch.

It is overloaded means that this function will accept different lists of arguments.  In this case there are two versions of Regex.IsMatch.  The first version accepts two arguments, the second overloaded version accepts three arguments.

So we can use it like this:

Version 1 (two args):  Regex.IsMatch(value, @"^[a-zA-Z0-9]*$");

Or like this:

Version 2 (three args):  Regex.IsMatch(value, @"^[a-zA-Z0-9]*$", RegexOptions.IgnoreCase)

The signatures of the two overloads are:

public static bool IsMatch(string input, string pattern)
public static bool IsMatch(string input, string pattern, RegexOptions options)

As you'll see the difference between the two is that the second one allows you to pass a RegexOptions value as a third parameter.

This allows you to do things such as ignoring case when matching strings and to use Multiline mode. The latter changes the meaning of ^ and $ so they match at the beginning and end, respectively, of any line, and not just the beginning and end of the entire string.

Check this MSDN link for the full list of RegexOptions values:

http://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regexoptions(v=vs.110).aspx