C# Regular Expression to match letters, numbers and underscore

Question

I am trying to create a regular expression pattern in C#. The pattern can only allow for:

• letters
• numbers
• underscores

So far I am having little luck (i'm not good at RegEx). Here is what I have tried thus far:

// Create the regular expression string pattern = @"\w+_"; Regex regex = new Regex(pattern);  // Compare a string against the regular expression return regex.IsMatch(stringToTest); 

Answer 1

EDIT :

@"^[a-zA-Z0-9\_]+$" 

or

@"^\w+$"