Why am I getting "The name Regex does not exist in the current context" from my C# code?

Question

Why am I getting this error:

The name Regex does not exist in the current context.

from my code?

if (Regex.IsMatch(string1, @"^[a-zA-Z]+$"))

Answer 1

Make sure you have the System.Text.RegularExpressions namespace referenced.

Answer 2

You need to include the right namespace to access the Regex class:

using System.Text.RegularExpressions;