using System.Text.RegularExpressions; // to get Regex namespace Packt.Shared; public static class StringExtensions { public static bool IsValidEmail(this string input) { // use a simple regular expression to check // that the input string is a valid email return Regex.IsMatch(input, @"[a-zA-Z0-9\.-_]+@[a-zA-Z0-9\.-_]+"); } }