title: Allow special characters before '@' while validating email address with regex
body: <p>Allow special characters before @ (i.e abc_@example.com).We are using the following regex:</p>
  
  <pre><code>class Program
  {
      static bool IsValid(string value)
      {
          return Regex.IsMatch(value, "^(?(\")(\".+?\"@)|(([0-9a-zA-Z]((\\.(?!\\.))|[-!#\\$%&amp;'\\*\\+/=\\?\\^`\\{\\}\\|~\\w])*)(?&lt;=[0-9a-zA-Z])@))(?(\\[)(\\[(\\d{1,3}\\.){3}\\d{1,3}\\])|(([0-9a-zA-Z][-\\w]*[0-9a-zA-Z]\\.)+[a-zA-Z]{2,6}))$");
      }
  
      static void Main(string[] args)
      {
          Console.WriteLine(IsValid("example211_@hotmail.com"));
          Console.ReadLine();
      }
  }
  </code></pre>