Validate email address from GUI

How do I check if the user enters the correct format of the email address in the GUI they typed in?

 

Usually this is done with regular expressions: http://regexlib.com/Search.aspx?k=email&AspxAutoDetectCookieSupport=1

 

Here is a class that I grabbed from somewhere:

Code (CSharp):

1. /*
2. * File: TestEmail.cs
3. * Author: Mykola Dobrochynskyy
4. * Version 1.0
5. * Created date:  07.01.2008
6. * Last upadte date:
7. * Project: Common Utils
8. * Description: Implements the static class, that could be used to check an E-Mail address.
9. * -----------------------------------------------------------------------------
10. * You are eligible to use this code for you own purpouse assuming that this
11. * code and information in it is provided "AS IS" without warranty of any kind
12. * expressed or implied.
13. * ------------------------------------------------------------------------------
14. */
15. using System;
16. using System.Collections.Generic;
17. using System.Text;
18. using System.Text.RegularExpressions;
19.  
20. //namespace Dobro.Text.RegularExpressions
21. //{
22.     /// <summary>
23.     /// Tests an E-Mail address.
24.     /// </summary>
25.     public static class TestEmail
26.     {
27.         /// <summary>
28.         /// Regular expression, which is used to validate an E-Mail address.
29.         /// </summary>
30.         public const string MatchEmailPattern =
31.             @"^(([\w-]+\.)+[\w-]+|([a-zA-Z]{1}|[\w-]{2,}))@"
32.                 + @"((([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\."
33.                 + @"([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])){1}|"
34.                 + @"([a-zA-Z]+[\w-]+\.)+[a-zA-Z]{2,4})$";
35.        
36.        
37.         /// <summary>
38.         /// Checks whether the given Email-Parameter is a valid E-Mail address.
39.         /// </summary>
40.         /// <param name="email">Parameter-string that contains an E-Mail address.</param>
41.         /// <returns>True, wenn Parameter-string is not null and contains a valid E-Mail address;
42.         /// otherwise false.</returns>
43.         public static bool IsEmail(string email)
44.         {
45.             if (email != null) return Regex.IsMatch(email, MatchEmailPattern);
46.             else return false;
47.         }
48.     }
49. //}

 

Thanks, but how do I grab the text from GUI text box and compare with the regular expression?