Using RegEx this VB.NET code validates an email address. It's checking for a string separated by the at (@) character, and again separated by a dot.

1. Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
2.  ‘ The regular expression rule
3.  Dim Expression As New 
System.Text.RegularExpressions.Regex("\S+@\S+\.\S+")
4.  ' If the email matches the regular expression
5.  If Expression.IsMatch("[email protected]") Then
6.         MessageBox.Show("The email address is valid.")
7.  Else
8.         MessageBox.Show("The email address is NOT valid.")
9.  End If
10. End Sub