How to validate Email Address in Web Form in C#.NET

void EmailValidation(object sender, CancelEventArgs e)
       {
           System.Text.RegularExpressions.Regex rEMail = new System.Text.RegularExpressions.Regex(@"^[a-zA-Z][\w\.-]{0,68}[a-zA-Z0-9]@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z]$");
           if (txtEmail.Text.Length > 0)
           {
               if (!rEMail.IsMatch(txtEmail.Text))
               {
                   MessageBox.Show("Invalid e-mail id.", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                   txtEmail.SelectAll();
                   e.Cancel = true;
               }
           }
       }