private void PhonetextBox_KeyDown(object sender, KeyEventArgs e)
 {
     if (e.KeyCode == Keys.Enter)
     {
         EmailAddresstextBox.Focus();
         e.Handled = true;
     }
 }
        private void EmailAddresstextBox_Validating(object sender, CancelEventArgs e)
        {
            if (!string.IsNullOrEmpty(EmailAddresstextBox.Text))
            {
                string emailId = EmailAddresstextBox.Text.Trim();
                Regex  mRegxExpression;

                mRegxExpression = new Regex(@"^([a-zA-Z0-9_\-])([a-zA-Z0-9_\-\.]*)@(\[((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}|((([a-zA-Z0-9\-]+)\.)+))([a-zA-Z]{2,}|(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\])$");

                if (!mRegxExpression.IsMatch(emailId))
                {
                    MessageBox.Show("Please type your  valid email Address.", "MojoCRM", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    EmailAddresstextBox.Clear();
                    EmailAddresstextBox.Focus();
                }
            }
        }