只可輸入英文和數字

//Convert text to uppercase
            this.DeliveryTermCodeTextBox.Text = this.DeliveryTermCodeTextBox.Text.ToUpper();
            //Put the cursor on the last
            this.DeliveryTermCodeTextBox.SelectionStart = this.DeliveryTermCodeTextBox.Text.Length;
            //Restrict the user to input Chinese
            Regex r = new Regex(@"^[A-Za-z0-9]+$");
            Match mh = r.Match(this.DeliveryTermCodeTextBox.Text.Trim());
            if (!mh.Success && this.DeliveryTermCodeTextBox.Text.Length > 0)
            {
                //If the user enters the Chinese replaced with empty
                this.DeliveryTermCodeTextBox.Text = this.DeliveryTermCodeTextBox.Text.Replace(
                    this.DeliveryTermCodeTextBox.Text.Substring(this.DeliveryTermCodeTextBox.Text.Length - 1, 1), "");
                MessageBox.Show("只可輸入英文和數字");
                this.DeliveryTermCodeTextBox.Focus();
            }