private void Button_Click(object sender, RoutedEventArgs e)
        {
            WindowUtilities.FixFocus(this, CheckPasteAsBase64Content);
            if (sender == ButtonCancel)
            {
                DialogResult = false;
            }
            else
            {
                DialogResult = true;
            }

            Close();
        }
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            WindowUtilities.FixFocus(this, CheckExternalLink);

            if (DialogResult == null)
            {
                if (sender == ButtonCancel)
                {
                    DialogResult = false;
                }
                else
                {
                    mmApp.Configuration.LastLinkExternal = IsExternal;
                    DialogResult = true;
                }
            }

            Close();
        }