Win8 在TextBox中设置提示信息，当TextBox获得焦点时消失，失去时验证

// 在获得焦点时，验证文本内容是否与提示信息相同，相同则清除，并改变文本颜色

private void email_GotFocus(object sender, RoutedEventArgs e)
        {
            if (this.email.Text.Equals("[email protected]"))
            {
                this.email.Text = "";
            }
            this.email.Foreground = new SolidColorBrush(Colors.Black);
        }

// 在失去焦点时，验证文本内容是否为空（清除空格）,为空则重新设置提示信息，并改变颜色

private void email_LostFocus(object sender, RoutedEventArgs e)
        {
            if (0 == this.email.Text.Trim().Length)
            {
                this.email.Text = "[email protected]";
                this.email.Foreground = new SolidColorBrush(Colors.Gray);
            }
        }

//  效果图