Basic data validation in Silverlight

Silverlight 2 supports basic data validation capabilities. In Silverlight 2, when we bind data to a UI control, the validation rules that the data has are automatically bound to the UI control.

For example, a data field is set to an integer type, and an error occurs when we update the field with a non-integer data. We can use this rule to validate input data in the UI. To do this, we simply set two XAML properties and implement the desired UI behavior in the defined event.

For example, the following XAML code defines a set of controls in which the user updates the data through a textbox:

﹤StackPanel　x:Name="dataForm"﹥
　﹤TextBlock　Text="FirstName"　Width="125"　 FontSize="12"　/﹥
　﹤TextBox　x:Name="FirstNameTextBox"　IsReadOnly="False"　 Width="150"　
Text="{Binding　FirstName,　Mode=TwoWay,　NotifyOnValidationError=true,　 ValidatesOnExceptions=true}"
BindingValidationError="FirstNameTextBox_BindingValidationEr ror"/﹥
　﹤/StackPanel﹥　

When both the NotifyOnValidationError and Validatesonexceptions properties are set to True, Silverlight The Bindingvalidationerror event is triggered when an error occurs on the rule that the input data validation is bound to, so that we are notified when an error occurs in the validation.

What we're going to do next is to implement the behavior of the event trigger, which is the UI behavior we expect. Such as:

private　void　FirstNameTextBox_BindingValidationError(object　sender,　 ValidationErrorEventArgs　e)
{
　　if　(e.Action　==　 ValidationErrorEventAction.Added)
　　{
　　　　((Control)e.OriginalSource).Background 　=　new　SolidColorBrush(Colors.Red);
　　　　this.Dispatcher.BeginInvoke(() =>HtmlPage.Window.Alert("The　input　format　is　invalid"));
　　}
　　if　 (e.Action　==　ValidationErrorEventAction.Removed)
　　{
　　　　((Control) e.OriginalSource).Background　=　new　SolidColorBrush(Colors.White);
　　}
}　

In the above code, when the error occurs, the background color of the control (this is the TextBox) turns red and the user is prompted with a warning window for the HTML page. When the error is corrected, the space is restored to the default white.