Silverlight: How do you perform validation on user controls?

Question

How to implement validation in user controls? I want to replicate the standard validation logic that you will see when binding TextBox data to a model or view model that provides IDataErrorInfo or INotifyDataErrorInfo.

Answer 1

To implement validation, you must add the ValidationStates group in the VisualStateManager of the control.

I will illustrate a simple user control TestControlwith a property TestProperty.

The style in Generic.xaml, depending on the state, displays blue text or a red frame with the first error message:

<Style TargetType="local:TestControl">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="local:TestControl">
                <Grid>
                    <VisualStateManager.VisualStateGroups>
                        <VisualStateGroup x:Name="ValidationStates">
                            <VisualState x:Name="Valid" />
                            <VisualState x:Name="InvalidFocused">
                                <Storyboard>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="InvalidBorder" Storyboard.TargetProperty="Visibility" Duration="0">
                                        <DiscreteObjectKeyFrame KeyTime="0" Value="Visible"/>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="InvalidUnfocused">
                                <Storyboard>
                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="InvalidBorder" Storyboard.TargetProperty="Visibility" Duration="0">
                                        <DiscreteObjectKeyFrame KeyTime="0" Value="Visible"/>
                                    </ObjectAnimationUsingKeyFrames>
                                </Storyboard>    
                            </VisualState>
                        </VisualStateGroup>
                    </VisualStateManager.VisualStateGroups>
                    <TextBlock Text="{TemplateBinding TestProperty}" Foreground="Blue" />
                    <Border x:Name="InvalidBorder"  BorderBrush="Red" BorderThickness="2" Visibility="Collapsed">
                        <TextBlock Text="{Binding (Validation.Errors)[0].ErrorContent, RelativeSource={RelativeSource TemplatedParent}}" Foreground="Red" FontWeight="Bold" />
                    </Border>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

3 :

• . .
• InvalidFocused - . , , . , Tab Tab , TextBox.
• InvalidUnfocused - , .

, :

public class TestControl : Control
{
    public TestControl()
    {
        this.DefaultStyleKey = typeof(TestControl);
    }

    public string TestProperty
    {
        get { return (string)GetValue(TestPropertyProperty); }
        set { SetValue(TestPropertyProperty, value); }
    }

    public static readonly DependencyProperty TestPropertyProperty =
        DependencyProperty.Register("TestProperty", typeof(string), typeof(TestControl), new PropertyMetadata(null));
}

, IDataErrorInfo, xaml:

<local:TestControl TestProperty="{Binding SomeModelProperty, ValidatesOnDataErrors=True}" />

INotifyDataErrorInfo xaml :

<local:TestControl TestProperty="{Binding SomeModelProperty}" />