WPF - Manipulating VisualState from UserControl

Question

I have two visual states defined in my MainWindow LayoutRoot grid, as shown below:

<Grid x:Name="LayoutRoot" Background="#FF434343" ShowGridLines="True">

<Grid.RowDefinitions>
    <RowDefinition Height="100"/>
    <RowDefinition Height="*"/>
</Grid.RowDefinitions>


    <VisualStateManager.CustomVisualStateManager>
        <ic:ExtendedVisualStateManager/>
    </VisualStateManager.CustomVisualStateManager>
    <VisualStateManager.VisualStateGroups>
        <VisualStateGroup x:Name="VisualStateLogin">
            <VisualStateGroup.Transitions>
                <VisualTransition GeneratedDuration="00:00:00.6000000"/>
            </VisualStateGroup.Transitions>
            <VisualState x:Name="LoggedOn">
                <Storyboard>
                    <ObjectAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.0010000" Storyboard.TargetName="{x:Null}" Storyboard.TargetProperty="(Window.WindowStyle)">
                        <DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{x:Static WindowStyle.None}"/>
                    </ObjectAnimationUsingKeyFrames>
                    <BooleanAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.0010000" Storyboard.TargetName="{x:Null}" Storyboard.TargetProperty="(Window.AllowsTransparency)">
                        <DiscreteBooleanKeyFrame KeyTime="00:00:00" Value="True"/>
                    </BooleanAnimationUsingKeyFrames>
                </Storyboard>
            </VisualState>
            <VisualState x:Name="LoggedOff">
                <Storyboard>
                    <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.0010000" Storyboard.TargetName="brdContent" Storyboard.TargetProperty="(UIElement.Opacity)">
                        <SplineDoubleKeyFrame KeyTime="00:00:00" Value="0.1"/>
                    </DoubleAnimationUsingKeyFrames>
                    <BooleanAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.0010000" Storyboard.TargetName="brdContent" Storyboard.TargetProperty="(UIElement.IsEnabled)">
                        <DiscreteBooleanKeyFrame KeyTime="00:00:00" Value="False"/>
                    </BooleanAnimationUsingKeyFrames>
                    <BooleanAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.0010000" Storyboard.TargetName="ucTabButtons" Storyboard.TargetProperty="(UIElement.IsEnabled)">
                        <DiscreteBooleanKeyFrame KeyTime="00:00:00" Value="False"/>
                    </BooleanAnimationUsingKeyFrames>
                    <DoubleAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.0010000" Storyboard.TargetName="ucTabButtons" Storyboard.TargetProperty="(UIElement.Opacity)">
                        <SplineDoubleKeyFrame KeyTime="00:00:00" Value="0.4"/>
                    </DoubleAnimationUsingKeyFrames>
                </Storyboard>
            </VisualState>
        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>

It works great, switching from one state to another based on the MainWindow code, for example:

    void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        //ExtendedVisualStateManager.GoToElementState(this.LayoutRoot as FrameworkElement, "LoggedOff", false);        
    }

But now I need to be able to switch states from usercontrol inside MainWindow ...

I tried that:

    private void btnOk_Click(object sender, System.Windows.RoutedEventArgs e)
    {
        MainWindow parent = new MainWindow();
        Grid root = new Grid();
        root = (Grid)parent.FindName("LayoutRoot");
        ExtendedVisualStateManager.GoToElementState(root as FrameworkElement, "LoggedOn", true);
    }

And this gives me the following exception:

System.NullReferenceException was unhandled Message = "Object reference not set to object instance." Source = "WPFToolkit"

Does anyone know how to switch states from usercontrol?

ThankYou,

Josi

Answer 1

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:

public interface IStateChanger
{
    void GoToElementState(string state);    
}

MainWindow :

    void IStateChanger.GoToElementState(string state)
    {
        ExtendedVisualStateManager.GoToElementState(this.LayoutRoot as FrameworkElement, state, false);        
    }

, , :

    private void btnOk_Click(object sender, System.Windows.RoutedEventArgs e)
    {
        MainWindow parent = new MainWindow();
        if (parent is IStateChanger)
            ((IStateChanger)parent).GoToElementState("LoggedOn");
    }

Answer 2

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