Vfrdtyky

I'm inheriting DatePicker in order to add IsReadOnly and InputRequired behaviour. have made corresponding visual states for both in CommonStates. The reason I have put it in CommonStates, is that they are both mutually exclusive with the Normal state (I checked TextBox and it the same implementation for IsReadOnly).

The problem I encounter is that even if I apply the InputRequired state in OnApplyTemplate, it does not actually update the appearance. It does however after a MouseEnter event, leading my to conclude that it is only on the initial construction/rendering.

From looking into the source code of Control I can see that in OnPostApplyTemplate, it calls an internal virtual UpdateVisualState method, which is overridden in DatePicker, and which applies the "Normal" state, meaning that my visual state update in OnApplyTemplate is overwritten by Control.

As a workaround I can update the visual state in the Loaded event, and I can also make it a separate VisualStateGroup, and have some more complex logic in the code to determine wether the apply the visual state (e.g. inputrequired should not be applied with disabled/readonly), but both of these feel a little bit hacked.

So my questions is: is there a correct way to inject new visual states in the CommonStates of a control in this way? Or is the best way to listen for the Loaded event and update visual state here (and are there any gotchas in this case)?

Visual states:

    <VisualStateGroup x:Name="CommonStates">

    <VisualState x:Name="Normal"/>

    <VisualState x:Name="MouseOver">

        <Storyboard>

            <ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetName="Background" Storyboard.TargetProperty="Fill">

                <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource CommonHoverBackgroundColor}"/>

            </ObjectAnimationUsingKeyFrames>

            <ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetName="Background" Storyboard.TargetProperty="Stroke">

                <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource CommonHoverBorderColor}"/>

            </ObjectAnimationUsingKeyFrames>

        </Storyboard>

    </VisualState>

    <VisualState x:Name="ReadOnly">

        <Storyboard>

            <DoubleAnimation To="1" Duration="0" Storyboard.TargetName="ReadOnlyVisual" Storyboard.TargetProperty="Opacity"/>

        </Storyboard>

    </VisualState>

    <VisualState x:Name="InputRequired">

        <Storyboard>

            <ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetName="Background" Storyboard.TargetProperty="Fill">

                <DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource CommonRequiredBackgroundColor}"/>

            </ObjectAnimationUsingKeyFrames>

        </Storyboard>

    </VisualState>

    <VisualState x:Name="Disabled">

        <Storyboard>

            <DoubleAnimation To="1" Duration="0" Storyboard.TargetName="PART_DisabledVisual" Storyboard.TargetProperty="Opacity"/>

        </Storyboard>

    </VisualState>

</VisualStateGroup>

UpdateVisualState in codebehind

private void UpdateVisualState(bool useTransitions = true)

    {

        // Common states

        if (IsEnabled == false)

        {

            VisualStateManager.GoToState(this, "Disabled", useTransitions);

        }

        else if (IsMouseOver)

        {

            VisualStateManager.GoToState(this, "MouseOver", useTransitions);

        }

        else if (IsReadOnly)

        {

            VisualStateManager.GoToState(this, "ReadOnly", useTransitions);

        }

        if (CheckInputRequired())

        {

            VisualStateManager.GoToState(this, "Required", useTransitions);

        }

        else

        {

            VisualStateManager.GoToState(this, "Normal", useTransitions);

        }



        if (IsKeyboardFocusWithin)

        {

            VisualStateManager.GoToState(this, "Focused", useTransitions);

        }

        else

        {

            VisualStateManager.GoToState(this, "Unfocused", useTransitions);

        }



        // Clearable states

        if (IsReadOnly == false && AllowNull && SelectedDate != null)

        {

            VisualStateManager.GoToState(this, "Clearable", useTransitions);

        }

        else

        {

            VisualStateManager.GoToState(this, "Unclearable", useTransitions);

        }



        // Watermark states

        if (IsKeyboardFocusWithin)

        {

            // When control has keyboard focus, always hide watermark.

            VisualStateManager.GoToState(this, "Unwatermarked", useTransitions);

        }

        else if (string.IsNullOrWhiteSpace(_datePickerTextBox?.Text) == false)

        {

            // If datepicker has any text, hide watermark.

            VisualStateManager.GoToState(this, "Unwatermarked", useTransitions);

        }

        else

        {

            VisualStateManager.GoToState(this, "Watermarked", useTransitions);

        }

    }