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Asked: 2026-05-27T00:52:52+00:00

I have a customized WPF control that is derived from UserControl. In the Resources

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I have a customized WPF control that is derived from UserControl. In the Resources section in my XAML file I have several templates and styles defined for the items that will be displayed on my custom control.

Here is a definition for one of my styles to draw an downward pointing arrow.

    <Style x:Key="ArrowStyle" TargetType="Path">
        <Setter Property="Margin" Value="4"/>
        <Setter Property="Stretch" Value="Uniform"/>
        <Setter Property="HorizontalAlignment" Value="Center"/>
        <Setter Property="VerticalAlignment" Value="Center"/>
        <Setter Property="Data" Value="M 0 0 L 5 5 L 10 0 Z"/>
        <Setter Property="Fill" Value="{DynamicResource FormText}"/>
    </Style>

So, I have a custom buttom object that is derived from button. Basically it is a small square button that displays the arrow. In my constructor for my custom button I have the following code.

        Path Arrow = new Path();
        Arrow.Style = TryFindResource("ArrowStyle") as Style;

However, the call to TryFindResource fails indicated that it cannot location the resource. If I move the defined style into App.xaml it find it, but not when it is a custom control resource.

What am I doing wrong or missing?

Update

The custom button that I am calling TryFindResource for does reside on the custom user control. However, since I am calling TryFindResource in the constructor of the custom button it will not actually reside on the custom user control at the time TryFindResource is called. After the custom button is created it will be added to the custom user control. Perhaps there is a different way or place to put the TryFindResource so that it is called after the button belongs to the control.

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1 Answer

  1. Editorial Team

    TryFindResource traverses the logical tree upward, to the parent element until the root element is reached.

    Then application resources are checked. That is the one you put in the second try, and worked because it was found there.

    So when you say “TryFindResource(“ArrowStyle”), it searches the arrow style on its parent elements up to its window resources and then application resources (global resources). When you call it from your custom button object, it can’t find it because your ArrowStyle resource do not satisfy the conditions above.

    You need to call it on your “customized WPF control that is derived from UserControl” or descendants of it.

    I think if you can’t make it work just move it to application resources or add a resource dictionary to your application resources with all global resources (styles):

    <Application.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="....Your resources.xaml"/>
            <ResourceDictionary Source="....Your resources.xaml"/>
            <!-- Place further resources here -->
        </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
</Application.Resources>
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