How to get a resource from a merged ResourceDictionary in a code-behind file?

Question

I have a custom look-less control derived from Control class. It's template is defined in Generic.xaml file. Now I want to add some UI stuff to it (mostly brushes) and want to do that in separate resource dictionary, and then access those stuff from the code-behind feil (*.xaml.cs). See bellow: Generic.xaml (fragment):

<ResourceDictionary
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:PTE.Controls" xmlns:sys="clr-namespace:System;assembly=mscorlib">
<ResourceDictionary.MergedDictionaries>
    <ResourceDictionary Source="PTE.Controls;component/Resources/CategoriesColors.xaml"/>
</ResourceDictionary.MergedDictionaries>
<CornerRadius x:Key="elementCornerBorder" BottomLeft="2" BottomRight="2" TopLeft="2" TopRight="2"/> 
<Style TargetType="{x:Type local:Element}">
    <Setter Property="Canvas.ZIndex" Value="50"/>
    <Setter Property="MinWidth" Value="60"/>
    <Setter Property="Template">...

CategoriesColors.xaml (fragment):

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;
<LinearGradientBrush StartPoint="0,1" EndPoint="1,0" x:Key="categoryNobleGas">
    <GradientStop Color="White" Offset="0"/>
    <GradientStop Color="RoyalBlue" Offset="0.5"/>
    <GradientStop Color="SteelBlue" Offset="1"/>
</LinearGradientBrush>...

Server side part (fragment):

        private static void OnCategoryNameChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var categoryName = (CategoryName)e.NewValue;
        var element = (Element) d;
        switch (categoryName)
        {
            case CategoryName.NobleGas:
                element.Background = (Brush)element.TryFindResource("categoryNobleGas");
                break;
            case CategoryName.Halogen:
                element.Background = (Brush)element.TryFindResource("categoryHalogen");
                break;
            case CategoryName.OtherNonmetal:
                element.Background = (Brush)element.TryFindResource("categoryOtherNonmetal");
                break;
            case CategoryName.Metalloid:

It doesn't work. Basically TryFindResource method always returns null. Any ideas how to make these stuff work together? Thank you!

UPD: If I add following line in the constructor of the control it works:

this.Resources = Application.LoadComponent(new Uri("PTE.Controls;Component/Resources/CategoriesColors.xaml", UriKind.Relative)) as ResourceDictionary;

But first, it will duplicate dictionary (load new one every time) and consume considerable more memory. Second, I really want to do it in XAML.

Answer 1

Try adding / in the ResourceDictionary inside the MergedDictionaries like below. Infront of PTE

<ResourceDictionary Source="/PTE.Controls;component/Resources/CategoriesColors.xaml"/>

HTH