How to assign WPF resources to other resource tags

Question

This is quite obscure, I may just be missing something extremely simple.

Scenario 1

Lets say I create a gradient brush, like this in my

Answer 1

I was wondering when someone was going to ask about this.

What you want to do in Scenario 1 is to effectively give a single resource an "alias." This is easily done by markup that seems obvious only after you see it. Suppose we have this in our App.xaml or somewhere:

<ResourceDictionary>
  <LinearGradientBrush x:Key="GridRowSelectedBackBrushGradient" ... />
</ResourceDictionary>

To include an alias in another ResourceDictionary, just:

<ResourceDictionary>
  <StaticResourceExtension x:Key="{x:Static SystemColors.HighlightBrushKey}"
                           ResourceKey="GridRowSelectedBackBrushGradient" />
</ResourceDictionary>

This looks up the brush object in the first ResourceDictionary and adds the same object to the second ResourceDictionary under a new key. This also works within a single ResourceDictionary.

For your Scenario 2 the solution is just as simple:

<Binding.ConverterParameter>
  <x:Array Type="{x:Type Brush}">
    <StaticResourceExtension ResourceKey="DataGridRowBackgroundBrush" />
    <StaticResourceExtension ResourceKey="DataGridRowBackgroundAltBrush" />
  </x:Array>
</Binding.ConverterParameter>

Again, the actual Brush objects found via the ResourceKey are added directly to the Brush[] array. No new Brush is created.

I think we're all so used to using StaticResourceExtension with markup extension syntax (eg {StaticResource Xyz}) that it's easy to forget that it can also be used with regular element syntax as well.

Answer 2

The markup you're working with doesn't go up far enough. You don't create a LinearGradientBrush, your first example: you just reference the resource. For example:

<DataGrid HighlightBrushKey="{StaticResource GridRowSelectedBackBrushGradient}"  ....

In your second example, I'd say that you want to declare the array as a resource:

<x:Array Type="{x:Type Brush}" x:Key="MyArray">
  <SolidColorBrush Color="#EAF2FB" />
  <SolidColorBrush Color="#FFFFFF" />
</x:Array>

And then you can use

<Binding RelativeSource="{RelativeSource Mode=Self}" 
         Converter="{StaticResource BackgroundBrushConverter}"
         ConverterParameter="{Staticresource MyArray}" />