Can I use a resource declared in its own XXX.Resources? - wpf

Question

I've a Window, in which I declare one Resource, I was hopping to be able to use it in the window itself, but I'm not sure this is possible?
<dx:ThemedWindow x:Class="SomeWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:dxco="http://schemas.devexpress.com/winfx/2008/xaml/controls"
xmlns:dxmvvm="http://schemas.devexpress.com/winfx/2008/xaml/mvvm"
xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
xmlns:frameworkExtensions="clr-namespace:SomeNamespace.FrameworkExtensions"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800" ContentTemplate="{StaticResource dataTemplate}" >
<dx:ThemedWindow.Resources>
<frameworkExtensions:ConventionBasedDataTemplateSelector x:Key="dataTemplate"/>
</dx:ThemedWindow.Resources>
[...]
</dx:ThemedWindow>
Here by example it's for a custom DataTemplate.
How should I do this? Because currently Visual Studio is warning me that it can't find "dataTemplate"

Answer 1

Your problem is because you're trying to use a resource before it's there.
Let's consider a simple example.
If you did:
<Window x:Class="WpfApp1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApp1"
mc:Ignorable="d"
Title="MainWindow" Height="200" Width="400"
>
<Window.Resources>
<SolidColorBrush x:Key="TestResourceBrush" Color="Blue"/>
</Window.Resources>
<Window.Background>
<StaticResource ResourceKey="TestResourceBrush"/>
</Window.Background>
<Grid>
</Grid>
</Window>
Then you see no error and the background of the window turns blue.
If you instead do:
<Window x:Class="WpfApp1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApp1"
mc:Ignorable="d"
Title="MainWindow" Height="200" Width="400"
Background="{StaticResource TestResourceBrush}"
>
<Window.Resources>
<SolidColorBrush x:Key="TestResourceBrush" Color="Blue"/>
</Window.Resources>
<Grid>
</Grid>
</Window>
Then that will error, saying it can't resolve the resource.
If you made that a DynamicResource, then that works ok.
<Window x:Class="WpfApp1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApp1"
mc:Ignorable="d"
Title="MainWindow" Height="200" Width="400"
Background="{DynamicResource TestResourceBrush}"
>
<Window.Resources>
<SolidColorBrush x:Key="TestResourceBrush" Color="Blue"/>
</Window.Resources>
<Grid>
</Grid>
</Window>

Answer 2

The way resources work is that the control looks for the resource in itsself, then in the parent then all the way up the visual tree until it hits the application. see here
so if you had the resource declared on a listview then the panel it is contained within can't use the resource but the list view can.
i suspect the issue you're having is that the template doesn't exist yet because you haven't compiled your code. because wpf is so flexible the designer actually has to run the code to see how it works so if your code hasn't been compiled or has changed since the last compilation the designer can't see the changes.
failing that it may just be order of execution, ie your consuming your template in an attribute but creating it in a child element, in this case move the contentTemplate to an element below the resources element and you should have access to it.
ie
<dx:ThemedWindow.Resources>
<frameworkExtensions:ConventionBasedDataTemplateSelector x:Key="dataTemplate"/>
</dx:ThemedWindow.Resources>
<dx:ThemedWindow.ContentTemplate>
<StaticResource ResourceKey="dataTemplate"/>
</dx:ThemedWindow.ContentTemplate>