Question

in order to clean up my code, I’m trying to split my app.xaml into seperate resource dictionaries. This works at runtime, but not at design time:

snipped in app.xaml

    <Application.Resources>
      <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="/;component/Theme/Colors.xaml" />
            <ResourceDictionary Source="/;component/Theme/Styles.xaml" />
        </ResourceDictionary.MergedDictionaries>
      </ResourceDictionary>
    </Application.Resources>

Colors.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

  <SolidColorBrush x:Key="backgroundBrush" Color="Gold"/>
</ResourceDictionary>

Styles.xaml

    <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

      <Style TargetType="StatusBar">
        <Setter Property="Background" Value="{StaticResource backgroundBrush}" />
      </Style>
    </ResourceDictionary>

Snipped of MainWindow.xaml

<Window x:Class="test.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="test" Width="800" Height="600" >
    <StatusBar Name="statusBar" DockPanel.Dock="Bottom">
        <StatusBarItem Content="{Binding statusMessage}" />
    </StatusBar>

DesignView gives the error:
Error 8 ‘{DependencyProperty.UnsetValue}’ is not a valid value for property ‘Background’. C:\Daten\DotNet\test\test\MainWindow.xaml 123

If I put backgroundBrush directly into app.xaml like so:

    <Application.Resources>
      <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="/;component/Theme/Colors.xaml" />
            <ResourceDictionary Source="/;component/Theme/Styles.xaml" />
            <ResourceDictionary>
                <SolidColorBrush x:Key="backgroundBrush" Color="Gold"/>
            </ResourceDictionary>
        </ResourceDictionary.MergedDictionaries>
      </ResourceDictionary>
    </Application.Resources>

DesignView has no problems.

So is there a way to tell DesignView where to find backgroundBrush, if this brush is placed into a seperate resource dictionary?

Answer 1

Thats the problem with StaticResource isnt it. It needs the resource key resolved explicitly using shared \ merged \ direct resource dictionaries hierarchically up.

There are two options…

merge Colors.xaml dictionary in Styles.xaml

OR

in Styles.xaml refer the bursh using DynamicResource.