How to use style from resource dictionary in Custom Control Library project

Question

I have created a project of type "WPF Custom Control Library" (.Net Core 3.1) and a resource dictionary named "GResourceDic" with the following content:

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">  
  
    <Style x:Key="BorderStyle" TargetType="{x:Type Border}">  
        <Setter Property="BorderThickness" Value="1"/>  
        <Setter Property="BorderBrush" Value="AliceBlue"/>  
        <Setter Property="VerticalAlignment" Value="Stretch"/>  
        <Setter Property="Background" Value="Beige"/>  
    </Style>  
  
</ResourceDictionary>  

In Generic.xaml I have added the following:

<ResourceDictionary  
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  
    xmlns:local="clr-namespace:Common">  
    <Style TargetType="{x:Type local:CustomControl1}">  
        <Setter Property="Template">  
            <Setter.Value>  
                <ControlTemplate TargetType="{x:Type local:CustomControl1}">  
                    <Border Background="{TemplateBinding Background}"  
                            BorderBrush="{TemplateBinding BorderBrush}"  
                            BorderThickness="{TemplateBinding BorderThickness}">  
                    </Border>  
                </ControlTemplate>  
            </Setter.Value>  
        </Setter>  
    </Style>  
  
    <ResourceDictionary.MergedDictionaries>  
        <ResourceDictionary Source="ResourceDics/GResourceDic.xaml"/>  
    </ResourceDictionary.MergedDictionaries>  
  
</ResourceDictionary>  

I then created a Window:

<UserControl x:Class="Common.BarView"  
             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"   
             mc:Ignorable="d"   
             d:DesignHeight="50"  
             d:DesignWidth="700">  
      
      
    <Grid>  
        <Border Style="{StaticResource BorderStyle}"/>  
    </Grid>  
</UserControl>  

<Window x:Class="Common.ActView"  
        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:Common"  
        mc:Ignorable="d"  
        WindowStartupLocation="CenterScreen"   
        Background="White"  
        WindowStyle="None"  
        Height="210"  
        Width="450" >  
  
  
    <Grid>  
        <Grid.RowDefinitions >  
            <RowDefinition Height="30"/>  
            <RowDefinition Height="*"/>  
        </Grid.RowDefinitions>  
  
        <local:MenuBarView Grid.Row="0"/>  
  
        <Grid Grid.Row="1"  
              Margin="20">  
  
            <Border Style="{StaticResource BorderStyle}"/>  
        </Grid>  
  
    </Grid>  
</Window>  

I always get the following Felhler:

Error XDG0062 The resource "BorderStyle" could not be resolved.

Answer 1

On the one hand:

WPF is unable to resolve the resource dictionary that you are trying to merge. When you create a merged dictionary, WPF follows a set of rules to attempt to resolve the URI. In your case, the URI is ambiguous, so WPF is unable to reliably resolve it.

Change the Source URI in the ResourceDictionary to an absolute pack URI.

For example, if your project is called Common, then you could change the Source in GResourceDic.xaml to:

   <ResourceDictionary Source="Common;component/ResourceDics/GResourceDic.xaml" />  

See this page on MSDN for further details on Pack URIs in WPF.

On the other hand:
ResourceDictionary needs to be in Resources. You can delete the ResourceDictionary in Generic.xaml. Add the following code in UserControl(BarView:UserControl.Resources ) and Window(ActView: Window.Resources ) respectively.

< Window.Resources>   
<ResourceDictionary>  
  <ResourceDictionary.MergedDictionaries>  
    <ResourceDictionary Source="Commen;component/ResourceDics/GResourceDic.xaml" />  
  </ResourceDictionary.MergedDictionaries>  
</ResourceDictionary>  
< / Window.Resources>  

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