Saturday, July 17, 2010

WPF ResourceDictionaries

One thing that I noticed when using WPF ResourceDictionaries (and something that I couldn’t find anywhere in any kind of documentation) is that the order in which you add items to your ResourceDictionary is important.

So if you have a DataTemplate that refers to another DataTemplate, you’ll have to put the DataTemplate you refer to first(!).

This XAML gives an error at runtime(Notice how the LinkTemplate refers to the LinkActionTemplate):

   1:  <DataTemplate x:Key="LinkTemplate">
   2:          <StackPanel VerticalAlignment="Stretch" HorizontalAlignment="Stretch" MinWidth="106" MinHeight="35" 
   3:              Cursor="Hand" Background="Transparent">
   4:              <TextBlock Text="{Binding Title}" TextWrapping="Wrap"/>
   5:              <ItemsControl ItemsSource="{Binding ChildNodes}"
   6:                  ItemTemplate="{StaticResource LinkActionTemplate}"/>
   7:          </StackPanel>
   8:  </DataTemplate>
   9:      
  10:     
  11:   <DataTemplate x:Key="LinkActionTemplate">
  12:          <StackPanel Orientation="Horizontal" Margin="20,2,0,2" MinHeight="22" Cursor="Hand">
  13:              <Image Source="{Binding IconPath}"  />
  14:              <TextBlock Text="{Binding Title}" >
  15:              </TextBlock>
  16:          </StackPanel>
  17:   </DataTemplate>
  18:      
  19:      


This XAML works fine:


   1:      <DataTemplate x:Key="LinkActionTemplate">
   2:          <StackPanel Orientation="Horizontal" Margin="20,2,0,2" MinHeight="22" Cursor="Hand">
   3:              <Image Source="{Binding IconPath}"  />
   4:              <TextBlock Text="{Binding Title}" >
   5:              </TextBlock>
   6:          </StackPanel>
   7:      </DataTemplate>
   8:   
   9:   
  10:      <DataTemplate x:Key="LinkTemplate">
  11:          <StackPanel VerticalAlignment="Stretch" HorizontalAlignment="Stretch" MinWidth="106" MinHeight="35" 
  12:              Cursor="Hand" Background="Transparent">
  13:              <TextBlock Text="{Binding Title}" TextWrapping="Wrap"/>
  14:              <ItemsControl ItemsSource="{Binding ChildNodes}"
  15:                  ItemTemplate="{StaticResource LinkActionTemplate}"/>
  16:          </StackPanel>
  17:      </DataTemplate>
  18:      

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