Code-behind for DataTemplate in a ResourceDictionary

Question

I am attempting to use code-behind to support an event handler in a DataTemplate. The below code works fine when it is the code-behind for a Window, but not for a ResourceDictionary. The code will not even compile when put in the code-behind for the ResourceDictionary.

I know that Commands is the better option here, but this is largely a test to make sure I can handle events on resources in a ResourceDictionary, if needed. My goal is to better organize my code, but this is not the straightforward "include" behavior that I thought a separate ResourceDictionary file would provide.

In MainWindow.xaml:

    <Window x:Class="Wizbang.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:my="clr-namespace:DevComponents.WpfEditors;assembly=DevComponents.WpfEditors"
        xmlns:diag="clr-namespace:System.Diagnostics;assembly=WindowsBase"
        xmlns:local ="clr-namespace:Wizbang"
        xmlns:m ="clr-namespace:Wizbang.Model"
        xmlns:vm="clr-namespace:Wizbang.ViewModel"
        xmlns:vw="clr-namespace:Wizbang.View"
        DataContext="{Binding Path=Main, Source={StaticResource Locator}}"
        Title="Wizbang" Height="760" Width="1335" WindowStartupLocation="CenterScreen">

        <Window.Resources>
            <ResourceDictionary>
                 <ResourceDictionary Source="Resources/MainWindowResources.xaml" />
            </ResourceDictionary>
        </Window.Resources>

In code-behind MainWindow.xaml.cs and MainWindowResources.xaml.cs, the same code:

private void btnSave_Click(object sender, RoutedEventArgs e)
        {
            //switch item template
            Button btn = (Button)sender;
            //command contains the list item
            ContentControl itm = (ContentControl)btn.CommandParameter;

            itm.SetValue(ContentTemplateProperty, this.FindResource("DetailedTemplate") as DataTemplate);

            //this.UpdateLayout();

        }

When I keep the ResourceDictionary inline in MainWindow.xaml, and put the code-behind in MainWindow.xaml.cs, everything works. When I attempt to use a separate file for ResourceDictionary, the code does not compile. The compiler complains about the last line:

itm.SetValue(ContentTemplateProperty, this.FindResource("DetailedTemplate") as DataTemplate);

The this.FindResource() is not a valid method, and "ContentTemplateProperty" is not found:

Error 4 The name 'ContentTemplateProperty' does not exist in the current context C:...\Visual Studio 2010\Projects\Wizbang\Wizbang\Resources\MainWindowResources.xaml.cs 36 26 Wizbang

Error 5 'Wizbang.Resources.MainWindowResources' does not contain a definition for 'FindResource' and no extension method 'FindResource' accepting a first argument of type 'Wizbang.Resources.MainWindowResources' could be found (are you missing a using directive or an assembly reference?) C:...\Visual Studio 2010\Projects\Wizbang\Wizbang\Resources\MainWindowResources.xaml.cs 36 56 Wizbang

If I remove that last line, the code compiles and runs, but the button has no functionality. I think my issue is mapping that last line's references from the perspective of a ResourceDictionary, but I am not sure why it should be different.

Thanks for any thoughts.

Bill

What does this have to do with MVVM? Seeing the [mvvm] and [codebehind] tags together makes my teeth sweat. — user1228
@Will: Even with the excellent suggestion by Erno below for handling RoutedEvents in the ViewModel, there seems to me to still be the potential need to handle some regular Events in the code-behind - even if it is some Event-to-Command sort of code. My research seems to show the consensus is that, occasionally, handling events in the code-behind is still necessary to avoid complex alternatives. So, the link to MVVM is the ability to handle Events for a DataTemplate contained in a ResourceDictionary, and be able to push the Event info to a Command in a ViewModel, if needed. — Bill

Emond Erno Emond Erno · Accepted Answer · 2011-04-12T12:00:48

3

votes

I think that using Commands would be a much cleaner approach.

Code-behind for DataTemplate in a ResourceDictionary

2 Answers