Question

I have a bunch of controls using identical interactions triggers across multiple user controls and viewmodels. Is it possible to place these triggers somehow into a resource dictionary for reuse? Here’s an example of what a control might look like.

       <TextBox x:Name="FirstName" Grid.Row="1" Grid.Column="1">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="KeyDown">
                    <cal:ActionMessage MethodName="KeyPressed" />
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </TextBox>

       <TextBox x:Name="Initial" Grid.Row="1" Grid.Column="1">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="KeyDown">
                    <cal:ActionMessage MethodName="KeyPressed" />
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </TextBox>

       <TextBox x:Name="LastName" Grid.Row="1" Grid.Column="1">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="KeyDown">
                    <cal:ActionMessage MethodName="KeyPressed" />
                </i:EventTrigger>
            </i:Interaction.Triggers>
        </TextBox>

The cal: namespace is from the Caliburn.Micro MVVM framework and probably isn’t relevant to this question.

Answer 1

Its not possible to re-use a single instance of Interaction.Triggers in a resource because it becomes attached a control. That attachment becomes part of its state hence a single instance can’t be shared by multiple controls.

You would need to include the Interaction.Triggers in a template so that multiple instances are created. I guess something like the following might work, (warning air code).

<UserControl.Resources>
   <DataTemplate x:key="MyTextBox">
      <TextBox>
          <i:Interaction.Triggers>
              <i:EventTrigger EventName="KeyDown">
                  <cal:ActionMessage MethodName="KeyPressed" />
              </i:EventTrigger>
          </i:Interaction.Triggers>
      </TextBox>
   </DataTemplate>
</UserControl.Resources>

…

<ContentPresenter x:Name="FirstName" Grid.Row="1" Grid.Column="1" ContentTemplate="{StaticResource MyTextBox}" />
<ContentPresenter x:Name="Initial" Grid.Row="1" Grid.Column="1" ContentTemplate="{StaticResource MyTextBox}" />
<ContentPresenter x:Name="LastName" Grid.Row="1" Grid.Column="1" ContentTemplate="{StaticResource MyTextBox}" />

It my opinion that this sort of stuff isn’t worth it. The Interaction Triggers stuff is really aimed at empowering the designer rather than the developer. A designer isn’t that worried that there is some repeatition in the “code”.