SourceName with MultiTriggers

Question

Is it possible to use a multiTrigger to evaluate properties on multiple elements? That don't reside within a template, but are within the Usercontrol/Window.

Example:

<CheckBox x:Name="checkBox1" />
<CheckBox x:Name="checkBox2" />

<CustomControl>
   <CustomControl.ContentTemplate>
              <DataTemplate>
                        <DataTemplate.Triggers>
                            <MultiTrigger>
                                <MultiTrigger.Conditions>
                                    <Condition
                                        SourceName="checkBox1"
                                        Property="IsChecked"
                                        Value="False" />
                                    <Condition
                                        SourceName="checkBox2"
                                        Property="IsChecked"
                                        Value="True" />
                                </MultiTrigger.Conditions>
                                <MultiTrigger.Setters>
                                    <Setter
                                        Property="Visibility"
                                        Value="Collapsed" />
                                </MultiTrigger.Setters>
                            </MultiTrigger>
                        </DataTemplate.Triggers>
                    </DataTemplate>
</CustomControl.ContentTemplate>

In a normal Trigger we can use the sourceName to trigger against properties on either of those checkbox controls, but with a multiTrigger I get build errors when it attempts to find those controls.

Note: The reason I'm using a DataTemplate as opposed to a Style is mentioned here

Answer 1

You can indeed use source name, but your DataTemplate doesn't appear to be defined correctly. I've tried filling out your example which seems to work:

<Page
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:sys="clr-namespace:System;assembly=mscorlib">
    <Grid>
     <Grid.Resources>
      <DataTemplate DataType="{x:Type sys:String}">
       <StackPanel>
        <TextBlock x:Name="textBlock" Text="{Binding}"></TextBlock>
        <CheckBox x:Name="checkBox1" />
        <CheckBox x:Name="checkBox2" />
       </StackPanel>
       <DataTemplate.Triggers>
        <MultiTrigger>
         <MultiTrigger.Conditions>
          <Condition
           SourceName="checkBox1"
           Property="IsChecked"
           Value="False" />
          <Condition
           SourceName="checkBox2"
           Property="IsChecked"
           Value="True" />
         </MultiTrigger.Conditions>
         <MultiTrigger.Setters>
          <Setter
          TargetName="textBlock"
           Property="Visibility"
           Value="Collapsed" />
         </MultiTrigger.Setters>
        </MultiTrigger>
       </DataTemplate.Triggers>

      </DataTemplate>
     </Grid.Resources>
     <ContentControl>
      <sys:String>Foo</sys:String>
     </ContentControl>
    </Grid>
</Page>

The problem appears to be that you don't define your CheckBoxes inside your DataTemplate, which is where they need to be.