DataTrigger not working on CheckBox

Question

I have the following DataTrigger in a WPF form:

<CheckBox IsChecked="{Binding ConcentratorViewModel.Integrated}">
    <CheckBox.Style>
        <Style TargetType="{x:Type CheckBox}">
            <Setter Property="Margin" Value="0,10,0,0"/>
            <Setter Property="Width" Value="20"/>
            <Setter Property="VerticalAlignment" Value="Center"/>
            <!--<Setter Property="IsEnabled" Value="False"/>-->
            <!--<Setter Property="IsChecked" Value="False"/>-->

             <Style.Triggers>
                 <DataTrigger Binding="{Binding ConcentratorViewModel.Manufacturer}" Value="ZIV">
                     <Setter Property="Background" Value="Red"/>
                     <Setter Property="IsChecked" Value="True"/>
                 </DataTrigger>

                 <DataTrigger Binding="{Binding ConcentratorViewModel.Manufacturer}" Value="Landis+Gyr">
                     <Setter Property="IsChecked" Value="False"/>                                    
                 </DataTrigger>
            </Style.Triggers>
        </Style>
    </CheckBox.Style>
</CheckBox>

The CheckBox must be Checked or Unchecked depending on the selected manufacturer. I added a converter to see the value on the trigger and it's correct. I've also added the Background property and it changes correctly, but the IsChecked doesn't work.

Viv Viv · Accepted Answer · 2013-05-23T08:55:39

Well you need to move the IsChecked Binding inside the Style. Setting it directly on the Checkbox gives it precedence and the Trigger's cannot change that value.

So something like:

<CheckBox>
  <CheckBox.Style>
    <Style TargetType="{x:Type CheckBox}">
      <Setter Property="Margin"
              Value="0,10,0,0" />
      <Setter Property="Width"
              Value="20" />
      <Setter Property="VerticalAlignment"
              Value="Center" />
      <Setter Property="IsChecked"
              Value="{Binding ConcentratorViewModel.Integrated}" />
      <Style.Triggers>
        <DataTrigger Binding="{Binding ConcentratorViewModel.Manufacturer}"
                     Value="ZIV">
          <Setter Property="Background"
                  Value="Red" />
          <Setter Property="IsChecked"
                  Value="True" />
        </DataTrigger>
        <DataTrigger Binding="{Binding ConcentratorViewModel.Manufacturer}"
                     Value="Landis+Gyr">
          <Setter Property="IsChecked"
                  Value="False" />
        </DataTrigger>
      </Style.Triggers>
    </Style>
  </CheckBox.Style>
</CheckBox>

Note:

Remember by doing this, your Binding only applies when the DataTrigger's do not evaluate to "True". Thus if your Manufacturer property is "ZIV" or "Landis+Gyr" then your Integrated property is not going to see any CheckBox updates even with a TwoWay binding as it just isn't being used.

DataTrigger not working on CheckBox

1 Answers