How to set default IsChecked value for Silverlight ToggleButton

Question

I have a Toggle button defined in a style for a Silverlight TreeviewItem, and I would like it to start off in the IsChecked=true state. I tried simply setting IsChecked=True, but that has no effect.

Thanks

Example XAML:

<Style x:Name="CheckedToggleButton"
       TargetType="ToggleButton">
    <Setter Property="IsChecked"
            Value="True" />
    <Setter Property="Margin"
            Value="0" />
</Style>

<Style x:Key="TreeViewItemStyle"
       TargetType="controls:TreeViewItem">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="controls:TreeViewItem">
                <Grid Margin="2">
                    <Grid.RowDefinitions>
                        <!--ContentPresenter Row-->
                        <RowDefinition Height="Auto" />
                        <!--ExpanderButton Row-->
                        <RowDefinition Height="Auto" />
                        <!--ItemsPresenter Row-->
                        <RowDefinition Height="*" />
                    </Grid.RowDefinitions>
                    <ContentPresenter Cursor="{TemplateBinding Cursor}"
                                      HorizontalAlignment="Stretch"
                                      Margin="{TemplateBinding Padding}"
                                      x:Name="content"
                                      Content="{TemplateBinding Header}"
                                      ContentTemplate="{TemplateBinding HeaderTemplate}"
                                      Grid.RowSpan="1"/>
                    <ToggleButton x:Name="ExpanderButton"
                                  Style="{StaticResource CheckedToggleButton}"
                                  IsChecked="True"
                                  HorizontalAlignment="Center"
                                  VerticalAlignment="Bottom"
                                  Width="15"
                                  Height="15"
                                  Grid.Row="1" />
                    <ItemsPresenter x:Name="ItemsHost"
                                    Visibility="{Binding ElementName=ExpanderButton, Path=IsChecked, Converter={StaticResource boolviz}}"
                                    Grid.Row="2"
                                    HorizontalAlignment="Stretch" />
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

AnthonyWJones AnthonyWJones · Accepted Answer · 2011-03-30T20:33:44

I very much expect that the code in the TreeviewItem class will be specifically assigning a the IsChecked depending on the state of is own IsExpanded property.

Try adding another setter to your style:-

 <Setter Property="IsExpanded" Value="True" />

This should put the TreeViewItem in an expanded state by default and will likely cause the TreeviewItem to set the ExpanderButton IsChecked to true at the same time.

How to set default IsChecked value for Silverlight ToggleButton

2 Answers