Use checkbox as togglebutton in expander

Question

Im quite new to wpf and have to following problem.

I need to create a List (i am using a listbox) of items that can be expanded (expander). The problem is, that they can be expanded, only if they have been 'selected'. Each listboxitem should have a checkbox and some text.

So very basic example to illustrate what i mean:

<listbox>
<item>(checkbox) John Doe</item>
<item>(checkbox) Mike Murray</item>
</listbox>

If any (so multiple is allowed) of the checkboxes in the listbox are checked, then the item expands showing more data.

Again an example:

<listbox>
<item>
   (checkbox-checked) John Doe
   Some extra data shown in expanded area
</item>
<item>
   (checkbox-unchecked) Mike Murray</item>
</listbox>

I cant get a expander to use a checkbox as 'togglebutton'.

Could anyone help me out? Some example code would be very welcome...

Answer 1

This should do the trick:

<ListBox>
    <ListBox.Resources>
        <Style TargetType="Expander">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Expander">
                        <Grid>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto" />
                                <RowDefinition Height="Auto" />
                            </Grid.RowDefinitions>

                            <CheckBox
                                IsChecked="{Binding Path=IsExpanded, RelativeSource={RelativeSource TemplatedParent}}"
                                Content="{TemplateBinding Header}"
                                />
                            <ContentControl
                                x:Name="body"
                                Grid.Row="1" Content="{TemplateBinding Content}"
                                />
                        </Grid>

                        <ControlTemplate.Triggers>
                            <Trigger Property="IsExpanded" Value="False">
                                <Setter TargetName="body" Property="Visibility" Value="Collapsed" />
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>

    </ListBox.Resources>

    <Expander Header="One">
        Content one
    </Expander>

    <Expander Header="Two">
        Content two
    </Expander>
</ListBox>

I've defined a Style here that changes the Template of any Expander controls to which the Style is applied. (And since I've put the Style in the ListBox.Resources it'll automatically apply to an Expander controls in the list.)

The trick to getting the CheckBox to work is that when you put it (or indeed any ToggleButton based control) into an Expander template, you need to use a data binding configured with its RelativeSource set to the TemplatedParent. This enables two-way binding - it means that not only does the CheckBox reflect the current state of the expander, it is also able to change the current state.

Answer 2

All you need to add a check box in the header is this code:

            <telerik:RadExpander.Header>
                <StackPanel Orientation="Horizontal">
                    <CheckBox VerticalAlignment="Center"/>
                    <TextBlock Margin="5,0,0,0">Legend</TextBlock>
                </StackPanel>
            </telerik:RadExpander.Header>

I am using Rad Control, The same can be done using the standard expander