Select All Checkbox in XAML using trigger? - wpf

Question

I'd like to implement a select all checkbox in xaml.
I have several (templated) checkboxes in a listview. Then I have a checkbox outside of the listview, which I want to have a "select all"-behaviour.
I could easily solve the problem in my ViewModel, however, I think it would be more elegant to do this in xaml, since the select all checkbox doesn't (directly) have anything to do with my ViewModel.
The code looks something like this:
<ListView>
<ListView.ItemTemplate>
<DataTemplate>
<CheckBox Content="Globale Eingabe"
Name="SelectSingle"
IsChecked="{Binding IsChecked}">
</CheckBox>
</DataTemplate>
<ListView.ItemTemplate>
</ListView>
<CheckBox Name="SelectAll" />
As you see the IsChecked Property of the SelectSingle is already bound to my ViewModel. So I reckon I need a trigger to manipulate the state of the checkbox.
Now I already tried sth like this:
<CheckBox Content="Globale Eingabe"
Name="SelectSingle"
IsChecked="{Binding IsChecked}">
<CheckBox.Triggers>
<Trigger SourceName="SelectAll" Property="IsChecked" Value="True">
<Setter TargetName="SelectSingle" Property="IsChecked" Value="True"/>
</Trigger>
</CheckBox.Triggers>
</CheckBox>
or sth like this:
<CheckBox Content="Globale Eingabe"
Name="SelectSingle"
IsChecked="{Binding IsChecked}">
<CheckBox.Triggers>
<DataTrigger Binding="{Binding ElementName=SelectAll, Path=IsChecked}"
Value="True">
<Setter TargetName="Check"
Property="IsChecked"
Value="True"/>
</DataTrigger>
</CheckBox.Triggers>
</CheckBox>
I also tried the same thing within a style, but to no avail. I always obtain an error, sth along the lines of "static member "IsCheckedProperty couldn't be found in type "ContentPresenter"".
Now that sounds as if the Target/SourceName binding wouldn't work, but why?
Is there something that I am missing?

Answer 1

I think that you should put the Check All logic in the ViewModel after all. In this Code Project article, WPF Guro Josh Smith solves similar problem (in his case it's TreeView and not ListView) in the ViewModel with the following title: "Putting the Smarts in a ViewModel".
I think it'd be easier to implement and debug this logic in the ViewModel, than to do some complicated MultiBinding that you wouldn't know where it'll bite you.
Last note - I'd always follow Josh's advice :-)

Answer 2

Torsten, I am sorry if I didn't understand what you've tried already, but you need to bind the IsChecked property of the CheckBoxes inside the ListView to the IsChecked property of the CheckBox outside it using:
IsChecked="{Binding Path=IsChecked, Mode=OneWay,ElementName=OutsideCheckBox}"