MVVM Nested databinding

Question

I'm having some trouble with databinding inside a UserControl when using an ItemsControl which has an ItemsSource. My Eventtrigger is never called.

I Think the problem is that when I call my eventtrigger in the line:

<cmd:EventToCommand Command="{Binding ElementName=layoutroot, Path=DataContext.Checked}" />

it tries to find the checked event in CheckBoxes collection because i have set my ItemsSource, while it should be looking in its parent . I've been searching for a solution for days, but none of them seem to work.

My code looks like this:

<Grid x:Name="layoutroot">
            <ItemsControl x:Name="itemcontrol" ItemsSource="{Binding CheckBoxes}">
                <ItemsControl.ItemsPanel>
                    <ItemsPanelTemplate>
                        <StackPanel Orientation="Vertical"></StackPanel>
                    </ItemsPanelTemplate>
                </ItemsControl.ItemsPanel>
                <ItemsControl.ItemTemplate>
                    <DataTemplate>
                        <s:SurfaceCheckBox Background="White" Foreground="White">
                            <i:Interaction.Triggers>
                                <i:EventTrigger EventName="Checked">
                                    <cmd:EventToCommand Command="{Binding ElementName=layoutroot, Path=DataContext.Checked}" />
                                </i:EventTrigger>
                            </i:Interaction.Triggers>
                        </s:SurfaceCheckBox>
                    </DataTemplate>
                </ItemsControl.ItemTemplate>
            </ItemsControl>
        </Grid>

When I try the following code it works exactly as expected:

<Grid x:Name="layoutroot">
    <s:SurfaceCheckBox Background="White" Foreground="White" Content="{Binding Content}" >
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="Checked">
                <cmd:EventToCommand Command="{Binding ElementName=layoutroot, Path=DataContext.Checked}" />
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </s:SurfaceCheckBox>
</Grid>

But I really need this behaviour inside an itemsControl with a set ItemsSource.

Any ideas?

Answer 1

Binding inside of an ItemsControl is placed upon the current Item in the collection. What you need to do is seek out the parent, and Bind from there.

Give this a try from inside your ItemsControl, replacing MyUserControlName:

<cmd:EventToCommand Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:MyUserControlName} }, Path=DataContext.Checked}" />