Question

I have a view in XAML where I have a listbox, and a selection in that listbox populates an area to the side with properties from the selected instance of the ChildViewModel. I have a few buttons in the ChildView that are connected to commands in the ChildViewModel. Before I make a selection from the parent listbox, these buttons do nothing as expected. How could I keep these buttons hidden until a selection selection in the parent listbox is made, thus creating an instance of the ChildViewModel.

I know how I could accomplish this if these buttons were part of the parent view by binding the visibility of these buttons to {Binding SelectedItem, ElementName=listBoxName}. However, I am having a hard time accomplishing this within the ChildView because I do not have access to (and do not want to be dependent on) the element from the parent view. Please help me accomplish this, preferably purely within the XAML code.

Answer 1

You should be able to just check if the datacontext of the childview is null (i.e. no ChildViewModel set). If it is null hide the buttons.

<Button Click="Button_Click" Content="bah">
        <Button.Style>
            <Style TargetType="Button">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding RelativeSource={RelativeSource AncestorType=Window, Mode=FindAncestor}, Path=DataContext}" Value="{x:Null}" >
                        <Setter Property="Visibility" Value="Collapsed"/>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Button.Style>
    </Button>

Set the ancestor to whatever container is holding your child view