Question

I have a container view that looks something like this

<UserControl x:Class="Views.ContainerView">
    <UserControl.Resources>
        <ResourceDictionary>
            <DataTemplate DataType="{x:Type viewmodels:AViewModel}">
                <views:MyView />
            </DataTemplate>
            <DataTemplate DataType="{x:Type viewmodels:BViewModel}">
                <views:MyView />
            </DataTemplate>
            <DataTemplate DataType="{x:Type viewmodels:CViewModel}">
                <views:MyView />
            </DataTemplate>
            <DataTemplate DataType="{x:Type viewmodels:DViewModel}">
                <views:MyView />
            </DataTemplate>
        </ResourceDictionary>
    </UserControl.Resources>
    <Grid>
        <ListBox ItemsSource="{Binding Path=AvailableViewModels}" 
            SelectedItem="{Binding Path=CurrentViewModel}" 
            IsSynchronizedWithCurrentItem="True" />
        <ContentControl Content="{Binding Path=CurrentViewModel}" />
    </Grid>
</UserControl>

All my viewmodels inherit BaseViewModel so I turned my view into this

<UserControl x:Class="Views.ContainerView">
    <UserControl.Resources>
        <ResourceDictionary>
            <DataTemplate DataType="{x:Type viewmodels:BaseViewModel}">
                <views:MyView />
            </DataTemplate>
        </ResourceDictionary>
    </UserControl.Resources>
    <StackPanel>
        <ListBox ItemsSource="{Binding Path=AvailableViewModels}" 
            SelectedItem="{Binding Path=CurrentViewModel}" 
            IsSynchronizedWithCurrentItem="True" />
        <ContentControl Content="{Binding Path=CurrentViewModel}" />
    </StackPanel>
</UserControl>

thinking it would instantiate just a single MyView and just rebind the viewmodel when ListBox.SelectedItem changes. Am I understanding this behavior correctly? Is this a preferred practice? How can I verify that I’m not churning memory as I switch between views?

Answer 1

It will instantiate a new MyView for each view model you use. If you want to reuse your user controls, you can set the DataContext property on each user control.