Use different datatemplate by binding to different TreeView selectedItem

Question

I have built a WPF MVVM TreeView that shows different Elements.

BaseElement
- CatA
-- SubItemA
- CatB
-- SubItemB

Based on the class I would like to use a different data template. for each type.

So far I can connect to the selected Item, but I'm not sure how to manage the different data templates.

public class SubItem
{
    public string Type { get; set; }
    public string Name { get; set; }
}

    <StackPanel Grid.Column="2" DataContext="{Binding ElementName=myTreeView, Path=SelectedItem}">
        <TextBox Text="{Binding Parent.Name}" />
        <TextBox Text="{Binding Path=Name, Mode=TwoWay}" />
    </StackPanel>

[Update Nov. 15]

           <HierarchicalDataTemplate x:Key="L3Template" ItemsSource="{Binding L4Collection}" ItemTemplate="{StaticResource L4Template}">
                <StackPanel Orientation="Horizontal">
                    <TextBlock Text="{Binding Name}" />
                </StackPanel>
            </HierarchicalDataTemplate>

            <HierarchicalDataTemplate x:Key="CategoryTemplate" ItemsSource="{Binding L3Collection}" ItemTemplate="{StaticResource L3Template}">
                <StackPanel>
                    <TextBlock Text="{Binding Name}" />
                </StackPanel>
            </HierarchicalDataTemplate>

            <HierarchicalDataTemplate x:Key="L1Template" ItemsSource="{Binding CategoryCollection}" ItemTemplate="{StaticResource CategoryTemplate}">
                <StackPanel>
                    <TextBlock Text="{Binding Name}" />
                </StackPanel>
            </HierarchicalDataTemplate>

[/Update Nov. 15]

Answer 1

If the subitems are different classes, then it is rather simple: add datatemplates foreach class to the resource section. If subitems need different templates based on the value of an enum prop, then you will need a datatemplateselector. This is a bit more cumbersome.

Answer 2

Assuming that you named your classes L1Class, L3Class en Category and local points to the namespace of these classes:

    <TreeView ...>
        <TreeView.Resources>
                <HierarchicalDataTemplate DataType="{x:Type local:L3Class}" ItemsSource="{Binding L4Collection}" >
                    <StackPanel Orientation="Horizontal">
                        <TextBlock Text="{Binding Name}" />
                    </StackPanel>
                </HierarchicalDataTemplate>

                <HierarchicalDataTemplate DataType="{x:Type local:Category}" ItemsSource="{Binding L3Collection}" >
                    <StackPanel>
                        <TextBlock Text="{Binding Name}" />
                    </StackPanel>
                </HierarchicalDataTemplate>

                <HierarchicalDataTemplate DataType="{x:Type local:L1Class}" ItemsSource="{Binding CategoryCollection}" >
                    <StackPanel>
                        <TextBlock Text="{Binding Name}" />
                    </StackPanel>
                </HierarchicalDataTemplate>
            </TreeView.Resources>
    </TreeView>

Note the use of the implicit datatemplates (no keys, but DataType!) in the resource section.

Answer 3

Just in case it will help someone else:

        <ContentPresenter Grid.Column="2" Content="{Binding ElementName=myTreeView, Path=SelectedItem}">
            <ContentPresenter.Resources>
                <DataTemplate DataType="{x:Type local:L1ViewModel}">
                    <StackPanel>
                        <TextBlock Text="{Binding Name}" />
                    </StackPanel>
                </DataTemplate>
                <DataTemplate DataType="{x:Type local:CategoryViewModel}">
                    <StackPanel>
                        <TextBlock Text="{Binding Name}" />
                    </StackPanel>
                </DataTemplate>

                <DataTemplate DataType="{x:Type local:L3ViewModel}">
                    <StackPanel>
                        <TextBlock Text="{Binding Name}" />
                    </StackPanel>
                </DataTemplate>

                <DataTemplate DataType="{x:Type local:L4ViewModel}">
                    <StackPanel>
                         <TextBox Text="{Binding Parent.Name}" />
                        <TextBlock Text="{Binding Name}" />
                    </StackPanel>
                </DataTemplate>
            </ContentPresenter.Resources>
          </ContentPresenter>