WPF TreeView Nodes becomes unselectable after adding children nodes

Question

I have a huge issue with the WPF TreeView. I have setup a tree that is similar to this.

<TreeView DataContext="{Binding Projects}">
    <Style TargetType="TreeViewItem">
        <Setter Property="IsExpanded" Value="True" />
    </Style>
    <TreeView.Resources>
        <HierarchicalDataTemplate x:Key="LoadTemplate">
            <Grid>
                <TextBlock Text="{Binding Name}" />
            </Grid>
        </HierarchicalDataTemplate>
        <HierarchicalDataTemplate x:Key="StepTemplate"
                ItemsSource="{Binding Loads}" 
                ItemTemplate="{StaticResource LoadTemplate}">
            <Grid>
                <TextBlock Text="{Binding Name}" />
            </Grid>
        </HierarchicalDataTemplate>
        <HierarchicalDataTemplate x:Key="ProjectTemplate"
                ItemsSource="{Binding Steps}"
                ItemTemplate="{StaticResource StepTemplate}">
            <Grid>
                <TextBlock Text="{Binding Name}" />
            </Grid>
        </HierarchicalDataTemplate>
    </TreeView.Resources>
    <TreeViewItem Header="Project Workspace"
            ItemsSource="{Binding}"
            IsExpanded="True"
            ItemTemplate="{StaticResource ProjectTemplate}" />
</TreeView>

The TreeView is bound to a DependencyProperty called Projects which is an ObservableCollection in the code-behind file for the xaml. The basic structure of the classes that the tree is bound to follows the structure of the tree. So Project contains a custom collection that implements both the INotifyPropertyChanged and ICollectionChanged interfaces. That collection is accessible through a property called Steps and contains Step objects. The Step class also has an instance of the same custom collection accessable from a property called Loads and contains Load objects.

Now when I work with any object within the Projects, the tree behaves correctly in that nodes appear and dissappear and change correctly as the set of nested collections change. For the most part, everything works as it should.

Althought I didn't show it in the Xaml above, each of the nodes above have their own specific context menu added. One of the options in that context menu is to add an object. So for instance, if you right click on a Step node, you have the option to add a Load node beneath it. Adding the Load class into the Loads property in the Step object does cause a node to show up in the tree just fine.

So for instance the code looks something similar to this:

Projects[0].Steps[0].Loads.add(new Load());

Ok, here is the problem that I've been trying to figure out for the longest time now. After that new node shows up in the tree, it's parent node is no longer selectable. So in the given example, you cannot select the Step node that owns the newly added Load node. You can still do things like DoubleClick and RightClick and get events to fire, but simply attepting to single click with the left mouse button will not cause the Step node to be selected or have focus. I've tried everything I can think of and I cannot for the life of me figure out why not.

Now I can click around on other nodes in the tree and they are selecatable just fine. And after doing so, the node that previously would not allow being selected then regains it's former functionality and is once again able to be selected.

So what happens is that you add a new node, it shows up and it's parent can't be selected until you select some other part of the TreeView and then everything is fine again.

Answer 1

With no help and nothing I tried having worked, I switched to using Telerik controls. After replacing the default TreeView with the RadTreeView from Telerik, all my issues disappeared. I'd suggest if possible that people avoid Microsoft's built in WPF TreeView control as it is plagued with countless issues and you'll spend a great amounts of time trying to deal with them, rather than developing your application.