Home/ Questions/Q 4038230
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-20T12:26:50+00:00

I have an application which I am trying to design using the MVVM pattern.

  • 0

I have an application which I am trying to design using the MVVM pattern. In my Models I have Group and Case. A Group may contain other groups as well as cases. Now, I want to display these in a TreeView in my View. So because Groups may contain other groups and cases, the tree can end up looking something like this:
Group
—Group
—-Case
—-Case
—Group
—-Group
—-Case
—Case
Case

I have my View attached to a ViewModel which contains an ObservableCollection of Groups. My problem is that the only way I can get the TreeView to display as I would like it to is to use a HierarchicalDataTemplate in the resources pointed to the datatype (Group or Case), which I feel like is breaking MVVM (where the View should not know about the Model).

This works:

 <UserControl.Resources>
    <HierarchicalDataTemplate DataType="{x:Type models:Group}" ItemsSource="{Binding Children}">
        <TextBlock Text="{Binding GroupName}" />
    </HierarchicalDataTemplate>
    <DataTemplate DataType="{x:Type models:Case}">
        <TextBlock Text="{Binding CaseName}" />
    </DataTemplate>
</UserControl.Resources>

and for the TreeView:

<TreeView ItemsSource="{Binding AvailableCaseGroups}" />

Is this breaking the spirit of MVVM? How can I do this otherwise?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    I don’t think it’s breaking MVVM at all, if the View knows about the ViewModel.
    Surely, using Model details in the View is not fine with MVVM.
    To work around this you could just build up some hierarchical structure of ViewModels – MainViewModel
    — GroupViewModel g1
    —GroupViewModel g1a
    —CaseViewModel c1b
    — GroupVieModel g2
    …
    Then it’s no longer a structural detail of your Model but one of your ViewModel and can be used by the View. If the Model may structurally change in the future, become a flat list or s.th., your ViewModel can still stick to the old hierarchy (transform the Model) and your View is still valid.

    • 0