6.7 MVVM Pattern with CollectionView

⚠️ Important: AvaloniaUI does not support WPF's CollectionViewSource.

Project Structure

The templates folder contains a .NET 9 AvaloniaUI project example.

templates/ ├── AvaloniaCollectionViewSample.Core/ ← Pure C# models and interfaces │ ├── Member.cs │ ├── IMemberCollectionService.cs │ └── AvaloniaCollectionViewSample.Core.csproj ├── AvaloniaCollectionViewSample.ViewModels/ ← ViewModel (no Avalonia references) │ ├── MainViewModel.cs │ ├── GlobalUsings.cs │ └── AvaloniaCollectionViewSample.ViewModels.csproj ├── AvaloniaCollectionViewSample.AvaloniaServices/ ← Avalonia Service Layer │ ├── MemberCollectionService.cs │ ├── GlobalUsings.cs │ └── AvaloniaCollectionViewSample.AvaloniaServices.csproj └── AvaloniaCollectionViewSample.App/ ← Avalonia Application ├── Views/ │ ├── MainWindow.axaml │ └── MainWindow.axaml.cs ├── App.axaml ├── App.axaml.cs ├── Program.cs ├── GlobalUsings.cs └── AvaloniaCollectionViewSample.App.csproj

In AvaloniaUI, use the following approaches:

6.7.1 Using DataGridCollectionView (Recommended)

// NuGet: Avalonia.Controls.DataGrid // Service Layer namespace MyApp.Services;

using Avalonia.Controls;

public sealed class MemberCollectionService { private ObservableCollection<Member> Source { get; } = [];

// Returns DataGridCollectionView
public IEnumerable CreateView(Predicate<Member>? filter = null)
{
    var view = new DataGridCollectionView(Source);

    if (filter is not null)
    {
        view.Filter = item => filter((Member)item);
    }

    return view;
}

public void Add(Member item) => Source.Add(item);
public void Remove(Member? item) { if (item is not null) Source.Remove(item); }
public void Clear() => Source.Clear();

}

6.7.2 Using ReactiveUI (Alternative)

// NuGet: ReactiveUI.Avalonia namespace MyApp.ViewModels;

using ReactiveUI; using DynamicData;

public sealed class MainViewModel : ReactiveObject { private readonly SourceList<Member> _sourceList = new(); private readonly ReadOnlyObservableCollection<Member> _members;

public ReadOnlyObservableCollection<Member> Members => _members;

public MainViewModel()
{
    _sourceList
        .Connect()
        .Filter(m => m.IsActive) // Filtering
        .Sort(SortExpressionComparer<Member>.Ascending(m => m.Name)) // Sorting
        .Bind(out _members)
        .Subscribe();
}

public void AddMember(Member member) => _sourceList.Add(member);
public void RemoveMember(Member member) => _sourceList.Remove(member);

}