# Using Avalonia Collectionview

> Provides CollectionView alternatives for AvaloniaUI using DataGridCollectionView and ReactiveUI. Use when filtering, sorting, or grouping collections in AvaloniaUI applications.

- Skill: `tomevault-io/using-avalonia-collectionview` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/using-avalonia-collectionview`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/using-avalonia-collectionview/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/using-avalonia-collectionview

---


# 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)

```csharp
// 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)

```csharp
// 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);
}
```

---
> Converted and distributed by [TomeVault](https://tomevault.io/claim/christian289) — claim your Tome and manage your conversions.
<!-- tomevault:4.0:skill_md:2026-04-11 -->