Quickstart: Flat TreeDataGrid

This quickstart builds a complete flat (non-hierarchical) TreeDataGrid with editable text columns.

Goal

Create a window showing a list of people with columns:

First Name
Last Name
Age

1. Data Model

Create Person.cs:

public class Person
{
    public string? FirstName { get; set; }
    public string? LastName { get; set; }
    public int Age { get; set; }
}

2. View Model with Flat Source

Create MainWindowViewModel.cs:

using System.Collections.ObjectModel;
using Avalonia.Controls;
using Avalonia.Controls.Models.TreeDataGrid;

public class MainWindowViewModel
{
    private readonly ObservableCollection<Person> _people = new()
    {
        new Person { FirstName = "Eleanor", LastName = "Pope", Age = 32 },
        new Person { FirstName = "Jeremy", LastName = "Navarro", Age = 74 },
        new Person { FirstName = "Lailah", LastName = "Velazquez", Age = 16 },
        new Person { FirstName = "Jazmine", LastName = "Schroeder", Age = 52 },
    };

    public MainWindowViewModel()
    {
        Source = new FlatTreeDataGridSource<Person>(_people)
        {
            Columns =
            {
                new TextColumn<Person, string>(
                    "First Name",
                    x => x.FirstName,
                    (m, v) => m.FirstName = v),
                new TextColumn<Person, string>(
                    "Last Name",
                    x => x.LastName,
                    (m, v) => m.LastName = v),
                new TextColumn<Person, int>(
                    "Age",
                    x => x.Age,
                    (m, v) => m.Age = v ?? 0),
            },
        };

        // Optional: enable multiple row selection.
        Source.RowSelection!.SingleSelect = false;
    }

    public FlatTreeDataGridSource<Person> Source { get; }
}

Notes:

FlatTreeDataGridSource<TModel> is the root source object.
Each column is strongly typed and binds to model properties.
Setter overloads make text cells editable.

3. Bind in XAML

Update MainWindow.axaml:

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        x:Class="AvaloniaApplication.MainWindow">
  <TreeDataGrid Source="{Binding Source}" />
</Window>

4. Set DataContext

Update MainWindow.axaml.cs:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        DataContext = new MainWindowViewModel();
    }
}

5. Run

Start the app and verify data appears:

Simple TreeDataGrid

What You Have Now

A fully bound flat TreeDataGrid
Editable text cells
Optional multi-row selection

Common Next Steps

Add CheckBoxColumn and TemplateColumn
Configure sorting and widths
Switch to cell selection

Troubleshooting

Feature behavior differs from expectations Cause: one or more options in this scenario are configured differently (source type, column options, sort/selection/edit state). Fix: compare your setup with the snippet in this article and verify runtime values on Source, Columns, and Selection.
Data changes are not visible in UI Cause: model or collection notifications are missing, or a replaced collection/source is not re-bound. Fix: ensure INotifyPropertyChanged/INotifyCollectionChanged flow is active and reassign Source after replacing underlying collections.