diff --git a/TreeDataGrid/FlatTreeDataGridSample/FlatTreeDataGridSample.csproj b/TreeDataGrid/FlatTreeDataGridSample/FlatTreeDataGridSample.csproj
index bfd200b..dae1ebe 100644
--- a/TreeDataGrid/FlatTreeDataGridSample/FlatTreeDataGridSample.csproj
+++ b/TreeDataGrid/FlatTreeDataGridSample/FlatTreeDataGridSample.csproj
@@ -14,7 +14,7 @@
 
   <ItemGroup>
     <PackageReference Include="Avalonia" Version="$(AvaloniaVersion)" />
-    <PackageReference Include="Avalonia.Controls.TreeDataGrid" Version="11.2.0" />
+    <PackageReference Include="Avalonia.Controls.TreeDataGrid" Version="11.3.0-beta4" />
     <PackageReference Include="Avalonia.Desktop" Version="$(AvaloniaVersion)" />
     <PackageReference Include="Avalonia.Themes.Fluent" Version="$(AvaloniaVersion)" />
     <PackageReference Include="Avalonia.Fonts.Inter" Version="$(AvaloniaVersion)" />
diff --git a/TreeDataGrid/FlatTreeDataGridSample/ViewModels/MainWindowViewModel.cs b/TreeDataGrid/FlatTreeDataGridSample/ViewModels/MainWindowViewModel.cs
index 536051b..d427b3b 100644
--- a/TreeDataGrid/FlatTreeDataGridSample/ViewModels/MainWindowViewModel.cs
+++ b/TreeDataGrid/FlatTreeDataGridSample/ViewModels/MainWindowViewModel.cs
@@ -2,6 +2,7 @@
 using System.Linq;
 using Avalonia.Controls;
 using Avalonia.Controls.Models.TreeDataGrid;
+using Avalonia.Controls.Selection;
 using FlatTreeDataGridSample.Models;
 
 namespace FlatTreeDataGridSample.ViewModels;
@@ -26,6 +27,11 @@ public MainWindowViewModel()
         {
             Columns =
             {
+                // Define a row header column for row numbering. This can be made to be always
+                // visible when scrolling horizontally by setting FrozenColumnCount = 1 on the
+                // TreeDataGrid.
+                new RowHeaderColumn<Country>(),
+
                 // Define a read/write text column for the country name with text search enabled.
                 new TextColumn<Country, string>(
                     "Country",
@@ -52,6 +58,7 @@ public MainWindowViewModel()
             }
         };
 
+        Source.Selection = new TreeDataGridCellSelectionModel<Country>(Source);
         MaxPopulation = _data.Max(x => x.Population);
     }
 
diff --git a/TreeDataGrid/FlatTreeDataGridSample/Views/MainWindow.axaml b/TreeDataGrid/FlatTreeDataGridSample/Views/MainWindow.axaml
index e6d4c96..406bbcf 100644
--- a/TreeDataGrid/FlatTreeDataGridSample/Views/MainWindow.axaml
+++ b/TreeDataGrid/FlatTreeDataGridSample/Views/MainWindow.axaml
@@ -18,6 +18,7 @@
                 Source="{Binding Source}"
                 AllowTriStateSorting="True"
                 AutoDragDropRows="True"
+                FrozenColumnCount="1"
                 CellPrepared="countries_CellPrepared"
                 CellClearing="countries_CellClearing">
     <TreeDataGrid.Resources>
diff --git a/TreeDataGrid/FlatTreeDataGridSample/readme.md b/TreeDataGrid/FlatTreeDataGridSample/readme.md
index ed6c2d7..b79beaa 100644
--- a/TreeDataGrid/FlatTreeDataGridSample/readme.md
+++ b/TreeDataGrid/FlatTreeDataGridSample/readme.md
@@ -10,6 +10,7 @@ This `FlatTreeDataGridSource` sets up a grid which displays a list of countries
 
 ### Column Configuration
 - **Multiple Column Types**: The sample shows how to define different column types:
+  - A row header column for row numbers. Together with the `FrozenColumnCount` property, this keeps the row numbers visible during horizontal scrolling.
   - Read/write text columns with the `Country` name column
   - Template columns with custom cell and edit templates for the `Region` column
   - Read-only text columns for data like `Population` and `Area`
@@ -26,6 +27,7 @@ This `FlatTreeDataGridSource` sets up a grid which displays a list of countries
 - **Column Header Styling**: Custom styling for specific column headers (last column appears in bold)
 - **Cell Styling**: Custom styling for specific cells (last column cells appear in bold)
 - **Custom Templates**: Both display and edit templates for the Region column, including a ComboBox for selection
+- **Frozen Columns**: Keeping certain columns fixed during horizontal scrolling by setting `TreeDataGrid.FrozenColumnCount`
 
 ### Data Binding
 - Proper MVVM implementation showing how to bind a collection of domain objects (Countries) to the TreeDataGrid