XAML Samples Walkthrough

This article explains the TreeDataGrid XAML patterns used in samples/TreeDataGridDemo.

Application-Level Theme Include

App.axaml configures Fluent theme and TreeDataGrid styles:

<Application.Styles>
  <FluentTheme/>
  <StyleInclude Source="avares://Avalonia.Controls.TreeDataGrid/Themes/Fluent.axaml"/>
</Application.Styles>

The sample also includes commented resource overrides for TreeDataGrid-specific brush keys.

Window-Level XAML and Compiled Bindings

MainWindow.axaml enables typed compiled bindings:

<Window x:CompileBindings="True"
        x:DataType="vm:MainWindowViewModel">

This keeps XAML bindings strongly typed and easier to refactor.

Per-Grid Template Resources

Sample tabs define TreeDataGrid.Resources with keyed templates:

<TreeDataGrid.Resources>
  <DataTemplate x:Key="RegionCell" DataType="m:Country">
    <TextBlock Text="{Binding Region}"/>
  </DataTemplate>
  <DataTemplate x:Key="RegionEditCell" DataType="m:Country">
    <ComboBox ItemsSource="{x:Static m:Countries.Regions}"
              SelectedItem="{Binding Region}"/>
  </DataTemplate>
</TreeDataGrid.Resources>

View models use the same keys through TemplateColumn<TModel> constructors.

Per-Grid Styles and Selectors

The sample applies style selectors in TreeDataGrid.Styles to:

stripe rows
make a specific cell column bold
style a specific header column

This is useful for local visual behavior without replacing global control themes.

XAML Interaction Wiring

The sample declares interaction options in markup:

<TreeDataGrid AutoDragDropRows="True"
              RowDragStarted="DragDrop_RowDragStarted"
              RowDragOver="DragDrop_RowDragOver"/>

Resource Keys from Model Layer

Sample view models pass template key names into columns:

new TemplateColumn<Country>("Region", "RegionCell", "RegionEditCell")

This key is resolved at runtime using the realized template-cell control as the resource lookup anchor (within the grid's logical/resource scope).

Troubleshooting

DataTemplate key exists but still not found Cause: key is not visible in the lookup scope of the grid/cell anchor. Fix: place template in TreeDataGrid.Resources, parent logical resources, or application resources.
Template renders but data is empty Cause: template DataType or binding path does not match model shape. Fix: verify model type and binding members against the row model used by the column.
Editing starts and throws template-key exception Cause: editing template key was provided in model code but corresponding DataTemplate key is missing in resources. Fix: add the keyed editing template or use the non-editing constructor path.