TreeDataGrid v12 Breaking Changes

TreeDataGrid v12 introduces a new XAML-first workflow and a new fluent source API. The most important changes are:

Generic column types were replaced by non-generic TreeDataGrid*Column types.
ItemsSource plus declarative columns is now a first-class setup path.
Code-based sources now use fluent builders such as WithTextColumn and WithHierarchicalExpanderColumn.
Column option classes moved to top-level *CreateOptions types and CanUserResizeColumn became CanUserResize.
Text-column text search now defaults to true.
SelectionMode and control-level SelectionChanged were added to TreeDataGrid.
Hierarchical row events now use TreeDataGridRowModelEventArgs.
Template-column text search now uses TextSearchBinding.
FlatTreeDataGridSource<TModel> and HierarchicalTreeDataGridSource<TModel> are sealed.

Typical Migrations

Text columns

source.WithTextColumn("Name", x => x.Name, o => o.Width = GridLength.Star);

Check box columns

source.WithCheckBoxColumn("Active", x => x.IsActive);

Template columns

source.WithTemplateColumnFromResourceKeys("Status", "StatusCell", "StatusEditCell", o =>
{
    o.TextSearchBinding = new Avalonia.Data.Binding("Name");
});

Hierarchical expander columns

source.WithHierarchicalExpanderTextColumn(x => x.Name, x => x.Children, o =>
{
    o.HasChildren = x => x.HasChildren;
    o.IsExpanded = x => x.IsExpanded;
});

XAML Migration

Older code typically bound only Source. In v12-style code you can declare columns directly on the control:

<TreeDataGrid ItemsSource="{Binding People}">
  <TreeDataGridTextColumn Header="Name"
                          Binding="{Binding Name}"/>
</TreeDataGrid>