Row Selection Guide

Row selection is the default selection mode for both flat and hierarchical sources.

Default and Multi-Select

By default:

row selection model is created lazily
SingleSelect = true

Enable multi-select:

Source.RowSelection!.SingleSelect = false;

Selecting by IndexPath

Source.RowSelection!.SelectedIndex = new IndexPath(0, 1);

For flat sources, implicit int conversion is available:

Source.RowSelection!.SelectedIndex = 3;

Read Selected Items

var selection = Source.RowSelection!;
var first = selection.SelectedItem;
var all = selection.SelectedItems;
var indexes = selection.SelectedIndexes;

Programmatic Operations

Available operations (through ITreeSelectionModel):

Select(IndexPath)
Deselect(IndexPath)
Clear()
IsSelected(IndexPath)

Batch updates for advanced scenarios:

selection.BeginBatchUpdate();
try
{
    selection.Select(new IndexPath(0));
    selection.Select(new IndexPath(1));
}
finally
{
    selection.EndBatchUpdate();
}

Events

Typed event:

Source.RowSelection!.SelectionChanged += (_, e) =>
{
    // e.SelectedIndexes, e.DeselectedIndexes
    // e.SelectedItems, e.DeselectedItems
};

Base model events (advanced):

IndexesChanged
SourceReset

SourceReset is important when the underlying collection raises Reset.

UI Integration

From TreeDataGrid control:

RowSelection property returns active row selection model when in row mode
keyboard and pointer interactions route through selection interaction contract

Common Pitfalls

assigning a custom selection model whose Source differs from source Items
persisting visible row indexes instead of IndexPath
forgetting to disable SingleSelect for Ctrl/Shift style multi-selection workflows

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.