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Cell Selection Guide

Use cell selection when interactions should target individual cells rather than whole rows.

Enable Cell Selection

using Avalonia.Controls.Selection;

Source.Selection = new TreeDataGridCellSelectionModel<Person>(Source)
{
    SingleSelect = false,
};

When active, source exposes:

  • Source.CellSelection

Single Cell Selection

Source.CellSelection!.SelectedIndex = new CellIndex(
    columnIndex: 2,
    rowIndex: new IndexPath(0, 1));

Read selection:

var current = Source.CellSelection!.SelectedIndex;
var all = Source.CellSelection.SelectedIndexes;

Range Selection

Source.CellSelection!.SetSelectedRange(
    start: new CellIndex(1, new IndexPath(0)),
    columnCount: 3,
    rowCount: 5);

This clears existing selection and selects a rectangular range.

Selection Events

Source.CellSelection!.SelectionChanged += (_, e) =>
{
    // event fired when selected cells change
};

For control-level visuals, TreeDataGrid routes selection interaction updates to realized rows/cells.

Checking Membership

var isSelected = Source.CellSelection!.IsSelected(new CellIndex(0, new IndexPath(2)));

Keyboard and Pointer Behavior

Cell model handles:

  • arrow navigation across row/column axis
  • Shift range extension
  • pointer press/release selection behavior

Behavior is implemented through ITreeDataGridSelectionInteraction.

Common Pitfalls

  • using cell selection but reading RowSelection
  • assigning CellIndex with model index that is not currently represented in source
  • expecting additive range API behavior: SetSelectedRange replaces 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.

API Coverage Checklist