Selection in the .NET MAUI TreeDataGrid

The Telerik UI for .NET MAUI TreeDataGrid exposes a single and multiple selection feature which enables users to select a cell or a row by clicking (tapping) on it.

Users can cancel the selection by clicking the cell or the row again.

To implement the selection feature of the TreeDataGrid, use any of the available properties, methods, and events supported by the DataGrid and depending on your scenario.

Properties

To modify the selection modes of the DataGrid, use some of its most common properties such as SelectionUnit and SelectedItems. To set the SelectionMode property, define which Unit can be selected.

SelectionUnit

The SelectionUnit property of type Telerik.Maui.Controls.DataGrid.DataGridSelectionUnit allows you to control which Unit can be selected:

• (Default) Row—The unit that will be selected is a DataGrid row.
• Cell—The unit that will be selected is a cell within a DataGrid row.

To define a cell when using a selection, utilize the DataGridCellInfo class that holds all the information about the cell. To define a row when using a selection, you can use your data object.

The example below shows how to set SelectionUnit in XAML and code-behind:

<telerik:RadTreeDataGrid x:Name="treeDataGrid"
                         SelectionUnit="Cell" />

var treeDataGrid = new RadTreeDataGrid();
treeDataGrid.SelectionUnit = Telerik.Maui.Controls.DataGrid.DataGridSelectionUnit.Cell;

SelectionMode

The SelectionMode property of type Telerik.Maui.Controls.DataGrid.DataGridSelectionMode provides the following modes:

• (Default) Single—Allows you to select a single unit.
• Multiple—Allows you to select multiple units.
• None—Allows no selection.

The example below shows how to set SelectionMode in XAML and code-behind:

<telerik:RadTreeDataGrid x:Name="treeDataGrid"
                         SelectionMode="Multiple" />

var treeDataGrid = new RadTreeDataGrid();
treeDataGrid.SelectionMode = Telerik.Maui.Controls.DataGrid.DataGridSelectionMode.Multiple;

SelectedItems

The TreeDataGrid exposes the SelectedItem and SelectedItems properties which you can use depending on whether you have defined a single or multiple selection mode.

Once you make a selection, you can get or modify the collection with the selected items by using the SelectedItems property of type ObservableCollection<object>. It gets or modifies an ObservableCollection of the currently selected items. Their type depends on the applied SelectionUnit, that is, DataGridCellInfo for a cell and a data item for a row. You can also directly listen to the CollectionChanged event of the SelectedItems.

The SelectedItem property gets or sets the value of the selected item in the DataGrid. The type of the SelectedItem depends on the value of the SelectedUnit.

• Row—SelectedItem is of type DataGridCellInfo.
• Cell—SelectedItem is the same type as the business object.

Events

The TreeDataGrid exposes the SelectionChanged event that is triggered whenever the SelectedItems collection is changed. The SelectionChanged event handler receives the following parameters:

• The sender argument, which is of type object, but can be cast to the RadDataGrid type.
• A DataGridSelectionChangedEventArgs object, which provides the following properties: - RemovedItems—Gets a list of the removed items from the SelectedItems collection. - AddedItems—Gets a list of the added items to the SelectedItems collection.

Methods

The TreeDataGrid exposes additional functionalities for programmatic selection and deselection of items as methods. They also depend on the applied SelectionUnit.

The TreeDataGrid provides the following methods for programmatic selection when the SelectionUnit is Row:

• SelectItem(object item)—Selects the specified data item and adds it to the SelectedItems collection.
• DeselectItem(object item)—Removes the selection for the specified data item and removes it from the SelectedItems collection.

The TreeDataGrid provides the following methods for programmatic selection when the SelectionUnit is Cell:

• SelectCell(DataGridCellInfo item)—Selects the DataGrid cell as defined by the specified cell information.
• DeselectCell(DataGridCellInfo item)—Removes the selection for the DataGrid cell defined by the specified cell information.

The TreeDataGrid provides the following methods for programmatic selection of all items:

• SelectAll()—Selects all the items as defined when the SelectionMode is Multiple.
• DeselectAll()—Clears the current selected items as defined by the SelectionUnit property.

Example

Here are examples for using the exposed methods:

• In the case of row selection, use the SelectItem method:

var firstMarketingItem = ((ObservableCollection<Person>)this.treeDataGrid.ItemsSource).First(p => p.Department == "Marketing");
this.treeDataGrid.SelectItem(firstMarketingItem);

• For a cell selection, use the SelectCell method. It takes as a parameter a DataGridCellInfo object. The DataGridCellInfo object can be easy created by using the needed data item (of type Person in this case) and setting the column corresponding to the cell you need to select.

var firstMarketingCell = ((ObservableCollection<Person>)this.treeDataGrid.ItemsSource).First(p => p.Department == "Marketing");
this.treeDataGrid.SelectCell(new DataGridCellInfo(firstMarketingCell, this.treeDataGrid.Columns[2]));

• Call the SelectAll or DeselectAll method:

this.treeDataGrid.SelectAll();

See Also

• Setting the Telerik UI for .NET MAUI TreeDataGrid Columns
• Filtering .NET MAUI TreeDataGrid Records