Angular Tree Grid Row Selection

With row selection in Ignite UI for Angular, there is row selector column that precedes all other columns within the row. When a user clicks on the row selector, the row will either become selected or deselected, enabling the user to select multiple rows of data.

Angular Row Selection Example

The sample below demonstrates the four types of Tree Grid's row selection behavior. Use the buttons below to enable each of the available selection modes. A brief description will be provided on each button interaction through a snackbar message box. Use the switch button to hide or show the row selector checkbox.

Setup

In order to setup row selection in the igx-tree-grid, you just need to set the rowSelection property. This property accepts GridSelectionMode enumeration. GridSelectionMode exposes the following four modes: none, single, multiple and multipleCascade. Below we will take a look at each of them in more detail.

None Selection

In the igx-tree-grid by default row selection is disabled, otherwise ([rowSelection]="'none'"). So you can not select or deselect a row through interaction with the Tree Grid UI, the only way to complete these actions is to use the provided API methods.

Single Selection

Single row selection can now be easily set up, the only thing you need to do, is to set [rowSelection] = '"single"' property. This gives you the opportunity to select only one row within a grid. You can select a row by clicking on a cell or pressing the space key when you focus on a cell of the row, and of course you can select a row by clicking on the row selector field. When row is selected or deselected rowSelectionChanging event is emitted.

<!-- selectionExample.component.html -->

<igx-tree-grid [data]="data" primaryKey="ID" foreignKey="ParentID" [autoGenerate]="true"
            [rowSelection]="'single'" [allowFiltering]="true" (rowSelectionChanging)="handleRowSelection($event)">
</igx-tree-grid>

/* selectionExample.component.ts */

public handleRowSelection(event) {
    if (args.added.length && args.added[0] === 3) {
        args.cancel = true;
    }
}

Multiple Selection

To enable multiple row selection in the igx-tree-grid just set the rowSelection property to multiple. This will enable a row selector field on each row and in the Tree Grid header. The row selector allows users to select multiple rows, with the selection persisting through scrolling, paging, and data operations, such as sorting and filtering. The row also can be selected by clicking on a cell or by pressing the space key when a cell is focused. If you have selected one row and click on another while holding the shift key, this will select the whole range of rows. In this selection mode, when you click on a single row, the previous selected rows will be deselected. If you click while holding the ctrl key, the row will be toggled and the previous selection will be preserved.

<!-- selectionExample.component.html -->

<igx-tree-grid [data]="data" primaryKey="ID" foreignKey="ParentID" [rowSelection]="'multiple'"
        [allowFiltering]="true" (rowSelectionChanging)="handleRowSelection($event)" >
</igx-tree-grid>

Cascade Selection

To enable cascade row selection in the igx-tree-grid just set the rowSelection property to multipleCascade. This will enable a row selector field on each row and in the Tree Grid header. The row selector allows users to select multiple rows which would select all children in the tree below. The selection persists through scrolling, paging, and data operations, such as sorting and filtering. The row can also be selected by clicking on a cell or by pressing the space key when a cell is focused. If you have selected one row and click on another while holding the shift key, the selection of a parent record will select all of its children even if they are not in the selected range. In this selection mode, when you click on a single row, the previously selected rows will be deselected. If you click while holding the ctrl key, the row and its children will be toggled and the previous selection will be preserved.

<!-- selectionExample.component.html -->

<igx-tree-grid [data]="data" primaryKey="ID" foreignKey="ParentID" [autoGenerate]="true"
        [rowSelection]="'multipleCascade'" [allowFiltering]="true" (rowSelectionChanging)="handleRowSelection($event)">
</igx-tree-grid>

In this mode a parent's selection state entirely depends on the selection state of its children. When a parent has some selected and some deselected children, its checkbox is in an indeterminate state.

<!-- selectionExample.component.ts -->

 public handleRowSelection(event: IRowSelectionEventArgs) {
    // use event.newSelection to retrieve primary key/row data of latest selected row
    this.selectedRowsCount = event.newSelection.length;
    this.selectedRowIndex = event.newSelection[0];
 }

Notes

Row selection will trigger rowSelectionChanging event. This event gives you information about the new selection, old selection, the rows that have been added and removed from the old selection. Also the event is cancellable, so this allows you to prevent selection.
When row selection is enabled row selectors are displayed, but if you don't want to show them, you can set [hideRowSelectors] = true.
When you switch between row selection modes at runtime, this will clear the previous row selection state.

API usage

Select rows programmatically

The code snippet below can be used to select one or multiple rows simultaneously (via primaryKey); Additionally, the second parameter of this method is a boolean property through which you may choose whether the previous row selection will be cleared or not. The previous selection is preserved by default.

<!-- selectionExample.component.html -->

<igx-tree-grid ... [primaryKey]="'ID'">
...
</igx-tree-grid>
...
<button (click)="this.treeGrid.selectRows([1,2,5], true)">Select 1,2 and 5</button> // select rows and clear previous selection state

This will add the rows which correspond to the data entries with IDs 1, 2 and 5 to the Tree Grid selection.

Deselect rows

If you need to deselect rows programmatically, you can use the deselectRows(rowIds: []) method.

<!-- selectionExample.component.html -->

<igx-tree-grid ... [primaryKey]="'ID'">
...
</igx-tree-grid>
...
<button (click)="this.treeGrid.deselectRows([1,2,5])">Deselect 1,2 and 5</button>

Row selection event

When there is some change in the row selection rowSelectionChanging event is emitted. rowSelectionChanging exposes the following arguments:

oldSelection - array of row's data that contains the previous state of the row selection.
newSelection - array of row's data that match the new state of the row selection.
added - array of row's data that are currently added to the selection.
removed - array of row's data that are currently removed according old selection state.
event - the original event that triggered row selection change.
cancel - allows you the prevent the row selection change.

Row selection event in remote data scenarios

In remote data scenarios, when the grid has a primaryKey set, rowSelectionChanging.oldSelection event argument will not contain the full row data object for the rows that are currently out of the data view. In this case, rowSelectionChanging.oldSelection object will contain only one property, which is the primaryKey field. For the rest of the rows, currently in the data view, rowSelectionChanging.oldSelection will contain the whole row data.

<!-- selectionExample.component.html -->

<igx-tree-grid (rowSelectionChanging)="handleRowSelectionChange($event)">
...
</igx-tree-grid>

/* selectionExample.component.ts */

public handleRowSelectionChange(args) {
    args.cancel = true; // this will cancel the row selection
}

Select all rows

Another useful API method that igx-tree-grid provides is selectAll(onlyFilteredData). By default this method will select all data rows, but if filtering is applied, it will select only the rows that match the filter criteria. But if you call the method with false parameter, selectAll(false) will always select all data in the grid, even if filtering is applied.

Note

Keep in mind that selectAll() will not select the rows that are deleted.

Deselect all rows

igx-tree-grid provides deselectAll(onlyFilteredData) method, which by default will deselect all data rows, but if filtering is applied will deselect only the rows that match the filter criteria. But if you call the method with false parameter, deselectAll(false) will always clear all row selection state even if filtering is applied.

How to get selected rows

If you need to see which rows are currently selected, you can get their row IDs with the selectedRows getter.


public getSelectedRows() {
    const currentSelection = this.treeGrid.selectedRows; // return array of row IDs
}

Additionally, assigning row IDs to selectedRows will allow you to change the grid's selection state.

public mySelectedRows = ['Johnathan Winchester', 'Ana Sanders']; // an array of row IDs

<igx-tree-grid primaryKey="ID" rowSelection="multiple" [autoGenerate]="false" [selectedRows]="mySelectedRows" [data]="data">
    <igx-column [field]="'Name'"></igx-column>
    <igx-column [field]="'Title'"></igx-column>
</igx-tree-grid>

Row selector templates

You can template header and row selectors in the Tree Grid and also access their contexts which provide useful functionality for different scenarios.

By default, the Tree Grid handles all row selection interactions on the row selector's parent container or on the row itself, leaving just the state visualization for the template. Overriding the base functionality should generally be done using the rowSelectionChanging event. In case you implement a custom template with a click handler which overrides the base functionality, you should stop the event's propagation to preserve the correct row state.

Row template

To create a custom row selector template, within the igx-tree-grid, declare an <ng-template> with igxRowSelector directive. From the template you can access the implicitly provided context variable, with properties that give you information about the row's state.

The selected property shows whether the current row is selected or not while the index property can be used to access the row index.

<ng-template igxRowSelector let-rowContext>
    {{ rowContext.index }}
    <igx-checkbox
        [checked]="rowContext.selected"
        [readonly]="true"
    ></igx-checkbox>
</ng-template>

The rowID property can be used to get a reference of an igx-tree-grid row. This is useful when you implement a click handler on the row selector element.

<ng-template igxRowSelector let-rowContext>
    <igx-checkbox (click)="onSelectorClick($event, rowContext.key)"></igx-checkbox>
</ng-template>

In the above example we are using an igx-checkbox and we bind rowContext.selected to its checked property. See this in action in our Row Numbering Demo.

Header template

To create a custom header selector template, within the Tree Grid, declare an <ng-template> with igxHeadSelector directive. From the template you can access the implicitly provided context variable, with properties that give you information about the header's state.

The selectedCount property shows you how many rows are currently selected while totalCount shows you how many rows there are in the Tree Grid in total.

<ng-template igxHeadSelector let-headContext>
    {{ headContext.selectedCount }} / {{ headContext.totalCount  }}
</ng-template>

The selectedCount and totalCount properties can be used to determine if the head selector should be checked or indeterminate (partially selected).

<igx-tree-grid [data]="tGridData" primaryKey="ProductID" childDataKey="Products">
    <!-- ... -->
    <ng-template igxHeadSelector let-headContext>
        <igx-checkbox
            [checked]="headContext.selectedCount > 0 && headContext.selectedCount === headContext.totalCount"
            [indeterminate]="headContext.selectedCount > 0 && headContext.selectedCount !== headContext.totalCount">
        </igx-checkbox>
    </ng-template>
</igx-tree-grid>

Row Numbering Demo

This demo shows the usage of custom header and row selectors. The latter uses rowContext.index to display row numbers and an igx-checkbox bound to rowContext.selected.

Conditional Selection Demo

This demo prevents some rows from being selected using the rowSelectionChanging event and a custom template with disabled checkbox for non-selectable rows.

API References

Additional Resources

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