Tree grid selection

projects/igniteui-angular/src/lib/core/selection.ts

@@ -208,7 +208,7 @@ export class IgxSelectionAPIService {
      * @returns If all items are selected.
      */
     public are_all_selected(componentID: string, dataCount: number): boolean {
-        return this.size(componentID) === dataCount;
+        return dataCount > 0 && dataCount === this.size(componentID);
     }
 
     /**

projects/igniteui-angular/src/lib/grids/tree-grid/tree-grid-api.service.ts

@@ -123,4 +123,17 @@ export class IgxTreeGridAPIService extends GridBaseAPIService<IgxTreeGridCompone
     public should_apply_number_style(column: IgxColumnComponent): boolean {
         return column.dataType === DataType.Number && column.visibleIndex !== 0;
     }
+
+    public get_selected_children(id: string, record: ITreeGridRecord, selectedRowIDs: any[]) {
+        const grid = this.get(id);
+        if (!record.children || record.children.length === 0) {
+            return;
+        }
+        for (const child of record.children) {
+            if (grid.selection.is_item_selected(id, child.rowID)) {
+                selectedRowIDs.push(child.rowID);
+            }
+            this.get_selected_children(id, child, selectedRowIDs);
+        }
+    }
 }

projects/igniteui-angular/src/lib/grids/tree-grid/tree-grid-selection.spec.ts

@@ -84,6 +84,25 @@ describe('IgxTreeGrid - Selection', () => {
             TreeGridFunctions.verifyHeaderCheckboxSelection(fix, false);
         });
 
+        it('when all items are selected and then some of the selected rows are deleted, still all the items should be selected', () => {
+            treeGrid.selectAllRows();
+            fix.detectChanges();
+            TreeGridFunctions.verifyHeaderCheckboxSelection(fix, true);
+
+            treeGrid.deleteRowById(treeGrid.selectedRows()[0]);
+            fix.detectChanges();
+            TreeGridFunctions.verifyHeaderCheckboxSelection(fix, true);
+
+            treeGrid.deleteRowById(treeGrid.selectedRows()[0]);
+            fix.detectChanges();
+            TreeGridFunctions.verifyHeaderCheckboxSelection(fix, true);
+
+            treeGrid.deleteRowById(treeGrid.selectedRows()[0]);
+            fix.detectChanges();
+             // When deleting the last selected row, header checkbox will be unchecked.
+            TreeGridFunctions.verifyHeaderCheckboxSelection(fix, false);
+        });
+
         it('should be able to select row of any level', () => {
             treeGrid.selectRows([treeGrid.getRowByIndex(0).rowID], true);
             fix.detectChanges();

projects/igniteui-angular/src/lib/grids/tree-grid/tree-grid.component.ts

@@ -429,6 +429,13 @@ export class IgxTreeGridComponent extends IgxGridBaseComponent {
             const childData = record.parent ? record.parent.data[this.childDataKey] : this.data;
             index = this.primaryKey ? childData.map(c => c[this.primaryKey]).indexOf(rowID) :
                 childData.indexOf(rowID);
+
+            const selectedChildren = [];
+            this._gridAPI.get_selected_children(this.id, record, selectedChildren);
+                if (selectedChildren.length > 0) {
+                this.deselectRows(selectedChildren);
+            }
+
             if (this.transactions.enabled) {
                 this.transactions.add({
                     id: rowID,