I didn't find a solution to set the multi selection for rows in the treegrid by code.
I have added a little sample with my problem.
If i click the button some selections should be set in the treegrid (e.g. index 0,2,4).
Some samples shows the the selection can be shown by "....addClass("e-selectionbackground e-active")", but if i add some additional selections (Ctrl+Click), in the rowSelected event the args.model.selectedItems would not return the selections that are only set with "....addClass("e-selectionbackground e-active")".
Is there any possibility to make a multi row select in the treegrid by code where the selectedItems(or an other property) holds the correct selected items?