You can use the Up / Down / Left / Right arrows to navigate in RadTreeListView. You can test this in our online demo
As for your second question - you can subscribe to the CellValidating event and define its handler as below:
sender, GridViewCellValidatingEventArgs e)
&& e.NewValue ==
Club).StadiumCapacity = 0;
Hope this helps.
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items