RadContextMenu have IsOpen property which you can set from code in order to open it.
Here is how:
var contextmenu = RadContextMenu.GetContextMenu(
Let us know if you need more information.
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? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items