You can set the RadContextMenu.IsOpen property to true for showing the context menu like the following:
sender, System.Windows.Input.MouseEventArgs e)
.contextMenu.PlacementTarget = sender
But I can't recommend the behavior with using MouseEnter and MouseLeave events for opening context menu, because when the user is trying to use the context menu then the MouseLeave will occur on a pushpin. In this case the menu will be closed. You should implement a logic with using timeouts to close context menu after the MouseLeave occurs but when the context menu is not focused. Also you should handle the MouseLeave event on the context menu to close it when the user didn't click any item of context menu. The implementation of this code is out of the support scope of RadMap control. You should implement it by yourself.
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