The RadDockZone does not provide a property which can be set to lock the zone if a predetermined limit of docks have already been docked in it. If you want to avoid users dropping docks in a zone in which there already are a predetermined number of docks I could suggest you use the OnClientDragStart
and the OnClientDragEnd
client events to do the check. At the OnClientDragStart you can save the dock's current parent zone and at OnClientDragEnd check the number of docks of the zone in which the dock is just dropped and if it is greater than the predetermined limit for the corresponding zone return the just dropped dock to its previous location.
Let us know if you need further assistance.
the Telerik team