Hello Rob,
Technically it is possible to virtualize RadMenuItems so they will load faster. But from UX point I'm not sure how usable it will be to have 100 subItems.
I've attached sample project with modified RadMenuItem templates that includes custom scroll and item virtualization. There are 5 top level items each with 100 sub items and each of them with 100 sub items (3 level deep menu). There is also RadContextMenu which is also virtualized. (this is Silverlight 4 project with 2010.Q2.SP1 trail assemblies).
I hope that this example will be helpful.
Let us know if you need more information.
Regards,
Hristo
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