Yes, there are a couple of ways to troubleshoot this. You can check if a provider has registered by the using the ServiceProvider.ResolvePersistenceProvider method. You need to pass the type of the provider you wish to resolve as generic parameter and the type that it has been registered to :
If you are using the IsolatedStorageProvider, you can also check the persistence storage and how many items it contains. You can do this using the PersistenceManager.GetStorage() static method and check its Count property.
One thing that I can think off the top of my head is to check whether you have set the PersistenceManager.StorageId property on the control itself, so that it is registered in the storage.
If you have already checked the above, another issue might be that the control has been unregistered. We currently have such issue, when the controls are unregistered from the store when their Unload event is raised (when they are removed from the visual tree). If this is the case, then we have already resolved this and will be available for Q3 2011.
Please let me know if you have questions on this matter.
the Telerik team
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