Thank you for the code example.
Regarding your question about Web Farm environment. Using the aspnet cache provider means that the page output will be stored in the memory. This has nothing to do with the cache dependency. In a load balanced environment, if you want changes made on one server to take effect to the others, you should set the cacheDependency mode to InDatabase in the web.config:
| <caching defaultProvider="memoryCache">
| <cacheDependency mode="InDatabase"/>
As for the example, the user control throws an exception. Actually, the ScriptManager is on the page, but it is loaded just after the control, which is the reason for the exception. We fixed the problem for the upcoming release, however it will be complicated to provided a workaround with the current release.
Alternatively, it works fine with the RadAjaxPanel. However, there is another problem there, the work around for which is described in this forum
We apologize for the omissions. Your telerik points were updated for pointing us the problem with UpdatePanel.
For the last issue, with the common user control, which inherits from CacheSubstitutionUserControl, unfortunately we cannot reproduce and understand it. Seems this error is not thrown by our application. We have no idea how it can be related to this scenario. Can you give us more details? Or, is it possible for you to provide a code example again?
the Telerik team