I answered you in the formal support ticket that you have opened on that matter. I am also posting the answer here for other to see, but if you have any further concerns, let us continue posting in the formal support thread.
You do not need to switch to advanced data-binding. Filtering with a LinqDataSource and RadGrid works out-of-the-box, as you can see in this online demo
The problem should be caused by something else in the grid setup. As you probably know, this exception is thrown when a postback/callback is fired by an event which is not expected by the Runtime. My first suggestion is that this is related to the Filter command button.
In order to confirm if this is the problem, you can check if the error will go away if you:
-Set a custom command name to the button
-In item command, on this command name, access the grid filtering items (this can be done by using the GetItems(itemType)
method) and fire filtering commands for the ones you want.
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