Hello Jordi Borras,
Thank you for writing.
You are not using the safe casting operators of C#. You need to use the "is" and "as" operators in order to safely cast from one type to another. Also, another issue with the code you posted is that you are calling GetType() on a variable named "c" and then casting a different variable named "control". Please review your code and apply the necessary modifications.
Write again if you need further assistance.
All the best,
the Telerik team
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