The provided information is not enough for us to determine the problem.
From the message it is clear that your code gets executed - the info you see is the result of the RadWindow object being evaluated in the context of a string (because this is the result of its toString()
method being called).
One possibility is that you have constructed your statement incorrectly and you have a + sign in it that causes the RadWindow to be evaluated as a string.
We will be able to provide you with more information if you open a support ticket with your project, or at least post your client-side RadWindow invocation code here.
the Telerik team
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