Hello Laura,
Thank you for writing.
I think that the RadDropDownList.
SelectedIndexChanging event is the appropriate one for your specific case. It is possible to determine which is the new item's index and perform the necessary action. Afterwards, cancel the event in order to keep the selection unchanged. Here is a sample code snippet:
I hope this information helps. Should you have further questions, I would be glad to help.
Regards,
Desislava
Telerik
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