ASP.NET: RadioButtonList in Repeater in UpdatePanel – Stopping Full Postback

I came across an issue today where a RadioButtonList (with AutoPostback==true) inside a Repeater inside an UpdatePanel was causing a full page postback instead of a partial postback. Apparently this is due to a change in how ClientIDs are generated in .Net 4+.

The workaround is to set ClientIDMode=”AutoID” on the RadioButtonLists.