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>No. I have no experience with ClientID at all. How is it different, with regards to this problem of not finding the control?
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>Somehow this thread got split into two sections. I suppose that happens.
>

ASP.NET generates two different ID's for controls - the UniqueID and the ClientID. ClientID is meant for client-side access so it's more commonly used when Javascript code in the page needs to access the controls. UniqueID is meant for server-side access (so I'm surprised that's not working).

ASPxRoundPanel1.FindControl("HiddenField1").ClientID