If Not trRef.Attributes.CssStyle.Value.Contains("display:none;") 'row is visible End If
But the CssStyle property is empty (as I gather the controls have been recreated from the viewstate). I thought I might be able to use Request.Form(control.UniqueID) (as per this post) but it seems this will only retrieve the value of a control, and nothing else?
How can I determine whether these rows are visible on post back?
Styles are not posted to the server, just form values.
You'll need to generate a different mechanism. For instance a hidden field containing visible rows (or hidden ones) indexes separated by comman and you'd process this hidden field on the server.