I'm getting this same problem but the form view state won't work. When I let the detail view return to it's post update state and then give them a link to get back to the full list it does not cause this error. Thanks so much mokeefe, I've always relied on the kindness of strangers. My work around before has been to set the "Enable View State" property to false for the formview.
(Kind of defeates the purpose of having two separaet templates, though.) Sure, it seems that disabling the viewstate on the formview "fixes" this problem. It seems like disabling the viewstate is only fixing the symptoms and not the cause. Details View Updated Event Args) _ Handles dv Beitr Arten.
I dont know if this would help anyone, but after grappling with this issue for a couple of hours here's how I solved the problem. The first tab Panel of the main tab container control a multiview control.
I then simplified the form and removed all unnecessary controls. Details View Inserted Event Args) _ Handles dv Beitr Arten.
I then started manually turning on the viewstate for the Form View and all of it's parent controls.
Anyways I tried setting the Default Mode of my formview to "Edit" and the viewstate loading issue has disappeared.
Note also that I do *NOT* have the exact same controls on my Item Template and my Edit Template and it still works.However today I had to create a page that contained a Multi View within the templates of the formview (yes its a giant mess).Anyways the viewstate of controls on some of the views would not persist their data so this was a serious issue.I believe that viewstate is actually loaded from the parent control and if the viewstate for the parent control is false, then the viewstate for all the child controls will be discarded because the parent controls viewstate is disabled. It could also come down to the way controls with ITemplate properties carry and populate viewstate. Since, the Update Panel uses an ITemplate to render it's children, then the update panel may not populate the child control until databinding, or final rendering. Right now the form does not have an Insert Template but I will be adding it shortly.