Timer causes dropdownlists to disappear permanently after a modal popup

On a fairly complex page, we're getting some unusual behavior with dropdownlists in IE6. To layout the basic structure, there are 2 update panels on the page each with a GridView presenting a master-detail开发者_如何学Gos layout. In addition to the grid, each panel houses some DropDownLists for filtering the data in the respective GridView.

Now what's happening is that a button on the bottom grid will cause a modal popup form to display, where some details about the row item can be modified. As per the ASP.NET AJAX JavaScript, the DropDowns disable during the postback, and re-enable after it closes.

The bottom grid also has a timer attached to it that periodically updates it to keep the view of the data fresh. When this timer ticks after the modal popup is closed, the drop down lists mysteriously vanish, except for the ones in that update panel which apparently get rendered again.

Oddly enough, if the timer ticks while the popup is up, the drop downs enable early and show through the modal (oh IE6...) but don't vanish later on.

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Been a while since I posted this, but the problem occasionally resurfaces and I think I finally found an answer to it.

The AJAX Toolkit's modal popup javascript disables all DropDownLists on the page because they show through to the highest Z-level in IE6. But if something causes a postback while the modal is showing (like a badly managed timer) then the invisible state gets recorded into the viewstate for the DDLs.

One easy way around it is to just put the offending DDLs in an update panel, so they properly get refreshed on updates and don't get stuck. The more complex way is to ensure nothing causes extraneous postbacks while the modal is showing. The best way would probably be to ditch Webforms and all the baggage with it, but that's pretty much not going to happen.