Probably this is an ignorance of Async postbacks, so let me lob a softball out there.
I have three cascading dropdowns in an updatepanel, using these you can pick your Store->Department->Product. A fourth DDL sits outside the updatepanel, and using this you pick your competitor. Different stores match with different competitors. A gridview (also outside) then displays the join of Store->Department->Product->Competitor Price.
This works fine when you first load and if you switch to a different store that has the same competitor. But if you change the updatepanel DDLs to a store that does not share the chosen competitor and click "Display" (causing a PostBack), I get an "Invalid Postback or callback argument." If I remove the Competitor DDL and hardcode the gridview's competitor, the error goes away and I can navigate with abandon.
Why won't that fourth DDL repopulate on postback? How do I fix this problem?
See Question&Answers more detail:os