How to prevent full page postback on selectedindexchange for dropdownlist

Answer 1

You'd need to specify ChildrenAsTriggers="true" in your UpdatePanel tag. The error you're getting is because your dropdown doesn't physically exist in the markup, which is what a Trigger line expects to find during compliation/runtime - instead, you are adding it dynamically as a control in your RowCreated function. It might be possible to, in that same function, add a trigger to the UpdatePanel dynamically, if you wanted to try that, instead.