selectedIndex is lost during postbacks - ASP.NET

Question

I have a list box control:

The code behind resembles:

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Answer 1

What's the output of the foo() function call?

Populating manually the list box you can set indexes to whatever you want (all 0 for example) - so the same thing can happen setting a given dataSource under certain circumstances (one that specifies indexes I suppose). If all the item indexes are 0 the result is that the SelectedIndexChanged event is not raised (index does not change!) and everything is messed up: on post-back selection will go back to the first item in the list.

This would explain it - I cannot think of anything else - it is working fine for me on .NET 2.0 I am using an ArrayList with strings to populate the listBox.

The only way I can reproduce your issue is setting all indexes to 0.

I'd say add a watch to the ListBox and check the indexes at runtime to make sure they're not all zeroes.