Why would my child controls be uninitialized at the time of event attachment?

Answer 1

The reason this works:

protected void Page_Load(object sender, EventArgs e)
{
    RecordSelector1.DropDownSelectedIndexChanged 
        += new EventHandler(RecordSelector1_DropDownSelectedIndexChanged);
}

and this does not:

<cc1:RecordSelector ID="RecordSelector1" runat="server"
OnDropDownSelectedIndexChanged="RecordSelector1_DropDownSelectedIndexChanged" />

is because the first one adds the handler after the control has been initialized (via the page's Init). The second example gets parsed much earlier and as such the page is attempting to add the handler before the control has initialized.

Due to the nature of the page's life cycle I think you may have to live with adding the event handler in the code-behind. There will be no way to add the handler before the control is initialized because that control will always be null prior to initialization.