Hi,
short answer is that you should be able to bind an event handler to change index event of drop-down list and set current page of the pager in code.
The code should like this:
// Event handler registration
ddlYear.SelectedIndexChanged += SelectedYearChanged;
// Event handler
protected void SelectedYearChanged(object sender, EventArgs eventArgs)
{
pager.CurrentPage = 1;
}
However if you already tried this and it does not work, I would suggest to try adjusting update panel settings / content.
Since it looks like what you need is short tip, I did not try to reproduce your situation, so if you need further assistance, please let us know and provide us further information.