One way is to make a public function on your UserControls that handles the rest logic for you:
public void Reset()
{
}
Then you can hook into the TabControl's Deselected event and call the reset function:
private void tabControl1_Deselected ( object sender, TabControlEventArgs e )
{
switch ( e.TabPageIndex )
{
case 0:
this.userControl1.Reset ();
break;
case 1:
this.userControl2.Reset ();
break;
}
}