public static void InsertTabPage(this TabControl tc, TabPage tabpage, int index)
{
if (index < 0 || index > tc.TabCount)
{
throw new ArgumentException("Index out of Range.");
}
tc.AddTabPage(tabpage);
if (index < tc.TabCount - 1)
{
do
{
tc.SwapTabPages(tabpage, (tc.TabPages[tc.TabPages.IndexOf(tabpage) - 1]));
}while (tc.TabPages.IndexOf(tabpage) != index);
}
tc.SelectedTab = tabpage;
}