Try this,
int yr = 2012;
string[] monthNames = { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };
for (int cnt = yr - 5; cnt < yr; cnt++)
{
for (int mth = 0; mth <= 11; mth++)
{
ddl_Years.Items.Add(monthNames[mth] + "-" + cnt.ToString());
}
}
ddl_Years.Items.Insert(0, new ListItem("--Please Select--", "0"));