Range value setting in C#

string Source = TextBox2.Text;
string oops1,oops2;
int a1, a2;
string[] First = Source.Split('-');
for (int i = 1; i < First.Length; i++)
{
oops1 = First[0];
oops2 = First[1];
a1 = Convert.ToInt32(oops1);
a2 = Convert.ToInt32(oops2);
for (int ii = a1; ii <= a2; ii++)
{
DropDownList1.Items.Add(ii.ToString());
}

}