Dropdownlist Remove one item in C#.net.

Dropdownlist1.Items.Remove(Dropdownlist1.Text);
// rimuove l'elemento selezionato al momento...

DropDownList1.Items.Remove("Item");

int i=Dropdownlist1.Items.count;
for(int j=0;j<i;j++)>
{
    if(Dropdownlist1.Items[j].selected==true)
    {
        Dropdownlist1.Items.Remove(Dropdownlist1.Items[i].toString();
        i--;
    }
}

event: protected void drop_downList1_SelectedIndexChanged(object sender, EventArgs e)
{

}

protected void drop_downList1_SelectedIndexChanged(object sender, EventArgs e)
{

  string selectedSub = ddlRepetsub1.SelectedItem.Text;

  drop_downList2.Items.FindByText(selectedSub).Enabled = false;

}

protected void drop_downList1_SelectedIndexChanged(object sender, EventArgs e)
{
   string selectedSub = ddlRepetsub1.SelectedItem.Text; 

   drop_downList2.Items.Remove(selectedSub);

}