DropDownList content appears twice - Jquery and asp.net

Is this a bug?
#1

I’m trying to use the Library to enhance the power of a dropdown list though there’s an issue within the drop-down list the content appears twice and I have no clue why.

Using jquery and asp.net:

the jquery function is called once.
you guys can ignore the ScriptManager function. I already try to delete it.

         DataTable CountriesDT = DataRepository.CountryProvider.CountriesGetAll().Tables[0];
            DDLCountry.Items.Add(new ListItem(Translate(Tag.SELECT), "0"));
            DDLInvoiceCountry.Items.Add(new ListItem(Translate(Tag.SELECT), "0"));
            if (CountriesDT != null)
            {
                for (int k = 0; k < CountriesDT.Rows.Count; k++)
                {
                    ListItem myListItem = new ListItem(CountriesDT.Rows[k]["CountryName"].ToString(), CountriesDT.Rows[k]["CountryID"].ToString());
                    ListItem myListInvoiceItem = new ListItem(CountriesDT.Rows[k]["CountryName"].ToString(), CountriesDT.Rows[k]["CountryID"].ToString());
                    DDLCountry.Items.Add(myListItem);
                    DDLInvoiceCountry.Items.Add(myListInvoiceItem);
                }
                ScriptManager.RegisterClientScriptBlock(Page, typeof(Page), "initSelect22", "initSelect2Ddl2();", true);
            }

    function initSelect2Ddl2() {
           $("#<%=DDLCountry.ClientID %>").select2();
           $("#<%=DDLCity.ClientID %>").select2();
        }