Cant get my dropdownlist on indexchange to execute code

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                average(DropDownList1.SelectedValue.ToString());
                count(DropDownList1.SelectedValue.ToString());
            }
        }

my dropdownlist wont execute I have tried to autopostback in the webcode but that wont work ither.