How to clear dropdownlist OnSelectedIndexChanged in asp.net c#

<asp:DropDownList ID="ddlCity" runat="server" DataValueField="Id" DataTextField="Name"
OnSelectedIndexChanged="ddlCity_SelectedIndexChanged" AutoPostBack="true" >
 </asp:DropDownList>

protected void ddlCountry_SelectedIndexChanged

                      (object sender, EventArgs e)
{
  if (ddlCountry.SelectedValue == "0")
  {
    ddlCity.Items.Clear();
    ddlCity.BindDataSource(null, "Select");
  }
  else
  {

    var city = (from c in "collection or list" select new

               { Id = c.Id, Name = c.Name }).ToList();
    ddlCity.BindDataSource(city, "Select");
  }

}