SelectedIndex which is invalid because it does not exist in the list of items. Parameter name

See more:

C#

ASP.NET

Hi can any one please me to resolve this issue....that is i'm getting the error as
-----------Error----------------------

{"'DDLShipmentType' has a SelectedIndex which is invalid because it does not exist in the list of items.\r\nParameter name: value"}

------------------------------------------------

near

cmb_ShipmentType.SelectedIndex = 0;

i'm getting the selectedindex as -1 in the below code

public void PopulateShipmentType(DropDownList cmb_ShipmentType)
       {
           string Sql = "select a,b from xxx where NUIsActive=1";
           using (DataView Source = new DataView(objDBLib.ExecuteQuery(Sql).Tables[0]))
           {
               cmb_ShipmentType.DataSource = Source;
               cmb_ShipmentType.DataTextField = "a";
               cmb_ShipmentType.DataValueField = "b";
               cmb_ShipmentType.DataBind();
               
              cmb_ShipmentType.SelectedIndex = 0;
           }
       }