Empty value in the drop downlist

Dear all,
If the datavalue which is empty and not exist in the dropdownlist data source, it will prompt error. How to overcome??
I want it will show 'Select Country' when data value is empty or is null.
 
<asp:DropDownList ID = "ddllabelCountry"
                      DataSourceID="objCountry"
                      DataTextField="CountryName"
                      DataValueField="CountryCode"
                      EnableViewState="true"
  & ...