How to implement Interfaces in the Data access layer?

 

using ConsoleApplication8.BusinessLayer;
using 
ConsoleApplication8.DataAccessLayer ;
using System.Data ;
using System 
;

Namespace DataAccessLayer 

{

    Public Class CountryGateway : 
ICountryGateway 
     {      
        public 
void InitCountry() 

         {

             //write 
code 

         }

                
        public 
Int32 saveCountry(ByRef obj As Country) 

      {

            //write 
code 

      }


        // 
        //implementation 
for other methods SearchByIndex() SearchByName and 
UpdateCountry() 
        //
        //

   }

    Interface 
ICountryGateway {
        void 
InitCountry() ;
        Int32 
saveCountry(ref obj As 
Country) ;
        DataSet 
SearchByIndex(countryNo As 
String)
        DataSet 
SearchByName(countryName As 
String);
        Int32 
updateCountry(ref country As 
Country);
    }




}

Namespace 
BusinessLayer {

    Public Class Country 
{

    }


}