I believe what Hammad means is that you create a class library for example,
with all of your business logic in it, reference this in your web service and
make the calls through it.

So you'd have something like this in your WS...

..............................................
private MyBusinessComponent oBusiness ;

public MyWebService
{
      oBusiness = new MyBusinessComponent() ;
}

[WebMethod]
public bool SaveBusinessObject(object oObject)
{
    oBusiness.SaveBusinessObject(oObject) ;
}
..............................................

rather than...

..............................................
private MyBusinessComponent oBusiness ;

public MyWebService
{
}

[WebMethod]
public bool SaveBusinessObject(object oObject)
{
   ValidateObject() ;
   MySQLCommand.Execute(sqlString) ;
}
..............................................