C#

public class StaffMember
{
    virtual public string Name { get; set; }
}

public class StaffMemberOracle : StaffMember
{
    [SomeAttribute]
    override public string Name { get; set; }
}

public StaffMember LoadStaffMember(int id)
{
   // Returns instances of derives classes like StaffMemberOracle.
   // Even though the declared return type is "StaffMember", if you
   // return an instance of StaffMemberOracle, the attribute on the
   // Name property is present.
   switch (DB)
   {
      case "Oracle": return OracleDAL.LoadStaffMember(id);
      case "MSSQL": return MssqlDAL.LoadStaffMember(id);
      ...
   }
}

public StaffMember LoadStaffMember(int id)
{
   return CreateDAL().LoadStaffMember(id);
}

public Something LoadSomething(int id)
{
   return CreateDAL().LoadSomething(id);
}

IDAL CreateDAL()
{
   get
   {
     switch (DB)
     {
        case "O": return new OracleDAL();
        case "MS": return new MsSqlDAL();
        ...
     }
   }
}

public class StaffMember
{
    protected int staffID;

    virtual public int StaffID
    {
        get { return staffID; }
        set { staffID = value }
    }
}

public class StaffMemberOracle : StaffMember, INullable, IOracleCustomType 
{
    [OracleObjectMappingAttribute("STAFFID")]
    override void int StaffID
    {
        get { return staffID; }
        set { staffID = value }
    }
}

foreach (string checkedval in this.checkedListBox1.CheckedItems)
{
   // checkedval will hold all the checkboxitems checked.
}