//接口
public interface IPersonalService
{
   //接口中的方法
   PersonalDTO QueryByUid(int uId);
}
//接口派生類
public class PersonalService : IPersonalService
{
    //派生類中實現(xiàn)接口方法--隱式實現(xiàn)
    public PersonalDTO QueryByUid(int uId)
    {
      return _dal.QueryByUid(uId);
    }
    //派生類中調(diào)用接口方法
    public void GetInfo(int userId)
    {
      //調(diào)用方式一
      IPersonalService p = new PersonalService();
      PersonalDTO dto = p.QueryByUid(userId);
      //調(diào)用方式二
      PersonalService p2 = new PersonalService();
      IPersonalService p3 = (IPersonalService)p2;
      PersonalDTO dto = p3.QueryByUid(userId);
    }
}

public IPersonalService pService{get;set;}
public void getInfo()
{
    pService.getInfo();
}