Question

If you have, for example, a database table called Person (ID,Name etc) what kind of object should the data access tier return to the business tier? I’m thinking something like this:

//data access tier public class DataAccess{     public interface IPerson{       int ID{ get; set; }       string Name{ get; set; }    }     internal class Person : IPerson{       private int id;       private string name;        public int ID{ get{return id; } set{ id=value; } }       public int Name{ get{retutn name; } set{ name=value; }    }     public static IPerson GetPerson(int personId)    {       //get person record from db, populate Person object       return person;      } }  //business tier public class Person : IPerson{    private int id;    private string name;     public int ID{ get{return id;} set{id=value;} }    public string Name{ get{return name;} set{name=value;} }     public void Populate(int personId){       IPerson temp = DataAccess.GetPerson(personId);       this.ID = temp.ID;       this.Name = temp.Name;    } } 

But this all seems a little cumbersome? Is there a more elegant solution to this problem? Should I return a DataRow from the data access layer to the business layer instead?

Answer 1

You don’t need to repeat the class definition in your data access layer (DAL).

You can create your business entities as ‘dumb’ containers in a separate assembly, e.g. your Person class can just be:-

public class Person {     int ID { get; set: }     string Name { get; set: } } 

Then, you can give your DAL a reference to the business entities layer. Your controller objects, whether they are in a separate business logic layer, or within your UI layer, can then just call the DAL, which can create a business entity, populate it from the database and return it to your controller.

This article by Imar Spaanjaars has a nice explanation of this pattern.