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?
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.