In which layer to make linq-sql calls as SubmitChanges(), InsertOnSubmit() etc

Question

Which layer is the best layer to make linq-sql calls as SubmitChanges(), InsertOnSubmit() etc.

For example, let's say I have two tables Parent and Child. Child table has foreign key on parent (Child table has ParentId column). I want to insert parent object and child objects into the db.

Using linq-sql, I can do this.

Parent parent = new Parent();
Child child1 = new Child();
Child child2 = new Child();
//assign values to parent data members
//...

parent.Childs.Add(child1);
parent.Childs.Add(child2);

using (DataContext db = new DataContext())
{
   db.Parents.InsertOnSubmit(parent);
   db.SubmitOnChanges();  
}

Am I mixing Presentation layer code with data access layer? If so, how do I do it with a business layer object in between?

Please let me know. Thanks.

Answer 1

Having the data access right there within the presentation layer is probably not the best way to do it.

You could implement a Writer class which has methods that access the DataContext.

Parent parent = new Parent();
Child child1 = new Child();
Child child2 = new Child();
//assign values to parent data members
//...

parent.Childs.Add(child1);
parent.Childs.Add(child2);    

using (var parentWriter = new ParentWriter())
{
  parentWriter.Insert(parent)
}

Then in the wrapper class

public class ParentWriter : IDisposable
{
  private DataContext _dc;

  public ParentWriter()
  {
    _dc = new DataContext();
  }

  public void Insert(Parent parent)
  {
    _dc.Parents.InsertOnSubmit(parent);
    _dc.SubmitOnChanges();
  }

  //IDisposable Members
  //...
}

This is quite a simplified example and is untested. I have used a similar design in a recent project where we have specific Writer and Reader classes that split the data access depending on what we're doing with the data.