Why does linq-2-sql create extra unnecessary objects?

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I have a simple Parent Child table in a database like so

CREATE TABLE [Parent](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Name] [nvarchar](256) NOT NULL)    
ALTER TABLE [Parent] ADD CONSTRAINT [PK_Parent_Id] PRIMARY KEY ([Id])    

CREATE TABLE [Child](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [ParentId] [int] NOT NULL,
    [Name] [nvarchar](256) NOT NULL)    
ALTER TABLE [Child] ADD CONSTRAINT [PK_Child_Id] PRIMARY KEY ([Id])
ALTER TABLE [Child] ADD CONSTRAINT [FK_Child_Parent_ID] 
    FOREIGN KEY([ParentId]) REFERENCES [Parent] ([Id])

The data that I have in them is

Parent Table

Id  Name
1   John

Child Table

Id ParentId  Name
1     1    Mike
2     1    Jake
3     1    Sue
4     1    Liz

These tables are mapped to Parent and Child C# objects using the Linq-2-SQL designer in Visual Studio with no non standard options.

I made a simple test program to query all child with their parents

public partial class Parent
{
    static int counter = 0;
    //default OnCreated created by the linq to sql designer
    partial void OnCreated()
    {
        Console.WriteLine(string.Format("CreatedParent {0} hashcode={1}",
            ++counter , GetHashCode()));
    }
}

class Program
{
    static void Main(string[] args)
    {
        using (var db = new SimpleDbDataContext())
        {
            DataLoadOptions opts = new DataLoadOptions();
            opts.LoadWith<Child>(c => c.Parent);
            db.LoadOptions = opts;
            var allChildren = db.Childs.ToArray();
            foreach (var child in allChildren)
            {
                Console.WriteLine(string.Format("Parent name={0} hashcode={1}",
                    child.Parent.Name, child.Parent.GetHashCode()));

            }
        }
    }
}

The output of the above program is

CreatedParent 1 hashcode=53937671
CreatedParent 2 hashcode=9874138
CreatedParent 3 hashcode=2186493
CreatedParent 4 hashcode=22537358
Parent name=John hashcode=53937671
Parent name=John hashcode=53937671
Parent name=John hashcode=53937671
Parent name=John hashcode=53937671

As you can see a Parent object was created for every Child in the database only to be discarded eventually.

Questions:

  1. Why does Linq-2-Sql create these unnecessary extra Parent objects ?
  2. Are there any options to avoid creation of extra Parent objects ?
1 Answers
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