entity framework - EF Code First Parent-Child insertions with identity columns

Question

i have the following model.

class Parent
{
    int ParentId (identity column) { get; set; }
    string ParentName { get; set; }
    virtual ICollection<Child> Children { get; set; }
}

class Child
{
    int ChildId (identity column) { get; set; }
    string ChildName { get; set; }
    int ParentID { get ; set; } //foreign key to Parent(ParentID)
}

How do i insert few rows to my parent and child in single transaction? Basically i want to get the identity generated on the parent(say i insert a row in parent) and insert child rows with that value? How this can be achieved using Code First?

Answer 1

You shouldn't worry about what value the Id of Parent will get in order to insert Child rows. This should be enough:

var parent = new Parent
{
    // fill other properties

    Children = new List<Child>()
}

parent.Children.add(new Child { /*fill values */);

dbContext.Parents.Add(parent); // whatever your context is named
dbContext.SaveChanges();

For the record, the ID's will be assigned after calling SaveChanges(), so if you really need the ID before inserting a Child entity you can always call SaveChanges() twice.

Again, this shouldn't be necessary though.

By the way, I would recommend making the Foreign Key property from Child to Parent a navigation property, so the Child class would look like:

class Child
{
    public int ChildId { get; set; } // identity column
    public string ChildName { get; set; }
    public virtual Parent Parent { get ; set; } //foreign key to Parent
}

That way you can always access the Child's parent directly without having to retrieve it explicitly from the database yourself (it will be lazy loaded).