SQL Server supports the auto-generation of primary key values through the identity setting.  When creating a new LINQ business object, the value of the primary key is zero; meaning no value has been assigned. Calling SubmitChanges on the DataContext refreshes this value with the auto-generated value assigned from the backend database. Let us take a look at an example.

When creating a new business object, the value of the primary key is illustrated below.

Listing 6

Product product = new Product();
product.Name = "Value";

//Assign remaining values.

Listing 7

Assert.AreEqual(0, product.ProductKey);

But after the call to submit changes, the value is updated to:

_context.SubmitChanges();
Assert.AreEqual(6, product.ProductKey);

The product key is assigned to an actual value after the product is refreshed.