README-TUTORIAL-11-INHERITANCE.txt

2:39 AM 2/24/2017	
--Tutorial notes 	
--chuck costarella

The focus of tutorial #11 is OO inheritance in the language and 
how the relational database models those relationships with the TPH (table per hierarchy) structure.

Specifically, the download website 
you are starting with has been modified from the original online tutorial with the following changes:

The Student model has an EmailAddress 
property (a C# string object). EmailAddress is propagated to each of the Student views and works correctly in the website prior to proceeding 
with the tutorial steps. I had added this property to the Student model some time ago when testing the code first approach. I changed the 
Student model to observe the EF picking up my change and modifying my schema correctly to adjust. After that point, I never saw a reason
 to remove email from the Student model, so I left it in there.

So for this tutorial, because of the presence of email address in the
Student model, there are additional changes that must be made that are not part of the tutorial in order to preserve the Student
 EmailAddress property, as follows:

1 - When you are instructed to overwrite the code in the Student.cs file, after you do that,
 you must add the email back into the model class with the following code:

public string EmailAddress { get; set; }

I didn't have 
any data annotations over this prop.

2 - Where you give the EntityFramework PM Console command Add-Migration Inheritance, this
 creates a migration file with the timestamp prepended to its name. You are then given instructions to open this file and edit
 the entityframework code that merges the inheritance hierarchy of base class Person, derived classes Student and Instructor
 back into the Person table (remember TPH is 1 table per hierarchy, in this case Person).

You must add a line of code to the Up() 
method to tell the EntityFramework to create a column for EmailAddress, and then subsequently copy all the Student email data into 
the column in the Person table and allow Null addresses for those Person(s) who don't have them (Instructors do not have them).


Here are the required lines of code:

// put the following command in the same group as the 
AddColumn commands:

AddColumn("dbo.Person", "EmailAddress", c => c.String(nullable: true, maxLength: 128));


The next fragment copies all the student data in to the Person table (preparing to drop the Student table). 
The EMailAddress is added as a named parameter, but make sure it is in the same position on both sides of the 
expression's "SELECT" keyword.

// Copy existing Student data into
 new Person table.
Sql("INSERT INTO dbo.Person (LastName, FirstName, EmailAddress, HireDate, EnrollmentDate, Discriminator, OldId)
 SELECT LastName, FirstName, EmailAddress, null AS HireDate, EnrollmentDate, 'Student' AS Discriminator, ID AS OldId FROM dbo.Student");