What is a Discriminator column in ASP.NET Migrations?

Question

I needed to add an extra field to Role identity table in ASP.NET MVC 5.

I use migrations.

I have added an extension to role like:

public cla         


        

Answer 1

Well, a quick answer to understand, or, at least, make it more clear.

As Jasen told, you can read about Table per Hierarchy (TPH) at http://weblogs.asp.net/manavi/inheritance-mapping-strategies-with-entity-framework-code-first-ctp5-part-1-table-per-hierarchy-tph or any other links. But, to tell the truth, it's not so easy to understand from the first time.

Here is a quick answer:

1. Try to create a new role, using ApplicationRole (the class, that was posted in question), inherited from IdentityRole
2. After you create a new role, take a look on Discrimination fields.

As you'll see - the new record contains "ApplicationRole" in the Discrimination column. So to say - that column contains the name of the new class, that inherits IdentityRole. So, there probably can be more classes, which will be inheriting IdentityRole, but for each record the Identity system will store the value - using which class the record was created.

As shown, ApplicationRole Discriminator appeared only for the record, created by the class, called ApplicationRole that inherits IdentityRole.