Add custom column in AspNetRoles results in Invalid Column Name Discriminator - asp.net-mvc

Question

I'm using ASP.NET MVC5 with Identity 2 framework, Database first
I'm trying to custom AspNetRoles, by adding a column called MyCustomColumn
However, my app crashes because :
Invalid Column Name Discriminator
There is a lot of resources on SO and elsewhere on the web, but most of them are with CodeFirst approach and I can't use them in my app.
How to deal with it ?

Answer 1

Actually, none of this is necessary. Most likely you failed to update your context to inherit from IdentityDbContext<TUser, TRole, TKey, TUserLogin, TUserRole, TUserClaim>, rather than the default of IdentityDbContext<TUser>. Since you did not pass your custom role entity as the TRole type parameter, the context instead uses IdentityRole as the class type. It then creates a table for IdentityRole, sees that your custom role inherits from IdentityRole, and therefore adds the Discriminator column so that it can tell the different between an instance of IdentityRole and your custom role, in the database (single table inheritance is the default strategy EF employs).
This will technically work, but your custom role will never actually be utilized. Use the right generic abstract context class, and you'll be fine.
For what it's worth, you should do away with the EDMX stuff, as well. It's deprecated, buggy, and unnecessary. Despite the name, "Code First" can be used with an existing database or to create a new one.
DON'T
public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
DO
public class ApplicationDbContext : IdentityDbContext<ApplicationUser, CustomRole, string, IdentityUserLogin, IdentityUserRole, IdentityUserClaim>

Answer 2

Ok, as I spend some hours to find a solution, I post it here, if it could help someone else.
First, in AspNetRoles, create your custom column AND a column called Discriminator (which is a nvarchar(max) ). Update your .edmx
Then, we have to create a class which inherits from IdentityRole. We will use this class to access our custom column we just created :
In Models folder
public ApplicationRole()
: base() { }
public ApplicationRole(string name, long myCustomValue)
: base(name)
{
MyCustomValue = myCustomValue;
}
public virtual long MyCustomValue { get; set; }
Then, let's create a class which inherits from RoleManager<ApplicationRole>.
I placed it in IdentityConfig.cs, but maybe it's a best practice to place it elsewhere...
For information, I get inspired by this blog, Re-Implementing RoleStore and ApplicationRoleManager paragraph
public class ApplicationRoleManager : RoleManager<ApplicationRole>
{
public ApplicationRoleManager(
IRoleStore<ApplicationRole, string> roleStore)
: base(roleStore)
{
}
public static ApplicationRoleManager Create(
IdentityFactoryOptions<ApplicationRoleManager> options, IOwinContext context)
{
return new ApplicationRoleManager(
new RoleStore<ApplicationRole>(context.Get<ApplicationDbContext>()));
}
}
ApplicationRoleManager has a constructor which calls our previously created ApplicationRole class.
Now we have to register our ApplicationRoleManager at startup, so we have to add this line after the others CreatePerOwinContext
In App_Start\Startup.auth.cs, ConfigureAuth(IAppBuilder app) method
app.CreatePerOwinContext<ApplicationRoleManager>(ApplicationRoleManager.Create);
So now we can use our ApplicationRoleManager, correctly instanciated :
var rm = new ApplicationRoleManager(new RoleStore<ApplicationRole>(new ApplicationDbContext()));
And then use it as we want
var roleName = rm.FindByName("Admin");
string myCustomData = roleName.CustomData.ToString();