Multiple Identities in ASP.NET Core 2.0

Question

I am migrating an ASP.NET Core 1.0 application to ASP.NET Core 2.0.

In my startup I am configuring two identities:

services.AddIdentity<IdentityUser, IdentityRole>(configureIdentity)
   .AddDefaultTokenProviders()
   .AddUserStore<IdentityUserStore<IdentityUser>>()
   .AddRoleStore<IdentityRoleStore<IdentityRole>>();

services.AddIdentity<Customer, CustomerRole>(configureIdentity)
   .AddDefaultTokenProviders()
   .AddErrorDescriber<CustomerIdentityErrorDescriber>()
   .AddUserStore<CustomerStore<Customer>>()
   .AddRoleStore<CustomerRoleStore<CustomerRole>>();

This worked fine in ASP.NET Core 1.0 but fails with the error: System.InvalidOperationException: 'Scheme already exists: Identity.Application' in ASP.NET Core 2.0.

In ASP.NET Core 2.0, if I remove one of the calls to AddIdentity the error goes away. How do I migrate my code so that I can use two different types of identity user and role in my application? Or did I just make a fundamental error in understanding how things work back when I wrote this in ASP.NET Core 1.0?

Answer 1

After looking through the ASP.NET Core source code on github, a second identity could be added using this extension method:

using Microsoft.AspNetCore.Identity;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using System;
using System.Collections.Generic;
using System.Text;

namespace Whatever
{
    public static class IdentityExtensions
    {
        public static IdentityBuilder AddSecondIdentity<TUser, TRole>(
            this IServiceCollection services)
            where TUser : class
            where TRole : class
        {
            services.TryAddScoped<IUserValidator<TUser>, UserValidator<TUser>>();
            services.TryAddScoped<IPasswordValidator<TUser>, PasswordValidator<TUser>>();
            services.TryAddScoped<IPasswordHasher<TUser>, PasswordHasher<TUser>>();
            services.TryAddScoped<IRoleValidator<TRole>, RoleValidator<TRole>>();
            services.TryAddScoped<ISecurityStampValidator, SecurityStampValidator<TUser>>();
            services.TryAddScoped<IUserClaimsPrincipalFactory<TUser>, UserClaimsPrincipalFactory<TUser, TRole>>();
            services.TryAddScoped<UserManager<TUser>, AspNetUserManager<TUser>>();
            services.TryAddScoped<SignInManager<TUser>, SignInManager<TUser>>();
            services.TryAddScoped<RoleManager<TRole>, AspNetRoleManager<TRole>>();

            return new IdentityBuilder(typeof(TUser), typeof(TRole), services);
        }
    }
}