In this lesson, we'll add Identity to our to do list. We will follow the process for adding authentication to an existing .NET application.

Identity Setup and Configuration

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Extending Identity Classes

Let's start by creating a class to represent user accounts. Fortunately, Identity comes with a class to represent users called IdentityUser. As we can see in the IdentityUser documentation entry, this class contains a number of properties such as Emails, UserNames, and many other properties including the number of recorded failed login attempts.

We'll implement this functionality by creating our own custom class that extends from IdentityUser.

Add a file named ApplicationUser.cs to Models. It should contain the following code:

using Microsoft.AspNetCore.Identity;

namespace ToDoList.Models
{
    public class ApplicationUser : IdentityUser
    {

    }
}

We extend Identity's IdentityUser class into our own ApplicationUser class using the : operator in the class declaration. This ensures our ApplicationUser class inherits all necessary functionality from Identity.

Configuring Identity to Work with Entity

Identity is built to use Entity Framework and store user information in a database. It comes with the class IdentityDbContext, which extends Entity Framework's DbContext class to work with user authentication.

First, we'll need to include the package that connects the two:

$ dotnet add package Microsoft.AspNetCore.Identity.EntityFrameworkCore -v 5.0.0

We'll update ToDoListContext.cs so that it extends from IdentityDbContext:

using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;

namespace ToDoList.Models
{
    public class ToDoListContext : IdentityDbContext<ApplicationUser>
    {
      // Don't change code in here.
    }
}

• We'll have to add a new using directive: using Microsoft.AspNetCore.Identity.EntityFrameworkCore;

• Once again, we extend a class with the : operator. We're instructing our ToDoListContext class to inherit all functionality from Identity's built-in IdentityDbContext class. This replaces the DbContext class that ToDoListContext was previously extending from.

• Notice that we're declaring ApplicationUser as the type of IdentityDbContext we're inheriting in the class declaration. This tells Identity which class in the application will contain the user account information it will be responsible for authenticating.

Configuring Startup

Finally, let's update our Startup.cs file and configure the application to use Identity with Entity Framework and MVC.

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using ToDoList.Models;
//new code
using Microsoft.AspNetCore.Identity;

namespace ToDoList
{
  public class Startup
  {
    public Startup(IWebHostEnvironment env)
    {
      var builder = new ConfigurationBuilder()
          .SetBasePath(env.ContentRootPath)
          .AddJsonFile("appsettings.json");
      Configuration = builder.Build();
    }

    public IConfigurationRoot Configuration { get; set; }

    public void ConfigureServices(IServiceCollection services)
    {
      services.AddMvc();

      services.AddEntityFrameworkMySql()
        .AddDbContext<ToDoListContext>(options => options
        .UseMySql(Configuration["ConnectionStrings:DefaultConnection"], ServerVersion.AutoDetect(Configuration["ConnectionStrings:DefaultConnection"])));

      //new code
      services.AddIdentity<ApplicationUser, IdentityRole>()
                .AddEntityFrameworkStores<ToDoListContext>()
                .AddDefaultTokenProviders();
    }

    public void Configure(IApplicationBuilder app)
    {
      app.UseDeveloperExceptionPage();

      //new code
      app.UseAuthentication(); 

      app.UseRouting();

      //new code
      app.UseAuthorization();

      app.UseEndpoints(routes =>
      {
        routes.MapControllerRoute("default", "{controller=Home}/{action=Index}/{id?}");
      });

      app.UseStaticFiles();

      app.Run(async (context) =>
      {
        await context.Response.WriteAsync("Hello World!");
      });
    }
  }
}

• We add the using statement using Microsoft.AspNetCore.Identity; so our Startup class has access to Identity.

• We also tell Identity what we want to use as a model for our user with the line services.AddIdentity<ApplicationUser, IdentityRole>().

• The order of the code in the Configure() method matters. If app.UseAuthentication(), app.UseRouting(), or any other methods are called in the wrong order, you may run into unhandled exceptions or issues logging in. See the Microsoft docs on middleware for more info.

Run Migrations

Now that the project is configured to use Identity, build the project and run the migration commands in the command prompt within the project folder:

$ dotnet ef migrations add addIdentity
$ dotnet ef database update

Repository Reference

Follow the link below to view how a sample version of the project should look at this point. Note that this is a link to a specific commit in the repository.

Example GitHub Repo for To Do List