How to seed an Admin user in EF Core 2.1.0?

As user cannot be seeded in a normal way in Identity just like other tables are seeded using .HasData() of .NET Core 2.1.

Microsoft Recommendation: For data that requires calls to external API, such as ASP.NET Core Identity users creation it is recommended to use custom initialization logic.

Seed Roles in .NET Core 2.1 using code given below in ApplicationDbContext Class :

protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        base.OnModelCreating(modelBuilder);
        // Customize the ASP.NET Identity model and override the defaults if needed.
        // For example, you can rename the ASP.NET Identity table names and more.
        // Add your customizations after calling base.OnModelCreating(builder);

        modelBuilder.Entity<IdentityRole>().HasData(new IdentityRole { Name = "Admin", NormalizedName = "Admin".ToUpper() });
    }

Seed Users With Roles by Following the steps given below.

Step 1: New class creation

public static class ApplicationDbInitializer
{
    public static void SeedUsers(UserManager<IdentityUser> userManager)
    {
        if (userManager.FindByEmailAsync("[email protected]").Result==null)
        {
            IdentityUser user = new IdentityUser
            {
                UserName = "[email protected]",
                Email = "[email protected]"
            };

            IdentityResult result = userManager.CreateAsync(user, "PasswordHere").Result;

            if (result.Succeeded)
            {
                userManager.AddToRoleAsync(user, "Admin").Wait();
            }
        }       
    }   
}

Step 2: Now Modify ConfigureServices method in Startup.cs class.

Before Modification:

services.AddDefaultIdentity<IdentityUser>()
            .AddEntityFrameworkStores<ApplicationDbContext>();

After Modification:

services.AddDefaultIdentity<IdentityUser>().AddRoles<IdentityRole>()
            .AddEntityFrameworkStores<ApplicationDbContext>();

Step 3: Modify parameters of Configure Method in Startup.cs class.

Before Modification :

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        //..........
    }

After modification :

public void Configure(IApplicationBuilder app, IHostingEnvironment env, UserManager<IdentityUser> userManager)
    {
        //..........
    }

Step 4 : Calling method of our Seed (ApplicationDbInitializer) class:

ApplicationDbInitializer.SeedUsers(userManager);

Note: You can also Seed Roles just like users by Injecting the RoleManager along with UserManager.

Actually a User Entity can be seeded in OnModelCreating, one thing to consider: the IDs should be predefined. If type string is used for TKey identity entities, then there is no problem at all.

protected override void OnModelCreating(ModelBuilder builder)
{
    base.OnModelCreating(builder);
    // any guid
    const string ADMIN_ID = "a18be9c0-aa65-4af8-bd17-00bd9344e575";
    // any guid, but nothing is against to use the same one
    const string ROLE_ID = ADMIN_ID;
    builder.Entity<IdentityRole>().HasData(new IdentityRole
    {
        Id = ROLE_ID,
        Name = "admin",
        NormalizedName = "admin"
    });

    var hasher = new PasswordHasher<UserEntity>();
    builder.Entity<UserEntity>().HasData(new UserEntity
    {
        Id = ADMIN_ID,
        UserName = "admin",
        NormalizedUserName = "admin",
        Email = "[email protected]",
        NormalizedEmail = "[email protected]",
        EmailConfirmed = true,
        PasswordHash = hasher.HashPassword(null, "SOME_ADMIN_PLAIN_PASSWORD"),
        SecurityStamp = string.Empty
    });

    builder.Entity<IdentityUserRole<string>>().HasData(new IdentityUserRole<string>
    {
        RoleId = ROLE_ID,
        UserId = ADMIN_ID
    });
}