Entity Framework 6 - database di seeding genera System.NullReferenceException

Sto usando .net core 2 e entityframework 6.2. Sto provando a seminare il database con alcuni dati di base necessari.

1. Non ho trovato il metodo Database.SetInitializer. Così ho cercato su Google e ho trovato un altro modo per seminare il mio database nel metodo Main della classe Program (come mostrato di seguito).
2. Ho usato sotto il codice per seminare il mio database ma quando DbContext metodo SaveChange di DbContext , DbContext sempre l'errore NullReferenceException.
3. Sto usando lo stesso database usato da Identity. Influisce sul risultato?

Classe di programma:

public class Program
{
    public static void Main(string[] args)
    {
        //BuildWebHost(args).Run();

        var host = BuildWebHost(args);

        using (var scope = host.Services.CreateScope())
        {
            var services = scope.ServiceProvider;
            try
            {
                var context = services.GetRequiredService<ApplicationDbContext>();
                context.Provinces.Add(new Models.Province
                {
                    ID = 1,
                    Name = "TEST"
                });
                context.SaveChanges(); // <= ERROR
                //DbInitializer.Initialize(context);
            }
            catch (Exception ex)
            {
                var logger = services.GetRequiredService<ILogger<Program>>();
                logger.LogError(ex, "An error occured while seeding the database.");
            }
        }

        host.Run();
    }

    public static IWebHost BuildWebHost(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .UseStartup<Startup>()
            .Build();
}

Eccezione:

Message: "Object reference not set to an instance of an object."
Source: "Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore"
StackTrace:
   at Microsoft.AspNetCore.Diagnostics.EntityFrameworkCore.DatabaseErrorPageMiddleware.System.IObserver<System.Collections.Generic.KeyValuePair<System.String,System.Object>>.OnNext(KeyValuePair`2 keyValuePair)
   at System.Diagnostics.DiagnosticListener.Write(String name, Object value)
   at Microsoft.EntityFrameworkCore.Internal.CoreLoggerExtensions.SaveChangesFailed(IDiagnosticsLogger`1 diagnostics, DbContext context, Exception exception)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChanges(Boolean acceptAllChangesOnSuccess)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChanges()
   at Invitation.Program.Main(String[] args) in d:\Projects\Invitation\Invitation\Program.cs:line 29
InnerException: null

Classe di avvio:

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<ApplicationDbContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

        services.AddCustomIdentity()
            .AddEntityFrameworkStores<ApplicationDbContext>()
            .AddDefaultTokenProviders();

        services.AddTransient<IdentityErrorDescriber, FaIdentityErrorDescriber>();

        services.ConfigureCustomApplicationCookie();

        services.AddAntiforgery(options => options.HeaderName = "X-XSRF-TOKEN");

        services.AddMvc()
            .AddRazorPagesOptions(options =>
            {
                options.Conventions.AuthorizeFolder("/Account/Manage");
                options.Conventions.AuthorizePage("/Account/Logout");
            });

        var connection = Configuration.GetConnectionString("DefaultConnection");
        services.AddDbContext<ApplicationDbContext>(options => options.UseSqlServer(connection));

        services.AddSingleton<IEmailSender, EmailSender>();
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseBrowserLink();
            app.UseDeveloperExceptionPage();
            app.UseDatabaseErrorPage();
        }
        else
        {
            app.UseExceptionHandler("/Error");
        }

        app.UseStaticFiles();

        app.UseAuthentication();

        app.UseMvc();
    }
}

Classe ApplicationDbContext:

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
        : base(options)
    {
    }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);
    }

    public DbSet<Province> Provinces { get; set; }
}

BW sto usando EntityFramework 6.2.0 e Microsoft.EntityFrameworkCore.Tools 2.1.1 (forse informazioni utili)

Grazie per aver passato del tempo.