.net core 2.0 - Value cannot be null. Parameter name: key

Question

I have such error in package manager console when Add-Migration

Entity Framework Core 2.0.1-rtm-125 initialized 'ApplicationDbContext' using provider 'Microsoft.EntityFrameworkCore.SqlServer' with options: MigrationsAssembly=Project.Data 
System.ArgumentNullException: Value cannot be null.
Parameter name: key
at Microsoft.EntityFrameworkCore.Utilities.Check.NotNull[T](T value, String parameterName)
   at Microsoft.EntityFrameworkCore.RelationalMetadataExtensions.Relational(IKey key)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.<Add>d__35.MoveNext()
   at System.Linq.Enumerable.<CastIterator>d__34`1.MoveNext()
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.<Add>d__26.MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.<DiffCollection>d__50`1.MoveNext()
   at System.Linq.Enumerable.ConcatIterator`1.MoveNext()
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Sort(IEnumerable`1 operations, DiffContext diffContext)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.GetDifferences(IModel source, IModel target)
   at Microsoft.EntityFrameworkCore.Migrations.Design.MigrationsScaffolder.ScaffoldMigration(String migrationName, String rootNamespace, String subNamespace)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_1.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Value cannot be null.
Parameter name: key

I'm trying to add Organization entity:

public class Organization 
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    public string Name { get; set; }
}

This is my AppDbContext

public class ApplicationDbContext : IdentityUserContext<AppUser>
{
    public virtual DbSet<Organization> Organizations { get; set; }

    public ApplicationDbContext(DbContextOptions options)
        : base(options)
    {

    }

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

When I run application, it works fine, but when I'm trying to add migration it tells me that parameter name - key can't be null. Can someone please shed some lights here? Thanks

This is my Startup code

    public class Startup
{
    public IConfiguration _configuration { get; }

    // Inject project configuration
    public Startup(IConfiguration configuration)
    {
        _configuration = configuration;
    }

    // This method gets called by the runtime.
    // Use this method to add services to the conteiner.
    public void ConfigureServices(IServiceCollection services)
    {
        #region Database

        // Add Database Context
        services.AddDatabase(_configuration);

        #endregion

        ...

        #region Identity
        // Add Identity 
        // TODO: Extract to external extension method .AddIdentity()
        var builder = services.AddIdentityCore<AppUser>(o =>
        {
            // Configure Identity options
            o.Password.RequireDigit = false;
            o.Password.RequireLowercase = false;
            o.Password.RequireUppercase = false;
            o.Password.RequireNonAlphanumeric = false;
            o.Password.RequiredLength = 6;
        });
        builder = new IdentityBuilder(builder.UserType, typeof(IdentityRole), builder.Services);
        builder.AddEntityFrameworkStores<ApplicationDbContext>().AddDefaultTokenProviders();
        #endregion

        ...            

        services.AddAutoMapper();
        services.AddMvc();
    }

    // This method gets called by the runtime.
    // Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    {
        // TODO: Add development configuration
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseAuthentication();

        ...            

        // Configure application for usage as API
        // with default route of '/api/[Controller]'
        app.UseMvcWithDefaultRoute();

        // Configures application to serve the index.html file from /wwwroot
        // when you access the server from a browser
        app.UseDefaultFiles();
        app.UseStaticFiles();
    }
}

Answer 1

1. Shouldn't the dbContext be called IdentityDbContext<AppUser> not IdentityUserContext<AppUser>?

2. Shouldn't the constructor of ApplicationDbContext take the DbContextOptions of the type ApplicationDbContext?

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

3. You don't need virtual keyword do you?

   public DbSet<Organization> Organizations { get; set; }
   

4. Use AddIdentity instead?

   services.AddIdentity<AppUser, AppRole>(options =>
       options.User.RequireUniqueEmail = true/false;
   
       options.Password.RequireDigit = true/false;
       ...
   })
   .AddEntityFrameworkStores<ApplicationDbContext>()
   // Components that generate confirm email and reset password tokens.
   .AddDefaultTokenProviders();
   

I don't know where you got the code from but it's kind of messy and hard to read.