SignInManager.PasswordSignInAsync の「この DbContext にはデータベース プロバイダーが設定されていません」質問する

次のエラー メッセージが表示されます。

InvalidOperationException: この DbContext にはデータベース プロバイダーが構成されていません。プロバイダーは、DbContext.OnConfiguring メソッドをオーバーライドするか、アプリケーション サービス プロバイダーで AddDbContext を使用することによって構成できます。AddDbContext を使用する場合は、DbContext 型がコンストラクターで DbContextOptions オブジェクトを受け入れ、それを DbContext の基本コンストラクターに渡すことも確認してください。

Startup.cs は次のとおりです。

public void ConfigureServices(IServiceCollection services)
    {
        services.Configure<AppSettings>(Configuration.GetSection("AppSettings"));

        // Add EF services to the services container.
        services.AddEntityFrameworkSqlServer()
           .AddDbContext<LogManagerContext>(options =>
              options.UseSqlServer(Configuration["Data:DefaultConnection:Connectionstring"]));

        services.AddSingleton(c => Configuration);

        // Add Identity services to the services container.
        services.AddIdentity<ApplicationUser, IdentityRole>()
            .AddEntityFrameworkStores<LogManagerContext>()
            .AddDefaultTokenProviders();
            
        
        // Add MVC services to the services container.
        services.AddMvc();

        services.AddTransient<IHttpContextAccessor, HttpContextAccessor>();

        //Add all SignalR related services to IoC. - Signal R not ready yet - Chad
        //services.AddSignalR();

        //Add InMemoryCache
        services.AddMemoryCache();

        services.AddSession(options =>
        {
            options.IdleTimeout = System.TimeSpan.FromHours(1);
            options.CookieName = ".LogManager";
        });

        // Uncomment the following line to add Web API servcies which makes it easier to port Web API 2 controllers.
        // You need to add Microsoft.AspNet.Mvc.WebApiCompatShim package to project.json
        // services.AddWebApiConventions();
        // Register application services.
        services.AddTransient<IEmailSender, AuthMessageSender>();
        
    }

    // Configure is called after ConfigureServices is called.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
    {
        app.UseSession();

        // Configure the HTTP request pipeline.
        // Add the console logger.
        //loggerFactory.MinimumLevel = LogLevel.Information; - moved to appsettings.json -chad
        loggerFactory.AddConsole();
        loggerFactory.AddDebug();

        loggerFactory.AddNLog();

        // Add the following to the request pipeline only in development environment.
        if (env.IsDevelopment())
        {
            app.UseBrowserLink();
            app.UseDeveloperExceptionPage();
            //app.UseDatabaseErrorPage(DatabaseErrorPageOptions.ShowAll);
        }
        else
        {
            // Add Error handling middleware which catches all application specific errors and
            // sends the request to the following path or controller action.
            app.UseExceptionHandler("/Home/Error");
        }

        env.ConfigureNLog("NLog.config");

        // Add static files to the request pipeline.
        app.UseStaticFiles();

        // Add cookie-based authentication to the request pipeline.
        app.UseIdentity();

        //SignalR
        //app.UseSignalR();

        // Add MVC to the request pipeline.
        app.UseMvc(routes =>
        {
            routes.MapRoute(
             name: "default",
             template: "{controller}/{action}/{id?}",
             defaults: new { controller = "Home", action = "Index" }
             );

            // Uncomment the following line to add a route for porting Web API 2 controllers.
            // routes.MapWebApiRoute("DefaultApi", "api/{controller}/{id?}");
        });
    }

public class ApplicationUser : IdentityUser
{
    // Add Custom Profile Fields
    public string Name { get; set; }
}

public class LogManagerContext : IdentityDbContext<ApplicationUser>
{
    public DbSet<LogEvent> LogEvents { get; set; }
    public DbSet<Client> Clients { get; set; }
    public DbSet<LogEventsHistory> LogEventsHistory { get; set; }
    public DbSet<LogEventsLineHistory> LogEventsLineHistory { get; set; }
    public DbSet<LogRallyHistory> LogRallyHistory { get; set; }
    public DbSet<Flag> Flags { get; set; }
    protected override void OnModelCreating(ModelBuilder builder)
    {

        builder.Entity<LogEvent>().HasKey(x => x.LogId);
        builder.Entity<LogEvent>().ToTable("LogEvents");
        builder.Entity<Client>().HasKey(x => x.ClientId);
        builder.Entity<Client>().ToTable("Clients");
        builder.Entity<LogEventsHistory>().HasKey(x => x.HistoryId);
        builder.Entity<Flag>().HasKey(x => x.FlagId);
        builder.Entity<Flag>().ToTable("Flags");
        builder.Entity<LogRallyHistory>().HasKey(x => x.HistoryId);
        builder.Entity<LogEventsLineHistory>().HasKey(x => x.LineHistoryId);

        base.OnModelCreating(builder);
    }