c# - 我可以在 DbContext 的 ViewModel 中使用依赖注入(inject)吗？核心2.0

Question

我正在尝试将应用程序从框架项目迁移到 Core 2.0。我遇到的问题与 this one 非常相似，但我正在尝试使用 DI。我根据该问题创建了一个示例项目，但使用的 View 模型类似于我在项目中使用它的方式。我一直在试图弄清楚我在一天多的时间里做错了什么，所以希望这里有人可以提供帮助。

In case It's helpful code on github

在做了一些研究之后，我根据这篇文章中的评论改变了我的应用程序使用我的 View 模型的方式，并开始使用存储库模式。我更新了 git hub 示例以反射(reflect)我的更改，以防它对任何人有所帮助。

ApplicationDbContext.cs

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
    public DbSet<Gig> Gigs { get; set; }
    public ApplicationDbContext(DbContextOptions<ApplicationDbContext> options)
        : base(options)
    {
    }

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

    public DbSet<gigs2.Models.Gig> Gig { get; set; }
}

GigsController.cs

public class GigsController : Controller
{
    // GET: Gigs
    public ActionResult Index()
    {
        GigsViewModel vm = new GigsViewModel();
        vm.Get();
        return View(vm);
    }
}

我在它说的 new GigsViewModel(); 上出错了，因为我需要将选项传递给 ApplicationDbContext

There is no argument given that corresponds to the required formal parameter 'options' of 'ApplicationDbContext.ApplicationDbContext(DbContextOptions)'

GigsViewModels.cs

 public class GigsViewModel
{
    private ApplicationDbContext _context;

    public GigsViewModel(ApplicationDbContext context) {
        _context = context;

    }
    public List<GigViewModel> Gigs { get; set; }

    public void Get()
    {
        Gigs = _context.Gigs.Select(g => new GigViewModel {
            Id = g.Id,
            Date = g.Date,
            Time = g.Time,
            Venue = g.Venue
        }).ToList();
    }
}

启动.cs

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

        services.AddIdentity<ApplicationUser, IdentityRole>(options =>
        {
            options.User.AllowedUserNameCharacters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!#$%&'*+-/=?^_`{|}~.@ ";
            options.User.RequireUniqueEmail = false;
            options.Password.RequireDigit = false;
            options.Password.RequiredLength = 4;
            options.Password.RequireDigit = false;
            options.Password.RequireNonAlphanumeric = false;
            options.Password.RequireUppercase = false;
            options.Password.RequireLowercase = false;
        })
            .AddEntityFrameworkStores<ApplicationDbContext>()
            .AddDefaultTokenProviders();
        services.AddScoped<UserManager<ApplicationUser>, ApplicationUserManager>();
        services.AddScoped<SignInManager<ApplicationUser>, ApplicationSignInManager<ApplicationUser>>();
        services.Configure<Configuration.cofAuthSettings>(Configuration.GetSection("cofAuthSettings"));


        // Add application services.
        services.AddTransient<IEmailSender, EmailSender>();

        services.AddMvc();
    }

Answer 1

将构造函数添加到您的 GigsController接受你的 GigsViewModel 实例的类.这将允许 IoC 容器构建依赖关系树(而不是像现在这样自己创建它。

像这样的东西应该工作:

private readonly GigsViewModel _gigsViewModel;

public GigsController(GigsViewModel gigsViewModel)
{
    _gigsViewModel = gigsViewModel;
}

// GET: Gigs
public ActionResult Index()
{
    _gigsViewModel.Get();
    return View(_gigsViewModel);
}