如何將用戶字段設置為當前記錄的用戶ASP.NET MVC的數據庫記錄添加

Question

將類別添加到登錄用戶時出現問題。 我遇到錯誤System.InvalidOperationException: "Sequence has no elements." 。

我的代碼：

public class AppUser
{
    public int Id { get; set; }
    public string Nickname { get; set; }
    public string Name { get; set; }
    public string Surname { get; set; }
    public DateTime BirthDate { get; set; }
    public virtual ICollection<Category> Categories { get; set; }

}

public class Category
{
    public int Id { get; set; }
    public string Name { get; set; }
    public AppUser AppUser { get; set; }
    public int AppUserId { get; set; }

}

public class CategoryAndAppUserViewModel
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int AppUserId { get; set; }
}

// GET: Categories/Create
public ActionResult Create()
{
    return View();
}

我的控制器：

// GET: Categories/Create
public ActionResult Create()
{
    return View();
}

// POST: Categories/Create
[Authorize]
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create(CategoryAndAppUserViewModel category)
{
    if (ModelState.IsValid)
    {

        string userId = User.Identity.GetUserId();
        AppUser appUser = _context.AppUsers.Single(u => u.Name == userId);
        var categoryVM = new Category { Name = category.Name, AppUser = appUser };
        appUser.Categories.Add(categoryVM);
        _context.SaveChanges();
        return RedirectToAction("Index");
    }

    return View(category);
}

我想做的是：當用戶登錄后，轉到“ My Examples ，創建新的Category ，填寫新的類別名稱，應用程序必須自動將新類別添加到已登錄的用戶。 主要問題是獲取登錄的用戶ID。

Answer 1

將類別添加到登錄用戶時出現問題。 我遇到錯誤System.InvalidOperationException: "Sequence has no elements." 。

我的代碼：

public class AppUser
{
    public int Id { get; set; }
    public string Nickname { get; set; }
    public string Name { get; set; }
    public string Surname { get; set; }
    public DateTime BirthDate { get; set; }
    public virtual ICollection<Category> Categories { get; set; }

}

public class Category
{
    public int Id { get; set; }
    public string Name { get; set; }
    public AppUser AppUser { get; set; }
    public int AppUserId { get; set; }

}

public class CategoryAndAppUserViewModel
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int AppUserId { get; set; }
}

// GET: Categories/Create
public ActionResult Create()
{
    return View();
}

我的控制器：

// GET: Categories/Create
public ActionResult Create()
{
    return View();
}

// POST: Categories/Create
[Authorize]
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create(CategoryAndAppUserViewModel category)
{
    if (ModelState.IsValid)
    {

        string userId = User.Identity.GetUserId();
        AppUser appUser = _context.AppUsers.Single(u => u.Name == userId);
        var categoryVM = new Category { Name = category.Name, AppUser = appUser };
        appUser.Categories.Add(categoryVM);
        _context.SaveChanges();
        return RedirectToAction("Index");
    }

    return View(category);
}

我想做的是：當用戶登錄后，轉到“ My Examples ，創建新的Category ，填寫新的類別名稱，應用程序必須自動將新類別添加到已登錄的用戶。 主要問題是獲取登錄的用戶ID。