上下文 int 实体/网络核心的问题

Question

为我的模型创建控制器后遇到问题。这是主要型号：

public class Event
{
    public int ID { get; set; }
    [Required]
    public string Title { get; set; }
    [Required]
    public string Description { get; set; }
    [DataType(DataType.Date)]
    [Required]
    public DateTime Date { get; set; }

    public Subcategory Subcategory { get; set; }
    public int SubcategoryID { get; set; }

    public Place Place { get; set; }
    public int PlaceID { get; set; }

    public Organisator Organisator { get; set; }
    public int OrganisatorID { get; set; }

    public ICollection<User_link> User_link { get; set; }
}

这里的其他模型，如 Subcategory、Place 和 Organizer 具有一对多（事件）绑定。

这里是地方例如：

public class Place
{
    public int ID { get; set; }
    [Required]
    public string Title { get; set; }
    [Required]
    public string Address { get; set; }
    [Required]
    public string Call_number { get; set; }
    public string Email { get; set; }
    public string Vk { get; set; }
    public string Facebook { get; set; }

    public ICollection<Event> Event { get; set; }
}

所以我在每个地方都有事件的集合。还有事件控制器

public class EventsController : Controller
{
    private readonly ApplicationDbContext _context;

    public EventsController(ApplicationDbContext context)
    {
        _context = context;
    }

    // GET: Events
    public async Task<IActionResult> Index()
    {
        var applicationDbContext = _context.Event.Include(@ => @.Organisator).Include(@ => @.Place).Include(@ => @.Subcategory);
        return View(await applicationDbContext.ToListAsync());
    }

    // GET: Events/Details/5
    public async Task<IActionResult> Details(int? id)
    {
        if (id == null)
        {
            return NotFound();
        }

        var @event = await _context.Event
            .Include(@ => @.Organisator)
            .Include(@ => @.Place)
            .Include(@ => @.Subcategory)
            .SingleOrDefaultAsync(m => m.ID == id);
        if (@event == null)
        {
            return NotFound();
        }

        return View(@event);
    }

    // GET: Events/Create
    public IActionResult Create()
    {
        ViewData["OrganisatorID"] = new SelectList(_context.Organisator, "ID", "Title");
        ViewData["PlaceID"] = new SelectList(_context.Place, "ID", "Address");
        ViewData["SubcategoryID"] = new SelectList(_context.Subcategory, "ID", "Title");
        return View();
    }

    // POST: Events/Create
    // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
    // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> Create([Bind("ID,Title,Description,Date,SubcategoryID,PlaceID,OrganisatorID")] Event @event)
    {
        if (ModelState.IsValid)
        {
            _context.Add(@event);
            await _context.SaveChangesAsync();
            return RedirectToAction(nameof(Index));
        }
        ViewData["OrganisatorID"] = new SelectList(_context.Organisator, "ID", "Title", @event.OrganisatorID);
        ViewData["PlaceID"] = new SelectList(_context.Place, "ID", "Address", @event.PlaceID);
        ViewData["SubcategoryID"] = new SelectList(_context.Subcategory, "ID", "Title", @event.SubcategoryID);
        return View(@event);
    }

    // GET: Events/Edit/5
    public async Task<IActionResult> Edit(int? id)
    {
        if (id == null)
        {
            return NotFound();
        }

        var @event = await _context.Event.SingleOrDefaultAsync(m => m.ID == id);
        if (@event == null)
        {
            return NotFound();
        }
        ViewData["OrganisatorID"] = new SelectList(_context.Organisator, "ID", "Title", @event.OrganisatorID);
        ViewData["PlaceID"] = new SelectList(_context.Place, "ID", "Address", @event.PlaceID);
        ViewData["SubcategoryID"] = new SelectList(_context.Subcategory, "ID", "Title", @event.SubcategoryID);
        return View(@event);
    }

    // POST: Events/Edit/5
    // To protect from overposting attacks, please enable the specific properties you want to bind to, for 
    // more details see http://go.microsoft.com/fwlink/?LinkId=317598.
    [HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> Edit(int id, [Bind("ID,Title,Description,Date,SubcategoryID,PlaceID,OrganisatorID")] Event @event)
    {
        if (id != @event.ID)
        {
            return NotFound();
        }

        if (ModelState.IsValid)
        {
            try
            {
                _context.Update(@event);
                await _context.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!EventExists(@event.ID))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }
            return RedirectToAction(nameof(Index));
        }
        ViewData["OrganisatorID"] = new SelectList(_context.Organisator, "ID", "Title", @event.OrganisatorID);
        ViewData["PlaceID"] = new SelectList(_context.Place, "ID", "Address", @event.PlaceID);
        ViewData["SubcategoryID"] = new SelectList(_context.Subcategory, "ID", "Title", @event.SubcategoryID);
        return View(@event);
    }

    // GET: Events/Delete/5
    public async Task<IActionResult> Delete(int? id)
    {
        if (id == null)
        {
            return NotFound();
        }

        var @event = await _context.Event
            .Include(@ => @.Organisator)
            .Include(@ => @.Place)
            .Include(@ => @.Subcategory)
            .SingleOrDefaultAsync(m => m.ID == id);
        if (@event == null)
        {
            return NotFound();
        }

        return View(@event);
    }

    // POST: Events/Delete/5
    [HttpPost, ActionName("Delete")]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> DeleteConfirmed(int id)
    {
        var @event = await _context.Event.SingleOrDefaultAsync(m => m.ID == id);
        _context.Event.Remove(@event);
        await _context.SaveChangesAsync();
        return RedirectToAction(nameof(Index));
    }

    private bool EventExists(int id)
    {
        return _context.Event.Any(e => e.ID == id);
    }
}

每个@=>@.Place 抛出2个错误： CS0119 'Place' 是一种类型，在给定的上下文 EventsPortal 中无效 CS1646 逐字说明符后应有关键字、标识符或字符串：@

一切都在一个上下文中

Answer 1

在 C# 中，@ 是逐字说明符，与多行字符串表达式一起使用以忽略转义字符和换行符。

只需用一些有效的标识符替换它，即 lambda 表达式中的“x”、“a”，它应该可以工作。

这里是Multiline String Literal in C# 使用@ 的示例。