Question

我开始使用ASP.NET MVC Core进行编码，我想为库系统中的Checkout书籍创建一个新模型。我创建了一个名为CheckoutModel的新子文件夹，在其中我创建了CheckoutModel.cs 当我运行应用程序时，它给我发了一个告诉我的错误：

无法隐式转换类型＆＃39; LibaryData.Models.Checkout＆＃39;至＆＃39; LibaryManagmentSystems.Models.Checkout.CheckoutModel＆＃39;

我尝试重命名类名并更改子文件夹名称和模型名称，但同样问题。

CatalogController.cs

using LibaryData;
using LibaryManagmentSystems.Models.Catalog;
using LibaryManagmentSystems.Models.Checkout;
using Microsoft.AspNetCore.Mvc;
using System.Linq;
using LibaryData.Models;

namespace LibaryManagmentSystems.Controllers
{
    public class CatalogController : Controller
    {
        private ILibaryAsset _assets;
        private ICheckout _checkouts;

        public CatalogController(ILibaryAsset assets, ICheckout checkout)
        {
            _assets = assets;
            _checkouts = checkout;
        }

        public IActionResult Index()
        {
            var assetModels = _assets.GetAll();

            var listingResult = assetModels
                .Select(result => new AssetIndexListingModel
                {
                    Id =result.Id,
                    ImageUrl = result.ImageUrl,
                    AuthorOrDirector = _assets.GetAuthorOrDirector(result.Id),
                    DeweyCallNumber = _assets.GetDeweyIndex(result.Id),
                    Title = result.Title,
                    Type = _assets.GetType(result.Id)
                });
            var model = new AssetIndexModel()
            {
                Assets = listingResult
            };
            return View(model);
        }

        public IActionResult Detail(int id)
        {
            var asset = _assets.GetById(id);
            var currentHolds = _checkouts.GetCurrentHolds(id)
                .Select(a => new AssetHoldModel
                {
                    HoldPlace = _checkouts.GetCurrentHoldPlaced(a.Id).ToString("d"),
                    PatronName = _checkouts.GetCurrentHoldPatronName(a.Id)



                });


            var model = new AssetDetailModel
            {
                AssetID = id,
                Title = asset.Title,
                Type = _assets.GetType(id),
                Year = asset.Year,
                Cost = asset.Cost,
                Status = asset.Status.Name,
                ImageURL = asset.ImageUrl,
                AuthorOrDirector = _assets.GetAuthorOrDirector(id),
                CurrentLocation = _assets.GetCurrentLocation(id)?.Name,
                DeweyCallNumber = _assets.GetDeweyIndex(id),
                CheckoutHistory = _checkouts.GetCheckOutHistory(id),
                ISBN = _assets.GetIsbn(id),
                LatestChechout = _checkouts.GetLatesCheckout(id),
                PatronName = _checkouts.GetCurrentCheckoutPatron(id),
                CurrentHolds = currentHolds

            };
            return View(model);
        }

        public IActionResult Checkout(int id)
        {
            var asset = _assets.GetById(id);

            var model = new Models.Checkout.CheckoutModel
            {
                AssetId = id,
                ImageUrl = asset.ImageUrl,
                Title = asset.Title,
                LibaryCardId ="",
                isCheckOut = _checkouts.IsCheckedOut(id)
            };
            return View(model);
        }

        public IActionResult MarkLost(int assetID)
        {
            _checkouts.MarkLost(assetID);
            return RedirectToAction("Detail", new { id = assetID });
        }

        [HttpPost]
        public IActionResult PlaceCheckout(int assetID, int libaryCardId)
        {
            _checkouts.CheckInItem(assetID, libaryCardId);
            return RedirectToAction("Detail", new { id = assetID });
        }

        [HttpPost]
        public IActionResult PlaceHold(int assetID, int libaryCardId)
        {
            _checkouts.PlaceHold(assetID, libaryCardId);
            return RedirectToAction("Detail", new { id = assetID });
        }

        public IActionResult Hold(int id)
        {
            var asset = _assets.GetById(id);

            var model = new CheckoutModel
            {
                AssetId = id,
                ImageUrl = asset.ImageUrl,
                Title = asset.Title,
                LibaryCardId = "",
                isCheckOut = _checkouts.IsCheckedOut(id),
                HoldCount = _checkouts.GetCurrentHolds(id).Count()
            };
            return View(model);
        }
    }
}

Checkout.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel.DataAnnotations;

namespace LibaryData.Models
{
    public class Checkout
    {
        public int Id { get; set; }

        [Required]
        public LibaryAsset LibaryAsset { get; set; }
        public LibaryCard LibaryCard { get; set; }
        public DateTime Since { get; set; }
        public DateTime Until { get; set; }
    }
}

CheckoutModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace LibaryManagmentSystems.Models.Checkout
{
    public class CheckoutModel
    {
        public string LibaryCardId { get; set; }
        public string Title { get; set; }
        public int AssetId { get; set; }
        public string ImageUrl { get; set; }
        public int HoldCount { get; set; }
        public bool isCheckOut { get; set; }
    }
}

任何建议，有帮助吗？

它在CatalogController.cs中显示错误：

LatestChechout = _checkouts.GetLatesCheckout(id)

 public Checkout GetLatesCheckout(int assetId)
        {
            return _context.Checkouts
                .Where(c => c.LibaryAsset.Id == assetId)
                .OrderByDescending(c=>c.Since)
                .FirstOrDefault();

        }

AssetsDetailModel.cs

using LibaryData.Models;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using LibaryData.Models;
using System;

namespace LibaryManagmentSystems.Models.Catalog
{
    public class AssetDetailModel
    {

        public int AssetID { get; set; }
        public string Title { get; set; }
        public string AuthorOrDirector { get; set; }
        public string Type { get; set; }
        public int Year { get; set; }
        public string ISBN { get; set; }
        public string DeweyCallNumber { get; set; }
        public string  Status { get; set; }
        public decimal Cost { get; set; }
        public string CurrentLocation { get; set; }
        public string ImageURL { get; set; }
        public string PatronName { get; set; }
        public Checkout LatestCheckout { get; set; }
        public IEnumerable<CheckoutHistory> CheckoutHistory { get; set; }
        public IEnumerable<AssetHoldModel> CurrentHolds { get; set; }


    }

    public class AssetHoldModel
    {
        public string PatronName { get; set; }
        public string HoldPlace { get; set; }


    }
}

Answer 1

根据第二个错误（在评论中）＆＃34;数据类型＆＃39; Checkout＆＃39;是一个名称空间但是像LibaryManagmentSystems类型一样使用，代码在名为Checkout的类和名为Checkout的名称空间之间混淆，这些名称都可以从AssetDetailModel访问（由于类所在的命名空间以及文件中的using语句。

要解决此问题，您可以

1）更改您的类或命名空间，使它们不再具有相同的名称

或者

2）通过在属性声明中显式指定checkout类的完整命名空间来消除代码中的歧义：

public LibaryData.Models.Checkout LatestCheckout { get; set; }

这将清楚地表明它正是被引用的对象（而不是命名空间LibaryManagmentSystems.Models.Checkout）。

无法声明模型＆＃34;无法隐式转换类型＆＃34;

1 个答案: