asp.net core中的多对多crud操作

Question

我有两个实体(Product和Supply)，它们具有多对多关系。在这两个ID之间还有一个实体(SupplyProduct)。

我的实体:

public class Product
{
[Key]
public int ProductId { get; set; }
[Required]
public string? ProductName { get; set; }
[Required]
[Column(TypeName = "decimal(6,2)")]
public decimal UnitPrice { get; set; }
public int Quantity { get; set; }
public string? Brand { get; set; }
public DateTime CreatedDateTime { get; set; } = DateTime.Now;
//Many to many relationship between the products and the stocks
public virtual ICollection<SupplyProduct>? SupplyProducts { get; set; }
}
public class Supply
{
[Key]
[Required]
public int SupplyId { get; set; }
[Required]
[DisplayName("Supply's Label")]
public string? Label { get; set; }

//One to many relationship between the Stock and the Merchant
public Merchant? Merchant { get; set; }
//Many to many relationship between the stocks and the products
public virtual ICollection<SupplyProduct>? SupplyProducts { get; set; }
}
public class SupplyProduct
{
[Key]
public int SupplyId { get; set; }
public virtual Supply? Supply { get; set; }
[Key]
public int ProductId { get; set; }
public virtual Product? Product { get; set; }
}

我想在创建产品时为其分配供应。然后显示供应及其相关产品

这是我的产品控制器:

ProductsController.cs

public class ProductController : Controller
{
private readonly ApplicationDbContext _db;
public ProductController(ApplicationDbContext db)
{
_db = db;
}
// GET: ProductController
public ActionResult Index()
{
IEnumerable<Product> ProductsList = _db.Products;
return View(ProductsList);
}
// GET: ProductController/Create
public ActionResult Create()
{
IEnumerable<Supply> SuppliesList = _db.Supplies.Include(s => s.Merchant);
ViewBag.Supplies = SuppliesList;
return View();
}
// POST: ProductController/Create
[HttpPost]
public ActionResult Create(Product model, List<int> supplyIds)
{
_db.Products.Add(model);
_db.SaveChanges();

SupplyProduct SP = new();
foreach (var supplyId in supplyIds)
{
SP.SupplyId = supplyId;
SP.ProductId = model.ProductId;
SP.Product = model;
SP.Supply = _db.Supplies.Where(x => x.SupplyId == supplyId).FirstOrDefault();
}
_db.SupplyProducts.Add(SP);
_db.SaveChanges();
return RedirectToAction(nameof(Index));
}
}

你能检查一下我的帖子吗Create方法是否正常，以及如何在将Index方法中的Supplies返回到索引视图时获得Products数据?

非常感谢你的帮助和快乐的编码:D

Answer 1

你能检查一下我的帖子创建方法，如果它应该是

像下面这样修改你的代码，否则你将总是在supplyIds中存储第二个供应:

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Create(Product model, List<int> supplyIds)
{
_context.Product.Add(model);
_context.SaveChanges();
SupplyProduct SP = new();
foreach (var supplyId in supplyIds)
{
SP.SupplyId = supplyId;
SP.ProductId = model.ProductId;
SP.Product = model;
SP.Supply = _context.Supply.Where(x => x.SupplyId == supplyId).FirstOrDefault();
_context.SupplyProducts.Add(SP);   //move to here...
_context.SaveChanges();
}
// _context.SupplyProducts.Add(SP);
//_context.SaveChanges();
return RedirectToAction(nameof(Index));
}

如何获得Products数据，同时将Index方法中的Supplies返回到索引视图中?

像下面这样改变你的Index方法:

// GET: Products
public async Task<IActionResult> Index()
{
var data = await _context.Product.Include(p => p.SupplyProducts)
.ThenInclude(sp => sp.Supply).ToListAsync();
return View(data);
}

Answer 2

如果除了SupplyProduct之外没有任何其他属性，您可以删除SupplyProduct表，因为您不需要它用于多对多。然后在Supply和Product

中初始化集合

public class Product
{
public Product()
{
this.Supplys = new HashSet<Supply>();
}
//... your props
public virtual ICollection<Supply> Supplys { get; set; }
}
public class Supply
{
public Supply()
{
this.Products = new HashSet<Product>();
}
//... your props
public virtual ICollection<Product> Products { get; set; }
}

仅用一个查询添加产品到供应(在您的代码中，您对supplyIds中的每个Id进行查询)

[HttpPost]
public ActionResult Create(Product model, List<int> supplyIds)
{
//Get all supplys you need by id
var supplys = _db.Supplys
.Where(x => supplyIds.Contains(x.SupplyId))
.ToList();

//Add product in each supply
foreach (var supply in supplys)
{
supply.Products.Add(model);
}
//Update db
_db.SaveChanges();
return RedirectToAction(nameof(Index));
}

Get from DB

public ActionResult GetSuplys(List<int> supplyIds)
{
//Here you get all Supplys with the Products in it
var supplys = _db.Supplys
.Include(x => x.Products)
.Where(x => supplyIds.Contains(x.SupplyId))
.ToList();
//...
}

节省新产品供应

public ActionResult NewSuply()
{
var supply = new Supply
{
ProductName = name,
//Add all props you need
//You can add Product here or add empty collection
Products.Add(product), or = new List<Product>();
}

//No need to save Product separate
_db.Add(supply);
_db.SaveChanges();
}