配置关系时出现错误“字符串”不包含“订单”的定义并且没有可访问的扩展方法...”

Question

我正在尝试在我的两个实体Order和Item之间配置一对多关系。 但是，我收到以下错误：

错误CS1061'string'不包含'Orders'的定义，并且找不到接受'string'类型的第一个参数的可访问扩展方法'Orders'（您是否缺少using指令或程序集引用？ )

下面是我的 DbContext 的代码：

using Microsoft.EntityFrameworkCore;
using OrderEase.Models;

namespace OrderEase.Data
{
    public class OrderDbContext:DbContext
    {
        public OrderDbContext(DbContextOptions<OrderDbContext> options) : base(options)
        {

        }

        //Configure Relationships
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Order>().HasOne(o => o.Item).WithMany(i => i.Orders).HasForeignKey(o => o.ItemID);

            base.OnModelCreating(modelBuilder);
        }
    }
}

在下面的 Item 类中添加了导航属性：

using System.ComponentModel.DataAnnotations;



namespace OrderEase.Models
{
    public class Item
    {
        [Key]
        public int ItemID { get; set; }

        [Required(ErrorMessage = "Item name is required")]
        [Display(Name = "Item Name")]
        public string ItemName { get; set; }

        [Required(ErrorMessage = "Item price is required")]
        [DataType(DataType.Currency)]
        [Display(Name = "Price")]
        public decimal Price { get; set; }

        [Required(ErrorMessage = "Quantity in stock is required")]
        [Range(0, int.MaxValue, ErrorMessage = "Quantity must be non-negative")]
        public int QuantityInStock { get; set; }

        //One-to-Many Relationship with Order

        public int OrderID { get; set; } //Foreign Key referecing Order
        public ICollection<Order> Orders { get; set; }


    }
}

这是我的订单模型：

using Microsoft.EntityFrameworkCore.Metadata.Internal;

使用OrderEase.Data； 使用 System.ComponentModel.DataAnnotations；

命名空间 OrderEase.Models { 公开课订单 { [钥匙] 公共整数？订单ID { 获取;放; }

    [Required]
    public string  Item { get; set; }

    [Range(1, int.MaxValue, ErrorMessage = "Quantity must be greater than 0.")]
    public int Quantity { get; set; }

    [Required]
    [DataType(DataType.Currency)]
    public decimal TotalPrice { get; set; }

    [Required]
    [DataType(DataType.Date)]
    [Display(Name = "Order Date")]
    public DateTime OrderDate { get; set; }

    [Required]
    [DataType(DataType.Date)]
    [Display(Name = "Delivery Date")]
    public DateTime DeliveryDate { get; set; }

    [Required]
    public string Supplier { get; set; }
    public OrderStatus OrderStatus { get; set; }

    //Relationship 
    public List<Item> Items { get; set; }

}

}

如果我做错了，请多多指教。 我也检查了我的名字空间。一切看起来都很好。

Answer 1

我给你一个例子：

public class Order
{
    //...Other properties
    
    public string  Item { get; set; } //Remove this line
    public List<Item> Items { get; set; } //Remove this line
    public ICollection<Item> Items { get; set; } //Add this row to your Order model
}

public class Item
{
    //...Other properties
    
    public int OrderId { get; set; } //Add this line
    public virtual Order Order { get; set; } //Add this line
    public ICollection<Order> Orders { get; set; } //Remove this line
}

在创建模型时，像这样更改代码：

namespace OrderEase.Data
{
    public class OrderDbContext:DbContext
    {
        public OrderDbContext(DbContextOptions<OrderDbContext> options) : base(options)
        {

        }

        //Configure Relationships
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Order>()
            .HasMany(ur => ur.Items)
            .WithOne(u => u.Order)
            .HasForeignKey(ur => ur.OrderId)
            .IsRequired();

            base.OnModelCreating(modelBuilder);
        }
    }
}