c# - ASP.NET Core 2.2 在多对多插入时返回 "NotSupportedException: Collection was of a fixed size"

Question

当我尝试插入ASP 中的多对多 链接表时，出现“NotSupportedException: Collection was of a fixed size”。 NET 核心 2.2。 我可以在 SQL Server 中手动插入值!

我的实体是:

    public class Product
    {
        [key]
        public int Id {get;set;}

        public ICollection<ProductCategory> ProductCategories { get; set; } = new List<ProductCategory>();
    }

    public class Category
    {
        [key]
        public int Id {get;set;}

        public string Name { get; set; }

        public ICollection<ProductCategory> ProductCategories { get; set; } = new List<ProductCategory>();

    }

    public class ProductCategory
    {
        [Key]
        public int ProductId { get; set; }
        public Product Product { get; set; }

        [Key]
        public int CategoryId { get; set; }
        public Category Category { get; set; }
    }

在 DbContext 中:

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {

            modelBuilder.Entity<ProductCategory>().HasKey(t => new { t.ProductId, t.CategoryId });


            modelBuilder.Entity<ProductCategory>()
                .HasOne(bc => bc.Product)
                .WithMany(b => b.ProductCategories)
                .HasForeignKey(bc => bc.ProductId);

            modelBuilder.Entity<ProductCategory>()
                .HasOne(bc => bc.Category)
                .WithMany(c => c.ProductCategories)
                .HasForeignKey(bc => bc.CategoryId);

            base.OnModelCreating(modelBuilder);
        }

        public DbSet<Product> Products { get; set; }
        public DbSet<Category> Categories { get; set; }
        public DbSet<ProductCategory> ProductCategories {get; set;}

我尝试向 Product 和 Category 插入记录，插入的记录没有问题。 但是，当我尝试插入链接记录时，我得到了 "NotSupportedException: Collection was of a fixed size" 错误。

插入:

            var Electronics = new Category
            {
                Name = "Electronics",
            };

            var Exir = new Product
            {
                Name = "Exir",
            };

            var pc1 = new ProductCategory();

            bc1.Product = Exir ;
            bc1.Category = Electronics;
            Exir.ProductCategories.Add(pc1);

            sqlContext.Categories.Add(Electronics);
            sqlContext.Products.Add(Exir);
            sqlContext.SaveChanges();

Answer 1

当使用固定大小的数据结构(如空数组)初始化集合属性时，可能会发生此错误。