时间戳

首页 > 解决方案 > Ef core Odata 多对多

c# - Ef core Odata 多对多

问题描述

我正在使用 ODATA 开发 Asp .Net Core 2.2 应用程序。我有测试应用程序来重现该问题：我无法通过 ODATA 请求请求带有链接表的链接实体。

请求：/odata/Books?$expand=BookCategories

响应错误：

"Message": "The query specified in the URI is not valid. Property 'BookCategories' on type 'GameStorageView.Data.Book' is not a navigation property or complex property. Only navigation properties can be expanded.",
"ExceptionMessage": "Property 'BookCategories' on type 'GameStorageView.Data.Book' is not a navigation property or complex property. Only navigation properties can be expanded.",
"ExceptionType": "Microsoft.OData.ODataException",

模型：

 public class Book
    {
        public int BookId { get; set; }
        public string Title { get; set; }
        public ICollection<BookCategory> BookCategories { get; set; }
    }

    public class Category
    {
        public int CategoryId { get; set; }
        public string CategoryName { get; set; }
        public ICollection<BookCategory> BookCategories { get; set; }
    }

    public class BookCategory
    {
        public int BookId { get; set; }
        public Book Book { get; set; }
        public int CategoryId { get; set; }
        public Category Category { get; set; }
    }

模型创建：

modelBuilder.Entity<BookCategory>()
                .HasKey(bc => new {bc.BookId, bc.CategoryId});
            modelBuilder.Entity<BookCategory>()
                .HasOne(bc => bc.Book)
                .WithMany(b => b.BookCategories)
                .HasForeignKey(bc => bc.BookId);
            modelBuilder.Entity<BookCategory>()
                .HasOne(bc => bc.Category)
                .WithMany(c => c.BookCategories)
                .HasForeignKey(bc => bc.CategoryId);

如何让它发挥作用？如何通过 odata 请求多对多实体？

升级版：

ODATA 配置： .EntityType.Count().Filter().OrderBy().Expand(SelectExpandType.Allowed,10).Select().Page().Count();

linq 查询工作正常： context.Book.Include(c=>c.BookCategories).ToArray()

标签： c#asp.net.netentity-framework-coreodata

解决方案

好的，我的解决方案不是最好的，但它有效：我们需要为其添加字段ID和唯一约束：

public class BookCategory
    {
        public int Id { get; set; }
        public int BookId { get; set; }
        public Book Book { get; set; }
        public int CategoryId { get; set; }
        public Category Category { get; set; }
    }

和

modelBuilder.Entity<BookCategory>().HasAlternateKey(bc => bc.Id);

然后如果我们想通过 odata 加载链接实体，我们还需要将链接实体添加到 odata 路由。我使用扩展方法，所以它看起来像这样：

public static void RegisterOdataRoute<TEntity>(this ODataConventionModelBuilder builder, string name = null, bool pluralize = true) where TEntity : class
        {
            name = name ?? $"{typeof(TEntity).Name}";

            var names = pluralize ? $"{name}s" : name;

            OdataRoutes.Add(name, $"~/odata/{names}");
            builder.EntitySet<TEntity>(names).EntityType.Count().Filter().OrderBy().Expand(SelectExpandType.Allowed,10).Select().Page().Count();
        }
    }

和

app.UseOData(builder =>
            {
                builder.RegisterOdataRoute<BookCategory>();
                    ...

如果有人找到更好的解决方案，请告诉我！

推荐阅读