如何在 Entity Framework Core 3 中无键播种数据？

Question

描述

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我想将数据播种到我的数据库中。数据没有键或 ID 值。但由于某种原因我收到了错误：

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System.NullReferenceException: Object reference not set to an instance of an object.\n   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.get_IsKeyUnknown()\n   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.PropagateToUnknownKey(EntityState oldState, EntityState entityState, Boolean adding, Nullable`1 forceStateWhenUnknownKey)\n   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityState entityState, Boolean acceptChanges, Boolean modifyProperties, Nullable`1 forceStateWhenUnknownKey)\n   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.Microsoft.EntityFrameworkCore.Update.IUpdateEntry.set_EntityState(EntityState value)\n   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.TrackData(IModel source, IModel target)\n   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.Diff(IModel source, IModel target, DiffContext diffContext)\n   at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationsModelDiffer.GetDifferences(IModel source, IModel target)\n   at Microsoft.EntityFrameworkCore.Migrations.Design.MigrationsScaffolder.ScaffoldMigration(String migrationName, String rootNamespace, String subNamespace, String language)\n   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType)\n   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType)\n   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()\n   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()\n   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)\nObject reference not set to an instance of an object.\n

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如果我尝试使用密钥添加示例数据，它会起作用。是否无法在没有 key/id 的情况下将示例数据添加到数据库中？

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代码

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模型构建器扩展.cs

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using Microsoft.EntityFrameworkCore;\nusing workbranch.Models.Db.Helper;\nusing workbranch.Models.HonorarTool;\n\nnamespace workbranch.Models.Db\n{\n    public static class ModelBuilderExtensions\n    {\n        public static void Seed(this ModelBuilder modelBuilder)\n        {\n            modelBuilder.Entity<HonorarToolLists>()\n                .HasNoKey()\n                .HasData(\n                    new HonorarToolLists\n                    {\n                        Name = "TGA-MT",\n                        Year = 2013,\n                        ChargeableCosts = 5000,\n                        Zone = 1,\n                        MinRate = 2132,\n                        MaxRate = 2547\n                    }\n                );\n        }\n    }\n}\n

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荣誉工具列表.cs

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using System.ComponentModel.DataAnnotations.Schema;\nusing System;\nusing System.Collections.Generic;\nusing System.ComponentModel.DataAnnotations;\nusing System.Linq;\nusing System.Threading.Tasks;\n\nnamespace workbranch.Models.HonorarTool\n{\n    public partial class HonorarToolLists\n    {\n        public string Name { get; set; }\n\n        public int Year { get; set; }\n\n        public int ChargeableCosts { get; set; }\n\n        public int Zone { get; set; }\n\n        public int MinRate { get; set; }\n\n        public int MaxRate { get; set; }\n    }\n}\n

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AppDbContext.cs

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using System.Net.Sockets;\nusing System.ComponentModel.DataAnnotations;\nusing System;\nusing System.Collections.Generic;\nusing System.Linq;\nusing System.Threading.Tasks;\nusing Microsoft.AspNetCore.Identity;\nusing Microsoft.AspNetCore.Identity.EntityFrameworkCore;\nusing Microsoft.AspNetCore.Mvc;\nusing Microsoft.EntityFrameworkCore;\nusing workbranch.Models.StatusReporting;\nusing workbranch.Models.HonorarTool;\n\nnamespace workbranch.Models.Db\n{\n    public class AppDbContext : IdentityDbContext\n    {\n        public AppDbContext(DbContextOptions<AppDbContext> options) : base(options)\n        { }\n        public DbSet<HonorarToolLists> HonorarToolLists { get; set; }\n\n        protected override void OnModelCreating(ModelBuilder builder)\n        {\n            base.OnModelCreating(builder);\n\n            builder.Seed();\n        }\n    }\n}\n

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