EF Core配置同实体双向关联中间表时迁移报错求助

问题场景 #

使用EF Core构建漫画相关数据表，需创建两个关联Manga实体的中间表：

• MangaRelation：记录漫画间关联关系（续作、共享角色等）
• MangaRecommendation：记录漫画推荐关系

实体类定义 #

MangaRelation #

public class MangaRelation : BaseEntity
{
    public int ParentId { get; set; }
    public int ChildId { get; set; }

    public virtual Manga? Parent { get; set; }
    public virtual Manga? Child { get; set; }

    public RelationType RelationType { get; set; }
    public string? Description { get; set; }
}

MangaRecommendation #

public class MangaRecommendation : BaseEntity
{
    public int MangaId { get; set; }
    public int RecommendedMangaId { get; set; }
    public virtual Manga? Manga { get; set; }
    public virtual Manga? RecommendedManga { get; set; }
    public string? Reason { get; set; }
}

Manga #

public partial class Manga : BaseEntity
{
    public int MangaId { get; set; }
    public virtual ICollection<MangaRelation> Relations { get; set; } = new HashSet<MangaRelation>();
    public virtual ICollection<MangaRecommendation> Recommendations { get; set; } = new HashSet<MangaRecommendation>();
}

DbContext 配置代码 #

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);

    RegisterDbFunctions(modelBuilder);
    modelBuilder.Entity<Manga>(e =>
    {
        e.HasKey(p => p.MangaId);
        e.HasMany(p => p.RelationShips).WithOne(m => m.Parent).OnDelete(DeleteBehavior.Cascade);
        e.HasMany(p => p.Recommendations).WithOne(m => m.Manga).OnDelete(DeleteBehavior.Cascade);
    });       

    modelBuilder.Entity<MangaRelation>(e =>
    {
        e.HasKey(k => new { k.MangaParentId, k.MangaChildId });
        e.HasIndex(p => p.MangaParentId);
        e.HasIndex(p => p.MangaChildId);
        e.Property(p => p.MangaParentId);
        e.Property(p => p.MangaChildId);
        e.HasOne(p => p.Parent).WithMany().HasForeignKey(k => k.MangaParentId).HasConstraintName("FK_Manga_Parent")
            .OnDelete(DeleteBehavior.NoAction);
        e.HasOne(p => p.Child).WithMany().HasForeignKey(k => k.MangaChildId).HasConstraintName("FK_Manga_Child")
            .OnDelete(DeleteBehavior.NoAction);
        e.Property(p => p.RelationType).HasConversion<int>();
        e.Property(p => p.Description);
    });

    modelBuilder.Entity<MangaRecommondation>(e =>
    {
        e.HasKey(k => new { k.MangaId, k.RecommendedMangaId });
        e.HasIndex(p => p.MangaId);
        e.HasIndex(p => p.RecommendedMangaId);
        e.Property(p => p.Reason);
        e.Property(p => p.MangaId);
        e.HasOne(p => p.Manga).WithMany().HasForeignKey(k => k.MangaId).HasConstraintName("FK_MangaParent_Rec")
            .OnDelete(DeleteBehavior.NoAction);
        e.HasOne(p => p.RecommendedManga).WithMany().HasForeignKey(k => k.RecommendedMangaId)
            .HasConstraintName("FK_MangaRecParent_Rec").OnDelete(DeleteBehavior.NoAction);
        e.Property(p => p.RecommendedMangaId);
    });
}

报错信息 #

启用Nullable Context后，执行EF Core迁移命令时抛出以下错误：

System.InvalidOperationException: Cannot scaffold C# literals of type 'System.Reflection.NullabilityInfoContext'. The provider should implement CoreTypeMapping.GenerateCodeLiteral to support using it at design time.
   at Microsoft.EntityFrameworkCore.Design.Internal.CSharpHelper.UnknownLiteral(Object value)
   at Microsoft.EntityFrameworkCore.Design.Internal.CSharpHelper.<Fragment>g__AppendMethodCall|52_0(IMethodCallCodeFragment current, <>c__DisplayClass52_0&)
   at Microsoft.EntityFrameworkCore.Design.Internal.CSharpHelper.Fragment(IMethodCallCodeFragment fragment, Int32 indent)
   at Microsoft.EntityFrameworkCore.Migrations.Design.CSharpSnapshotGenerator.GenerateAnnotations(String builderName, IAnnotatable annotatable, IndentedStringBuilder stringBuilder, Dictionary`2 annotations, Boolean inChainedCall, Boolean leadingNewline)
   at Microsoft.EntityFrameworkCore.Migrations.Design.CSharpSnapshotGenerator.Generate(String modelBuilderName, IModel model, IndentedStringBuilder stringBuilder)
   at Microsoft.EntityFrameworkCore.Migrations.Design.CSharpMigrationsGenerator.GenerateMetadata(String migrationNamespace, Type contextType, String migrationName, String migrationId, IModel targetModel)
   at Microsoft.EntityFrameworkCore.Migrations.Design.MigrationsScaffolder.ScaffoldMigration(String migrationName, String rootNamespace, String subNamespace, String language)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.AddMigration(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigrationImpl(String name, String outputDir, String contextType, String namespace)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.AddMigration.<>c__DisplayClass0_0.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)
Cannot scaffold C# literals of type 'System.Reflection.NullabilityInfoContext'. The provider should implement CoreTypeMapping.GenerateCodeLiteral to support using it at design time.

解决方案 #

1. 修正实体与配置的字段/名称不匹配问题 #

代码中存在多处不一致，这是引发关系配置错误的核心原因：

• MangaRelation实体定义的是ParentId/ChildId，但配置中使用MangaParentId/MangaChildId，需统一字段名（要么修改实体，要么修改配置）
• Manga实体的集合属性是Relations，但配置中写的是p.RelationShips，需修正为p.Relations
• 配置中写错实体名：MangaRecommondation应为MangaRecommendation

修正后的核心配置片段：

// Manga实体配置修正
modelBuilder.Entity<Manga>(e =>
{
    e.HasKey(p => p.MangaId);
    e.HasMany(p => p.Relations).WithOne(m => m.Parent).OnDelete(DeleteBehavior.Cascade);
    e.HasMany(p => p.Recommendations).WithOne(m => m.Manga).OnDelete(DeleteBehavior.Cascade);
});

// MangaRecommendation实体配置修正
modelBuilder.Entity<MangaRecommendation>(e =>
{
    e.HasKey(k => new { k.MangaId, k.RecommendedMangaId });
    e.HasIndex(p => p.MangaId);
    e.HasIndex(p => p.RecommendedMangaId);
    e.Property(p => p.Reason);
    e.HasOne(p => p.Manga).WithMany(m => m.Recommendations).HasForeignKey(k => k.MangaId)
        .HasConstraintName("FK_MangaParent_Rec").OnDelete(DeleteBehavior.NoAction);
    e.HasOne(p => p.RecommendedManga).WithMany().HasForeignKey(k => k.RecommendedMangaId)
        .HasConstraintName("FK_MangaRecParent_Rec").OnDelete(DeleteBehavior.NoAction);
});

2. 处理Nullable Context相关bug #

如果字段修正后仍报错，尝试以下操作：

• 升级EF Core版本至6.0.7及以上，旧版本在Nullable Context下存在设计时生成的bug
• 临时关闭项目Nullable Context（修改项目文件中的<Nullable>enable</Nullable>为<Nullable>disable</Nullable>），生成迁移后再重新开启
• 检查BaseEntity的配置，避免将NullabilityInfoContext相关内容注入到模型注解中

3. 清理迁移缓存 #

执行以下命令清理设计时缓存，再重新生成迁移：

dotnet ef migrations remove
dotnet clean
dotnet restore
dotnet ef migrations add InitialCreate

内容的提问来源于stack exchange，提问作者Pascal Klose