无法添加实体类型“ActivityEntity”的种子实体，因为没有为所需属性“SubjectId”提供值

Question

我正在为学校创建一个 .NET 应用程序，但我遇到了这个奇怪的内部错误。

The seed entity for entity type 'ActivityEntity' cannot be added because no value was provided for the required property 'SubjectId'

这是

ActivityEntity

课程：

public record ActivityEntity : IEntity
{
    public required DateTime StartDateTime { get; set; }
    public required DateTime EndDateTime { get; set; }
    public required Room Room { get; set; }
    public required ActivityType Type { get; set; }
    public string? Description { get; set; }

    public required SubjectEntity Subject { get; init; }
    public ICollection<EvaluationEntity> Evaluations { get; init; } = new List<EvaluationEntity>();
    
    public required Guid Id { get; set; }
}

这是

SubjectEntity

：

public record SubjectEntity : IEntity
{
    public required string Name { get; set; }
    public required string Abbreviation { get; set; }

    public ICollection<ActivityEntity> Activities { get; init; } = new List<ActivityEntity>();
    public ICollection<StudentEntity> Students { get; init; } = new List<StudentEntity>();
    
    public required Guid Id { get; set; }
}

这是失败的测试：

public async Task AddNew_Activity_Persisted()
    {
        //Arrange
        var entity = ActivitySeeds.ActivityEntity1;

        //Act
        SISDbContextSUT.Activities.Add(entity);
        await SISDbContextSUT.SaveChangesAsync();

        //Assert
        await using var dbx = await DbContextFactory.CreateDbContextAsync();
        var actualEntities = await dbx.Activities.SingleAsync(i => i.Id == entity.Id);
        Assert.Equal(entity, actualEntities);
    }

这是代码失败的部分：

public async Task InitializeAsync()
    {
        await SISDbContextSUT.Database.EnsureDeletedAsync();
        await SISDbContextSUT.Database.EnsureCreatedAsync();
    }

我创建了一个新的

DbContext

，.NET 似乎无法链接数据库？

这是数据库架构：

仅活动和主题相关。

这就是定义关系的方式：

modelBuilder.Entity<StudentEntity>()
            .HasMany(i => i.Subjects)
            .WithMany(i => i.Students);

        modelBuilder.Entity<ActivityEntity>()
            .HasOne(i => i.Subject)
            .WithMany(i => i.Activities);

        modelBuilder.Entity<EvaluationEntity>()
            .HasOne(i => i.Activity)
            .WithMany(i => i.Evaluations);

        modelBuilder.Entity<EvaluationEntity>()
            .HasOne(i => i.Student)
            .WithMany(i => i.Evaluations);

Answer 1

您与

1 - n

和

ActivityEntity

之间存在

SubjectEntity

关系。因此

SubjectId

中将会有一个隐式的

ActivityEntity

作为外键。所以我建议将这个隐式外键显式添加为属性。

public record ActivityEntity : IEntity
{
    public required DateTime StartDateTime { get; set; }
    public required DateTime EndDateTime { get; set; }
    public required Room Room { get; set; }
    public required ActivityType Type { get; set; }
    public string? Description { get; set; }

    public required SubjectEntity Subject { get; init; }
    
    // Add FK explicit
    public Guid SubjectId { get; init; }
    
    public ICollection<EvaluationEntity> Evaluations { get; init; } = new List<EvaluationEntity>();
    public required Guid Id { get; set; }
}

现在您可以在

SubjectId

中明确设置

ActivityEntity

进行播种。