c# - Entity Framework 6 Getter Only 属性影响实体关系

Question

我在 Entity Framework 如何推断实体关系方面遇到了概念障碍。因此，虽然我已经解决了我的问题，但我不明白为什么它会起作用。

我有以下实体，这里是简化形式，来自 Geometry Class Library .

行类，为简洁起见隐藏主键/外键属性并关注问题:

public class Line
{
    public virtual Point BasePoint
    {
        get { return _basePoint; }
        set { _basePoint = value; }
    }
    private Point _basePoint;

    public virtual Direction Direction
    {
        get { return _direction; }
        set { _direction = value; }
    }
    private Direction _direction;
}

Vector 类，Line 的子类，也隐藏了主/外键属性:

public class Vector : Line
{
    public virtual Distance Magnitude
    {
        get { return _magnitude; }
        set { _magnitude = value; }
    }
    private Distance _magnitude;

    public virtual Point EndPoint
    {
        get { return new Point(XComponent, YComponent, ZComponent) + BasePoint; }
    }
}

LineSegment 类，Vector 的子类，也隐藏了主/外键属性:

public partial class LineSegment : Vector
{
    public virtual Distance Length
    {
        get { return base.Magnitude; }
        set { base.Magnitude = value; }
    }

    public List<Point> EndPoints
    {
        get { return new List<Point>() { BasePoint, EndPoint }; }
    }
}

据我了解， Entity Framework 会忽略 getter-only 属性，仅映射具有 getter 和 setter 的属性。但是，为了避免出现错误

Unable to determine a valid ordering for dependent operations. Dependencies may exist due to foreign key constraints, model requirements, or store-generated values.

在将 LineSegment 插入数据库时​​(Line 和 Vector 工作正常)，我必须在我的模型创建中包含以下内容:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    // ...

    // Set up Line model
    modelBuilder.Entity<Line>()
        .HasKey(line => line.DatabaseId);
    modelBuilder.Entity<Line>()
        .HasRequired(line => line.BasePoint)
        .WithMany()
        .HasForeignKey(line => line.BasePoint_DatabaseId); // Identify foreign key field
    modelBuilder.Entity<Line>()
        .HasRequired(line => line.Direction)
        .WithMany()
        .HasForeignKey(line => line.Direction_DatabaseId); // Identify foreign key field

   modelBuilder.Entity<Vector>()
        .HasRequired(vector => vector.Magnitude)
        .WithMany()
        .HasForeignKey(vector => vector.Magnitude_DatabaseId); // Identify foreign key field

    modelBuilder.Entity<LineSegment>()
       .Ignore(lineSegment => lineSegment.Length);
    modelBuilder.Entity<LineSegment>() // Why this? EndPoints is a getter only property
       .Ignore(lineSegment => lineSegment.EndPoints);
}

其中大部分内容对我来说都有意义，但是为了让 Entity Framework 理解我的模型并且不产生上面引用的错误，为什么我必须包含最后一条语句？

Answer 1

Entity Framework 似乎自动忽略了字符串类型、基本类型和枚举类型的 getter-only 属性。在所有其他情况下，您必须使用 .Ignore() 方法或 [NotMapped] 注释显式忽略它们。