Entity Framework 正在加载 Polygon
中的所有内容,但我的 LineSegments
列表。我错过了什么?
多边形:
public class Polygon
{
List<LineSegment> _lineSegments = new List<LineSegment>();
public List<LineSegment> LineSegments
{
get { return _lineSegments; }
protected set { _lineSegments = value; }
}
public Point BasePoint { get; protected set; }
public Vector NormalVector { get; protected set; }
public int? DatabaseId { get; set; }
// ...
}
LineSegment 类(
Polygon
有这些列表)public class LineSegment
{
public virtual Distance Magnitude
{
get { return _magnitude; }
set { _magnitude = value; }
}
private Distance _magnitude;
public virtual Point BasePoint
{
get { return _basePoint; }
set { this._basePoint = value; }
}
private Point _basePoint;
public virtual Direction Direction
{
get { return _direction; }
set { _direction = value; }
}
private Direction _direction;
public int? DatabaseId { get; set; }
// ...
}
这是模型中的关系设置:
modelBuilder.Entity<Polygon>()
.HasMany(polygon => polygon.LineSegments);
因此,多边形和线段都有一个表,它们正确插入到线段引用多边形的位置。但是当我尝试使用预先加载来检索它们时,它不会加载列表。我在包含中列出了 LineSegment 的属性,但它不起作用。我想我需要修改模型中的关系设置,但我不确定如何修改。 如何更正此问题,以便在加载多边形时立即加载 LineSegments 列表? 这是查询:
private static List<Expression<Func<Polygon, object>>> polygonRegionNaviationProperties = new List<Expression<Func<Polygon, object>>>()
{
(polygon => polygon.BasePoint),
(polygon => polygon.BasePoint.X),
(polygon => polygon.BasePoint.Y),
(polygon => polygon.BasePoint.Z),
(polygon => polygon.NormalVector),
(polygon => polygon.NormalVector.Direction),
(polygon => polygon.NormalVector.Direction.Phi),
(polygon => polygon.NormalVector.Direction.Theta),
(polygon => polygon.NormalVector.Magnitude),
(polygon => polygon.NormalVector.BasePoint.X),
(polygon => polygon.NormalVector.BasePoint.Y),
(polygon => polygon.NormalVector.BasePoint.Z),
(polygon => polygon.LineSegments),
(polygon => polygon.LineSegments.Select(lineSegment => lineSegment.Direction)),
(polygon => polygon.LineSegments.Select(lineSegment => lineSegment.Direction.Phi)),
(polygon => polygon.LineSegments.Select(lineSegment => lineSegment.Direction.Theta)),
(polygon => polygon.LineSegments.Select(lineSegment => lineSegment.Magnitude)),
(polygon => polygon.LineSegments.Select(lineSegment => lineSegment.BasePoint.X)),
(polygon => polygon.LineSegments.Select(lineSegment => lineSegment.BasePoint.Y)),
(polygon => polygon.LineSegments.Select(lineSegment => lineSegment.BasePoint.Z))
};
public Polygon GetPolygon(int? databaseId)
{
if(databaseId != null)
{
Polygon retrievedPolygon = Query((polygon => polygon.DatabaseId == databaseId), polygonRegionNaviationProperties);
return retrievedPolygon;
}
else
{
return null;
}
}
public override Polygon Query(Expression<Func<Polygon, bool>> match, List<Expression<Func<Polygon, object>>> includes = null)
{
using (var databaseContext = new ClearspanDatabaseContext())
{
databaseContext.Database.Log = Console.Write;
if (includes != null)
{
var dataSet = databaseContext.Set<Polygon>(); // Get the relevant DataSet
Polygon retrievedObject = includes.Aggregate( // Eagerly load the passed navigation properties
dataSet.AsQueryable(),
(current, include) => current.Include(include)
).SingleOrDefault(match);
databaseContext.Entry(retrievedObject).Collection(polygon => polygon.LineSegments).Load();
return retrievedObject;
}
else
{
Polygon retrievedObject = databaseContext.Set<Polygon>().SingleOrDefault(match);
databaseContext.Entry(retrievedObject).Collection(polygon => polygon.LineSegments).Load();
return retrievedObject;
}
}
}
更新
这是一个链接到一个细化的 project 说明我的问题。
git submodule init
和 git submodule update
)(如果你使用 SourceTree,这可能会自动发生) 希望这有助于理解、诊断和解决这个问题。您会注意到,在我的问题中,我简化了 GeometryClassLibrary 中实际存在的层次结构。谢谢,斯科特 H
最佳答案
这是 Polygon.LineSegments
的代码:
public virtual List<LineSegment> LineSegments
{
get { return this._Edges.Select(e => (LineSegment)e).ToList(); }
set { _Edges = value.ToList<IEdge>(); }
}
当 EF 填充子集合时,它不会为其分配一个完整的集合,而是在必要时对其进行初始化,然后向其中添加项目。现在这里是陷阱:EF 向哪个集合添加项目?不是
_Edges
,而是每次 ToList()
被寻址时由 LineSegments
构建的临时集合。 _Edges
本身仍然是空的。不幸的是,你不能通过
Include()
-ing Edges
而不是 LineSegments
来解决这个问题,因为这是 Edges
的代码:protected List<IEdge> _Edges = new List<IEdge>();
public virtual List<IEdge> Edges
{
get { return _Edges; }
set { _Edges = value; }
}
EF 不支持接口(interface)。坦率地说,我不知道是否有像样的解决方法。
LineSegments
中的这种间接性可能会导致 EF 出现更多问题。例如,我认为关系修复(从加载到上下文中的实体自动填充导航属性)也不会运行。我知道这些类来自外部库。我在那里看到所有这些
XyzEntityFramework
部分类(例如 LineSegmentEntityFramework
),它们似乎添加了属性以方便使用 EF。也许他们愿意查看您的问题并找到解决方案。关于.net - Eager Load 上的 Entity Framework 6 加载列表,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/32530093/