EF 6 Fluent Configuration - 具有父级的递归嵌套对象 - TPH

Question

我有以下实体，它有一个自身的集合和一个父属性，如果它是根小部件，我希望它为空：

public class CanvasWidgetQuery
{
    public int CanvasWidgetId { get; set; }

    public int? ParentCanvasWidgetId { get; set; }
    public virtual CanvasWidgetQuery ParentCanvasWidget { get; set; }
    public virtual ICollection<CanvasWidgetQuery> InnerCanvasWidgets { get; set; }

}

因为CanvasWidgetQuery 实际上只是一个基类（也可以是抽象的，但在我看到它在没有它的情况下工作之前我不会放抽象）。我想创建一个通用映射配置来映射CanvasWidgetQuery的派生类型：

public class CanvasWidgetQueryMap<TCanvasWidgetQuery> : EntityTypeConfiguration<TCanvasWidgetQuery>
    where TCanvasWidgetQuery : CanvasWidgetQuery
{
    public CanvasWidgetQueryMap() 
    {
        this.HasKey(q => q.CanvasWidgetId);

        this.HasMany(w => w.InnerCanvasWidgets)
            .WithOptional(w => w.ParentCanvasWidget)
            .HasForeignKey(w => w.ParentCanvasWidgetId);

    }
}

不管派生类型如何，它们都有这些属性，但不幸的是它抱怨WithOptional 调用（一次出现2个错误）：

 Error  1   Cannot implicitly convert type 'CanvasWidgetQuery' to 'TCanvasWidgetQuery'. An explicit conversion exists (are you missing a cast?) 


 Error  2   Cannot convert lambda expression to delegate type 'System.Func<CanvasWidgetQuery,TCanvasWidgetQuery>' because some of the return types in the block are not implicitly convertible to the delegate return type  

如果我将其提升到实际派生类型的映射：

 public class SearchCanvasWidgetQueryMap : CanvasWidgetQueryMap<SearchCanvasWidgetQuery>
{
    public SearchCanvasWidgetQueryMap() 
    {
        this.HasMany(w => w.InnerCanvasWidgets)
            .WithOptional(w => w.ParentCanvasWidget)
            .HasForeignKey(w => w.ParentCanvasWidgetId);
    }
}

现在它抱怨它不能同时将CanvasWidgetQuery 隐式转换为SearchCanvasWidgetQuery：

public class SearchCanvasWidgetQuery : CanvasWidgetQuery
{

}

我怎样才能完成我所追求的目标

Answer 1

您是否尝试为包含定义层次结构的属性的基类定义映射？

例如：

public class CanvasWidgetQueryMap<CanvasWidgetQuery> : EntityTypeConfiguration<CanvasWidgetQuery>
{
    public CanvasWidgetQueryMap() 
    {
        this.HasKey(q => q.CanvasWidgetId);

        this.HasMany(w => w.InnerCanvasWidgets)
            .WithOptional(w => w.ParentCanvasWidget)
            .HasForeignKey(w => w.ParentCanvasWidgetId);

    }
}

这里的答案中有一些很好的附加信息：CTP 4 doesn't consider base class properties 如果上述内容无法实现您的目标，这可能会有所帮助。