EF6不延迟加载导航属性 [英] EF6 does not lazy load navigation property

问题描述

我在与EF6延迟加载的问题。我搜索计算器，但我发现的其他问题不适合我的情况。

我使用了虚拟关键字和我的班公共。 LazyLoadingEnabled 和 ProxyCreationEnabled 均设置为真正。

当我打开一个当然对象， presentationId 被设置为正确的 ID 和演示是空这是正确的，因为它没有被加载。

当我通过演示属性设置为 PresentationsController.ToDto（）方法，它应该是懒加载状态，但我得到的方法在空引用例外，因为它仍然空。

我知道，关系工作，因为当我强迫加载演示在<$ C $一个当然在监视窗口以一个破发点的属性C>公共静态CourseDto ToDto（课程项目，DnbContext DB）方法，它被加载。见图片：

正如你所看到 item.presentation 是空：

当我手动评估 db.courses.Find（257）.presentation 这是引用相同的演示文稿作为项目对象呢，他们都装：

下面是我的波苏斯：

 公共抽象类BaseModel：ISoftDelete {
公众诠释ID {搞定;组; } 
} 
 
公共类课程：BaseModel {
 [必填] 
公众诠释presentationId {搞定;组; } 
公共虚拟介绍介绍{搞定;组; } 
} 
  

我的Web API控制器方法：

  //获取API /课程/ 5 
公共CourseDto GetCourse（INT ID）{
 VAR项目= db.courses.FirstOrDefault（X = > x.id == ID）; 
返回ToDto（项目，DB）; 
} 
 
公共静态CourseDto ToDto（课程项目，DnbContext DB）{
变种DTO =新CourseDto（）; 
 
如果（item.presentationId大于0）dto.presentation = PresentationsController.ToDto（item.presentation，DB）; 
 
返回DTO; 
} 
  

任何想法？

解决方案

实体必须明确宣布公共构造如果要通过动态代理使用延迟加载。 （如果您有其他带参数）

 公共抽象类BaseModel：ISoftDelete {
公共BaseModel（）{} 
酒店的公共INT编号{搞定;组; } 
} 
 
公共类课程：BaseModel {
公共课程（）{} 
 [必填] 
公众诠释presentationId {搞定;组; } 
公共虚拟介绍介绍{搞定;组; } 
} 
  

I'm having an issue with EF6 lazy loading. I've searched StackOverflow, but the other questions I've found doesn't fit my case.

I'm using the virtual keyword and my classes are public. LazyLoadingEnabled and ProxyCreationEnabled are both set to true.

When I load a course object from the db, presentationId is set to the correct id and presentation is null which is correct, because it hasn't been loaded yet.

When I pass the presentation property to the PresentationsController.ToDto() method it should be lazy loaded, but I get a null reference exception inside the method because it's still null.

I know that the relationships are working because when I force load the presentation property of a course in the Watch window with a break point at the public static CourseDto ToDto(Course item, DnbContext db) method it gets loaded. See images:

As you can see item.presentation is null:

When I manually evaluate db.courses.Find(257).presentation which is referencing the same presentation as the item object does, they're both loaded:

Here are my POCOs:

public abstract class BaseModel : ISoftDelete {
    public int id { get; set; }
}

public class Course : BaseModel {
    [Required]
    public int presentationId { get; set; }
    public virtual Presentation presentation { get; set; }
}

My Web API controller methods:

// GET api/Courses/5
public CourseDto GetCourse(int id) {
    var item = db.courses.FirstOrDefault(x => x.id == id);
    return ToDto(item, db);
}

public static CourseDto ToDto(Course item, DnbContext db) {
    var dto = new CourseDto();

    if (item.presentationId > 0) dto.presentation = PresentationsController.ToDto(item.presentation, db);

    return dto;
}

Any ideas?

解决方案

Entities must have explicitly declared public constructors if you want to use lazy loading via dynamic proxies. (If you have other with parameters)

public abstract class BaseModel : ISoftDelete {
    public BaseModel() { }
    public int id { get; set; }
}

public class Course : BaseModel {
    public Course() { }
    [Required]
    public int presentationId { get; set; }
    public virtual Presentation presentation { get; set; }
}

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