[英]EF: Loading related objects of related objects
我找不到从DB加载对象及其所有相关对象的方法。 关于这个简化的模型(ID-Properties未显示):
class MainClass
{
public virtual ICollection<FirstLevelClass> FirstLevelObjects {get; set;}
}
class FirstLevelClass
{
public virtual ICollection<SecondLevelClassA> SecondLevelObjectsA {get; set;}
public virtual ICollection<SecondLevelClassB> SecondLevelObjectsB {get; set;}
}
class SecondLevelClassA
{
public virtual int SomeValue {get; set;}
}
class SecondLevelClassB
{
public virtual int SomeValue {get; set;}
}
DbContext在“MainClass”上 - 对象:
public SampleContext : DbContext
{
public DbSet<MainClass> MainClassObjects {get; set;}
}
如何从db加载包含所有第一级和第二级对象的MainClass对象? 我可以:
using (var context = new SampleContext())
{
var MainClassObjects = context.MainClassObjects.Include(p => p.FirstLevelObjects).ToList();
// ...move objects from the context to program logic...
}
但是我如何获得SecondLevelObjects? 我错过了类似的东西:
using (var context = new SampleContext())
{
var MainClassObjects = context.MainClassObjects.Include(p => p.FirstLevelObjects.SecondLevelObjects).ToList();
// ...move objects from the context to program logic...
}
这甚至是可能的还是我必须在DbContext中调整DbSets?
一种解决方案可以是使用Include方法的其他重载,它采用如下字符串:
var MainClassObjects = context.MainClassObjects
.Include("FirstLevelObjects")
.Include("FirstLevelObjects.SecondLevelObjects")
.ToList();
更新:
当您使用此方法时,您只需确定要获取的路径,以便更新问题,您可以使用此方法:
var MainClassObjects = context.MainClassObjects
.Include("FirstLevelObjects.SecondLevelObjectsA")
.Include("FirstLevelObjects.SecondLevelObjectsB")
.ToList();
尝试这个:
using (var context = new SampleContext())
{
var MainClassObjects = context.MainClassObjects.Include(p => p.FirstLevelObjects.SelectMany(s => s.SecondLevelObjects)).ToList();
// ...move objects from the context to program logic...
}
您应该添加.Select()
语句来获取对象或列表。
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