实体框架核心2.0.1渴望在所有嵌套相关实体上加载 [英] Entity Framework Core 2.0.1 Eager Loading on all nested related entities
问题描述
我有一个简单的问题，但似乎无法解决。我正在使用Entity Framework Core 2.0.1版，并且希望默认加载我的所有实体。
I have a simple problem, but cant seem to find a way around it. I am using Entity Framework Core version 2.0.1 and want to eager load all my entities by default.
示例：
public class Order
{
public int Id { get; set; }
public string Name { get; set; }
public int CustomerId { get; set; }
public Customer Customer { get; set; }
}
public class Customer
{
public int Id { get; set; }
public string Name { get; set; }
public int AddressId { get; set; }
public Address Address { get; set; }
}
public class Address
{
public int Id { get; set; }
public string PostCode { get; set; }
public string City { get; set; }
}
但是当我加载 Order 实体时，实体客户，然后在其中地址为空
But when I load Order entity the related entity Customer and then inside it Address is null
我尝试过的操作：
- 尝试升级到2.1版并使用LazyLoadingProxies设置为false
只是一个例子，我有多个嵌套级别的实体，并且想在通用存储库中加载嵌套的相关数据，所以不能像我一样使用 Include 和 ThenInclude
This is just an example, I have entities with multiple nested levels and I want to load nested related data inside of a Generic Repository, so can't use Include and ThenInclude as I don't know the actual entity type when loading it.
示例：
public virtual async Task<IEnumerable<T>> GetAllAsync(Expression<Func<T, bool>> predicate = null)
{
if (predicate == null)
{
return await Context.Set<T>().ToListAsync();
}
return await Context.Set<T>().Where(predicate).ToListAsync();
}
我想念什么？我在存储库中有什么问题吗？
What am I missing? Is there something wrong I am doing in the repository? Any help or pointer towards a better design (if that's what the issue is here) are appreciated.
谢谢
推荐答案
该功能目前正式不存在（EF Core 2.0.2以及即将推出的2.1）。 急切加载所有导航属性＃4851 （已关闭），目前已对其进行了跟踪通过基于规则的紧急加载（包括）＃2953 和允许在模型中声明聚合（例如，定义包含的属性或通过其他方式）＃1985 （均在Backlog中，即没有具体的时间表）。
Such feature officially does not exist currently (EF Core 2.0.2 and also the incoming 2.1). It's been requested in Eager load all navigation properties #4851(Closed) and currently is tracked by Rule-based eager load (include) #2953 and Allow for declaring aggregates in the model (e.g. defining included properties or by some other means) #1985 (both in Backlog, i.e. no concrete schedule).
我可以提供以下两种自定义扩展方法：
I can offer the following two custom extension methods:
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.EntityFrameworkCore.Metadata;
namespace Microsoft.EntityFrameworkCore
{
public static partial class CustomExtensions
{
public static IQueryable<T> Include<T>(this IQueryable<T> source, IEnumerable<string> navigationPropertyPaths)
where T : class
{
return navigationPropertyPaths.Aggregate(source, (query, path) => query.Include(path));
}
public static IEnumerable<string> GetIncludePaths(this DbContext context, Type clrEntityType, int maxDepth = int.MaxValue)
{
if (maxDepth < 0) throw new ArgumentOutOfRangeException(nameof(maxDepth));
var entityType = context.Model.FindEntityType(clrEntityType);
var includedNavigations = new HashSet<INavigation>();
var stack = new Stack<IEnumerator<INavigation>>();
while (true)
{
var entityNavigations = new List<INavigation>();
if (stack.Count <= maxDepth)
{
foreach (var navigation in entityType.GetNavigations())
{
if (includedNavigations.Add(navigation))
entityNavigations.Add(navigation);
}
}
if (entityNavigations.Count == 0)
{
if (stack.Count > 0)
yield return string.Join(".", stack.Reverse().Select(e => e.Current.Name));
}
else
{
foreach (var navigation in entityNavigations)
{
var inverseNavigation = navigation.FindInverse();
if (inverseNavigation != null)
includedNavigations.Add(inverseNavigation);
}
stack.Push(entityNavigations.GetEnumerator());
}
while (stack.Count > 0 && !stack.Peek().MoveNext())
stack.Pop();
if (stack.Count == 0) break;
entityType = stack.Peek().Current.GetTargetType();
}
}
}
}
第一种只是应用多个字符串基础 Include 的便捷方法。
The first is just a convenient way of applying multiple string base Include.
第二种是实际收集所有<$ c $的工作使用EF Core提供的元数据为类型的c> include 路径。从传递的实体类型开始，它基本上是有向循环图处理，不包括所包含路径的逆向导航，而仅发出指向叶子路径的路径。
The second does the actual job of collecting all Include paths for a type using EF Core provided metadata. It's basically directed cyclic graph processing starting with the passed entity type, excluding the inverse navigations of the included paths and emitting only the paths to "leaf" nodes.
示例中的用法如下：
public virtual async Task<IEnumerable<T>> GetAllAsync(Expression<Func<T, bool>> predicate = null)
{
var query = Context.Set<T>()
.Include(Context.GetIncludePaths(typeof(T));
if (predicate != null)
query = query.Where(predicate);
return await query.ToListAsync();
}
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