C# EF检查集合初始化状态
让我们假设以下类别:C# EF检查集合初始化状态,c#,entity-framework,collections,lazy-loading,proxy-classes,C#,Entity Framework,Collections,Lazy Loading,Proxy Classes,让我们假设以下类别: public class Author { public virtual string Name { get; set; } public virtual List<Book> Books { get; set; } } public class Book { public virtual string Name { get; set; } public virtual Author Author { get; set; }
public class Author
{
public virtual string Name { get; set; }
public virtual List<Book> Books { get; set; }
}
public class Book
{
public virtual string Name { get; set; }
public virtual Author Author { get; set; }
}
public class Controller
{
public void DeleteBook(Book book)
{
var author = book.Author; //first check if it is loaded, not to invoke lazy loading?
author.Books.Remove(book) //check if the books collection is loaded?
book.Author = null;
Context.Set<Book>().Remove(book);
}
}
公共类作者
{
公共虚拟字符串名称{get;set;}
公共虚拟列表书{get;set;}
}
公共课堂用书
{
公共虚拟字符串名称{get;set;}
公共虚拟作者{get;set;}
}
公共类控制器
{
公共图书
{
var author=book.author;//首先检查它是否已加载,而不是调用延迟加载?
author.Books.Remove(book)//检查图书集合是否已加载?
book.Author=null;
Context.Set().Remove(book);
}
}
我的问题是-EF中是否有方法检查两种“已加载”状态?
我希望确保不会仅为了解除关联而加载图书作者和图书集合
我想写一些像:
public class Controller
{
public void DeleteBook(Book book)
{
if (EF.IsLoaded(book.Author)) //has it been (lazy) loaded / initialized?
{
if (EF.IsLoaded(book.Author.Books) //has it been (lazy) loaded / initialized?
{
book.Author.Books.Remove(book);
}
book.Author = null;
}
Context.Set<Book>().Remove(book);
}
}
公共类控制器
{
公共图书
{
if(EF.IsLoaded(book.Author))//是否已(惰性)加载/初始化?
{
if(EF.IsLoaded(book.Author.Books)//是否已(惰性)加载/初始化?
{
book.Author.Books.Remove(book);
}
book.Author=null;
}
Context.Set().Remove(book);
}
}
这可能吗?我知道您可以使用
RelationshipManager
检查集合是否已加载,它将与包含关系的任何实体一起工作,并实现ientitywhithrelations
var result = ((IEntityWithRelationships)(author)).RelationshipManager
.GetRelatedCollection<Books>("FK_Authors_Books", "Books");
if (result.IsLoaded == false)
{
// do something here
}
在DBContext中,您可以检查加载的对象是否访问属性Local,例如:DBContext.Book.Local 我想你可以这样做
public IsLoaded(Book book)
{
DBContext.Book.Local.Count(b => b.ID == book.ID) > 0;
}
请记住,我不是EF专家,但它可能会给您一个想法。DbContext.Entry方法使您能够访问DbContext中有关实体的所有信息。据我所知,您想知道传递的对象(作为参数)是否已经在内存中 还请记住,下面的方法正在使用 对于集合类型的导航属性,只需使用.Collection而不是.Reference
出于兴趣,解除关联是什么意思?在上下文中加载或不加载相关对象的事实不会更改关联。DbContext.Entry调用DetectChanges可能需要一段时间(秒或更长)。请确保在调用它之前禁用AutoDetectChangesEnabled。
public IsLoaded(Book book)
{
DBContext.Book.Local.Count(b => b.ID == book.ID) > 0;
}
public class Controller
{
public void DeleteBook(Book book)
{
// assuming that you're working on context directly and need to dispose it
using (var context = new YourContext())
{
var entry = context.Entry(book);
// Will tell you if Author navigation property is loaded
bool isLoaded = entry.Reference(x => x.Author).IsLoaded();
if (isLoaded != false)
{
// do when Author navigation property is loaded
}
else
{
// do when Author navigation property is not loaded
}
}
}
}