Lazy and Eager Loading in Entity Framework gives same result while using .Include() in both?

Question

I have tried to implement lazy and eager loading in EF. Everything seems fine, but the .Include() method is available in both cases and returns the same results irrespective of lazy loading false or true.

I have 2 tables categories and product. Category can have multiple products and related using foreign key.

When I load categories using lazy loading by using .Include("Products"), it loads all products related to categories.

Same behavior is shown by eager loading.

var results = objDB.Categories.Include("Products").ToList(); // Enabled lazy load

var results = objDB.Categories.Include("Products").ToList(); // Disabled lazy load

Above both lines have same result. Please clarify this confusion.

.Include should not be available in case of lazy loading = true.

Please give your valuable opinion. Thanks in advance.

haim770 · Accepted Answer · 2015-12-27 07:11:04Z

3

When you're explicitly using Include(), you're preforming an Eager Loading. Obviously, disabling/enabling Lazy Loading has no effect.

The difference will be reflected when you'll omit the Include and try to access the Products navigation-property in some of your Category instances. When Lazy-Loading is enabled, EF will load it from the database. When it's disabled, you'll get null.

answered Dec 27, 2015 at 7:11

haim770

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Gurmeet Over a year ago

Okay @haim, Does it means that .Include() method will decide what loading we will use. If we used .include() in either case it wil load Eagerly and if we will not use .Include() only then it depends on LazyLoadingEnabed=True /False.

undefined · Accepted Answer · 2015-12-27 09:59:31Z

The difference will be that if you have lazy loading on any entities which are not loaded by the original query will be accessable transparently, and when accessed will trigger an additional query. For example

var results = objDB.Categories.Include("Products").ToList(); // Enabled lazy load
var thing = results.First().Products.First().AnotherEntity;//This will trigger another query and thing will get a value

var results = objDB.Categories.Include("Products").ToList(); // Disabled lazy load
var thing = results.First().Products.First().AnotherEntity;//Thing will be null as its not included in the original result set

FWIW I think most people using lazy loading are causing themselves problems. The only place I would use lazy loading is in a forms/wpf application where people are essentially browsing data in the database and you want to fetch more data as the user clicks things. I don't think there's ever a case for lazy loading in a web application, you are better to be explicit about the data you want from the DB.

Charles Owen · Accepted Answer · 2018-03-28 05:44:23Z

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Include and ToList are both considered eager methods, so you wouldn't be invoking lazy loading. It's only when you try to access the property of a related entity would the lazy loading feature kick in.

answered Mar 28, 2018 at 5:44

Charles Owen

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