What is the difference between Lazy Loading and Lo

问题:

In Entity Framework 4, what is the difference between Lazy Loading, and using Load() method?

Edit: I have added, two 'if' statements:

Lazy Loading:

var query = from c in context.Contacts select c;
foreach ( var contact in query ) {
     if ( contact.ID == 5 )
        Console.WriteLine( contact.Addresses.City );
}

Load() method:

context.ContextOptions.LazyLoadingEnabled = false;

var query = from c in context.Contacts select c;
foreach ( var contact in query ) {
     if ( contact.ID == 5 ) {
        contact.Addresses.Load()
        Console.WriteLine( contact.Addresses.City );
     }
}

Now, having this two 'if' checks, why should I preffer one before another?

回答1:

Lazy Loading means that a load will only occur once the object is needed, thus not loading unnecessary data.

When you disable Lazy Loading you say that you will load yourself by calling load.

http://en.wikipedia.org/wiki/Lazy_loading

Lazy Loading is disabled by default, so when you set it to false in your first line it does not do anything.

When you call Load, you will load all the related objects to that database (which is not needed in this case which makes it work without it)

回答2:

This post on Working with Lazy Loading in EF 4 Code First should also help with understanding how Entity Framework behaves both with and without lazy loading enabled. It also demonstrates that it is enabled by default in EF4 and how to disable it on a per-instance or by default for your application basis.