Lazy Loading

• It is the process that automatically loads the data of a navigation property from the database the first time that it is accessed.
• When using POCO entity types, lazy loading is achieved by creating instances of derived proxy types and then overriding virtual properties to add the loading hook.
• In the following example, Student class contains StudentAddress as a complex property.
• Context first loads all the students from the database, then it will load the address of a particular student when we access StudentAddress property.

db.Configuration.LazyLoadingEnabled = true;
var student = db.Students.First();
// Loads Student address for the current Student (Executes seperate SQL query).
var address = student.StudentAddress;

Rules for Lazy Loading

1. context.Configuration.ProxyCreationEnabled should be true.
2. context.Configuration.LazyLoadingEnabled should be true.
3. Complex property should be defined as virtual.
   • Context will not do lazy loading if the property is not define as virtual.

Turn lazy loading off for serialization

• Lazy loading and serialization don’t mix well, and if you aren’t careful you can end up querying for your entire database just because lazy loading is enabled.
• Most serializers work by accessing each property on an instance of a type.
• Property access triggers lazy loading, so more entities get serialized.
• On those entities properties are accessed, and even more entities are loaded. It’s a good practice to turn lazy loading off before you serialize an entity.

Turning off lazy loading for specific navigation properties

• Lazy loading of a collection can be turned off by making the property non-virtual.
• Loading of the collection can still be achieved using eager loading or the Load method.

Turn off lazy loading for all entities

• Lazy loading can be turned off for all entities in the context by setting a flag on the Configuration property.