We can stop creation of proxy in the context constructor by using
this.Configuration.ProxyCreationEnabled = false;
What are the advantages and disadvantages of creating proxies in EF 4.1 ?
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2 Answers
Proxies are necessary for two features:
- Lazy loading - navigation properties are loaded once accessed first time
- Dynamic change tracking - if you modify any property in the entity the context is notified about this change and set the state of the entity. If dynamic change tracking is not used, context must use snapshot change tracking which means discovery all changes before saving takes place = exploring all properties even if they were not changed.
Both these techniques have other requirements:
- Lazy loading - all navigation properties in the entity must be
virtual. Lazy loading must be enabled. - Dynamic change tracking - all mapped properties must be
virtual.
3 Comments
yigitt
Hi, I have a question if you could help? ChangeTracker tracks any entity that is attached to the context. So if I change any property of an entity it is marked as modified. So this means it is being tracked anyway without virtual keyword . What is the need of setting scalar properties virtual as they are already being tracked by context.But it is said that scalar properties are marked virtual for change tracking. What change tracking affect virtual keyword has on scalar properties other than I mentioned?
Bob Sammers
@UfukSURMEN There are different types of change tracking at play, which Ladislav mentions in his answer.
Virtual properties enable dynamic tracking, which notices every time a property is altered. WIthout the virtual keyword, snapshot tracking is used which compares the values of every property with their previous values on DetectChanges(). Which one you should use is a nuanced question.yigitt
@BobSammers thanks for reply,and pretty good article about this subject.
In addition to Previous answer, Runtime use your POCO class using reflection and create a Dynamic Proxy class inheriting your POCO class. So it will add those functionalities + EntityObject functionalities in runtime that will help Dynamic proxies to enable Lazy Loading and Dynamic change Tracking.
