This document discusses using interfaces and dependency injection to create a clean repository pattern with Entity Framework. It presents a typical dependency structure and issues with directly referencing data access layers. The solution shown uses interfaces to abstract data access and dependency injection to decouple layers. Code examples demonstrate implementing repositories, domain logic with constructor injection, and controllers without data dependencies. Benefits include flexibility to change data layers and performance.

1. A Clean Repository Pattern In EF
Via Interfaces
By Brandon D’Imperio
Imaginarydevelopment.blogspot.com

2. What’s wrong?
Typical dependency structure

3. What’s wrong?
We want to move to Azure
Typical dependency structure
We want to add a thick client against ADO for
our existing web to Azure.

4. What’s wrong?
We want to move to Azure
Typical dependency structure Persistence change = somewhere
between massive rework to lots of code
adjustments
We want to add a thick client against ADO for
our existing web to Azure.
UI against multiple data layers=
somewhere between massive rework and
lots of searching for dependencies

5. We need something more adaptable
• We want to be able to swap out these layers
with ease, or even on the fly.

6. What about this?
Dependency-free foundation

7. How?
• EF layer
– Entities implement shared interfaces
– Context implements IRepository<T>
– T4 for automation
– Query Interception
• EF does not allow nor handle IQueryable<T> where T:
(parent to an Entity)

8. Code Break

9. The Visitors are here

10. Sample Query in EF context

11. Performance
left join and where

12. Performance Code

13. Performance
select and where id> i take(50)
Straight EF average: 103.811ms
Intercepted average: 220.3158ms

14. More Performance
Straight EF Average=1190.3ms
Intercepted Average=1274.43 ms

15. Domain Layer - How?
• Constructor Injection
• Depends ONLY on the shared interfaces (and
sometimes DTOs)
• No state, only behavior

16. Domain Code

17. Domain Code – public sample

18. Domain Code – public sample

19. Domain – Data Layer check-mate
SELECT
[Extent2].[ID] AS [ID],
[Extent2].[DealID] AS [DealID],
[Extent2].[ScenarioNumber] AS [ScenarioNumber],
[Extent2].[ServiceCodeID] AS [ServiceCodeID],
[Extent2].[CountryCode] AS [CountryCode],
[Extent2].[CurrencyCode] AS [CurrencyCode],
[Extent2].[PriceListID] AS [PriceListID],
[Extent2].[BranchID] AS [BranchID],
[Extent2].[ExchangeRate] AS [ExchangeRate],
[Extent2].[Volume] AS [Volume],
[Extent2].[ActualPrice] AS [ActualPrice],
[Extent2].[CurrentPrice] AS [CurrentPrice],
[Extent2].[StandardPrice] AS [StandardPrice],
[Extent2].[MinVol] AS [MinVol],
[Extent2].[MaxVol] AS [MaxVol],
FROM [Treasury].[Deal] AS [Extent1]
INNER JOIN [Treasury].[DealActivity] AS [Extent2] ON [Extent1].[DealID] = [Extent2].[DealID]
WHERE [Extent1].[RegionID] IN (5,1,6,4,2)

20. UI layer - How?
• Controller requires appropriate Model(s)
• No dependencies on the data layer

21. UI layer – controller code

22. Create - post

23. Delete and Edit

24. Edit - post

25. View sample
Create + Edit

26. Edit scripts

27. Technologies utilized
• Mvc3 – Now open source! -
http://aspnet.codeplex.com/
• T4 -
http://en.wikipedia.org/wiki/Text_Template_Tran
– T4Mvc - https://t4mvc.codeplex.com/
• Ninject – http://ninject.org
• jQuery - http://jquery.com/
• IQToolkit - http://iqtoolkit.codeplex.com/

28. References
• Orm speed comparison -
http://code.google.com/p/dapper-dot-net/
• Open Stackoverflow question -
http://stackoverflow.com/questions/9422789/can
• Dependency Injection in .net by Mark
Seemann - http://manning.com/seemann

29. Available Sidebar or presentations
• Static Reflection
• A maybe monad in .net
– http://maybe.codeplex.com
• Unit Testing
– Asp.net Routing
• T4
– DTO generation
• Hybrid Winforms/Mvc application
– Hybrid winforms+mvc pages
• Mvc 3/4
– Inline templates
– Custom templates
• XNA
– http://PitofDespair.codeplex.com