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WPF & EF 4 Tales From the Trenches. Introductions Nathan Allen-Wagner Senior.NET Architect Bennett Adelson Consulting

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Presentation on theme: "WPF & EF 4 Tales From the Trenches. Introductions Nathan Allen-Wagner Senior.NET Architect Bennett Adelson Consulting"— Presentation transcript:

1 WPF & EF 4 Tales From the Trenches

2 Introductions Nathan Allen-Wagner Senior.NET Architect Bennett Adelson Consulting

3 Introductions Me - Online Blog Podcast Twitter@nathanaw

4 Agenda Quick Intro Entity Framework Models, Repositories, and T4 Templates Demos WPF Tips, Tricks, and Approaches Undo / Redo Demos

5 Session Goal… If I Succeed Today… 1.We’ll cover a lot of topics 2.I’ll convince you to download and explore the demo app. 3.I’ll introduce you to a couple open-source libraries

6 Quick Intro – High Level Entity Framework 1.Self Tracking Entities 2.Repositories a.Enabling Change Tracking b.Saving Changes 3.Customized template a.Partial Classes / Methods b.Delayed Initialization c.Undo WPF / MVVM 1.INotifyPropertyChanged 2.Undo / Redo 3.MVVM & Locators 4.Keyboard Focus 5.Reactive Programming 6.Threading

7 Quick Intro – Relevant Scenarios How does this apply to ME? Entity FrameworkUndoMVVM WPF YYY WinForms YYN Silverlight Y * Y Web YNN

8 Preview – The Demo App Demo! Before we dive in… … Here’s our demo app

9 PART 2 – WPF PART 1 Entity Framework

10 Definition of Terms: Models Models Are… …the “M” in MVC, MVP, MVVM Model View Controller Model View Presenter Model View ViewModel …the Data …the “Single Source of Truth” …Behavioral (methods)

11 Definition of Terms – Repositories Repositories are… …a way to get a model …a way to save changes to a model Persistence Ignorance… …hides data storage / access choices RDO, ADO, ADO.NET Nhibernate, EF, Linq2SQL …separates concerns …makes unit testing easier

12 Entity Framework – Model Designer & Code Generator Entity Framework: Model Designer -Database First -Model First Code Generator (T4 Templates) -Default Template -Self Tracking Entities Template -Plain Old CLR Objects (POCO) Template

13 Entity Framework – Self Tracking Entities Self Tracking Entities… Originally designed to enable EF over WCF 1)Share entity dll with client 2)Client entities track their changes 3)Changes sent back to service 4)Service applies changes to context But… works great for the Desktop too!

14 Entity Framework – Build your own Repository Goals for a Repository: 1)Use interfaces for definition 2)Expose methods to get, save and query 3)Keep all EF “stuff” inside. a.Clients should not need a reference to System.Data.Entities

15 Entity Framework – Repository Demo Demo – EF Basics EF Model Getting and Applying the STE template Separating entities into separate project Interfaces for repository Multiple Repositories: SQL & XML

16 Entity Framework – Repository Tips Demo – EF Tips & Tricks Loading Children From the DB .Include(“”) vs. LoadProperty(o => o.Child) Saving  ApplyChanges(), SaveChanges()  MarkAllAddedAsUnmodified(), RefreshAll()  AcceptAllChanges(), StartTrackingAll() Deletes  Parent.Remove() does not delete the record…

17 Entity Framework – Template Tips Demo – T4 Customizations Partial Classes / Methods  Partial Classes = Custom Logic / Properties  Partial Methods = Hooks into property changes Undo Hooks  T4 includes calls to UndoService for property changes OnInitializing() & OnInitialized()  Works with DelayedInitializationScope

18 Entity Framework – Delayed Initialization Scope Demo - Delayed Init Scope Entities call RegisterForEndInit() … Then EndInit() called after last scope completes Use in a using block Supports nesting ThreadStatic variables to track “current” Callers can check whether a scope is active

19 Entity Framework – Undo / Redo Tracking Demo – Undo / Redo Tracking Each setter tells Undo framework about change  SelfTrackingEntityUndoService.OnChanging() Undo framework adds a “change” to the undo stack Each “change” knows how to apply the previous value More on this later


21 WPF – Agenda Revisited WPF / MVVM 1.INotifyPropertyChanged 2.Undo / Redo 3.MVVM & Locators 4.Keyboard Focus 5.Reactive Programming 6.Threading

22 WPF – App Goals Goals for the Demo App Good Architecture… … Community says MVVM for WPF / SL. “Single Source of Truth” rendered in one or more views, which stay in sync as data changes in the model. Model contains core data and behavior. View-specific concerns are in the ViewModel or View. Undo / Redo support

23 WPF – Bindings and INotifyPropertyChanged WPF Bindings & INotifyPropertyChanged WPF means Powerful Binding Support! Two-Way bindings require Change Notification WPF UI elements use DependencyProperties for change notification. What about the model…???

24 WPF – Bindings and INotifyPropertyChanged Model Change Notification: System.ComponentModel.INotifyPropertyChanged Primary way to tell WPF that a property value changed System.Collections.ObjectModel.ObservableCollection Primary way to tell WPF that a collection changed Implements INotifyCollectionChanged Raises an event whenever items added, removed, replaced or relocated.

25 WPF – Using an Entity Framework Model Using a Model – Self Tracking Entities Partial Methods Revisited  Raising PropertyChanged for “dependent” properties  Validating data Undo / Redo Support  Importance of INPC for Undo – It changes the model  Available from  Hooking it up – Commands  Optimizations – Undo Batches

26 WPF – Dealing with ViewModels Dealing With ViewModels “Completing the INPC loop”  Snippets for Implementing INPC –On My Blog ( My Blog (  Remember to raise PropertyChanged for “dependent” properties  Crazy Cool: ContinuousLinq’s ReactiveObject –

27 WPF – Tips and Tricks WPF Tips and Tricks Keyboard Focus  Toolbars don’t cause “LostFocus” event  Use the CommitBindingsBehavior to force bindings.  Demo…

28 WPF – Tips and Tricks WPF Tips and Tricks Design Time & “Blendability”  Use “design-time” detection to populate ViewModels.  Demo…

29 WPF – Tips and Tricks WPF Tips and Tricks Threading  Use the BackgroundWorker for lengthy operations  Marshal all changes back to UI thread via: –Dispatcher.Invoke() / BeginInvoke() –SynchronizationContext.Send() / Post()  Warning! Collections are problematic. Some solutions exist, but each has problematic edge cases.  T4 Template includes SynchronizedContextCollection, which attempts to marshall changes to UI via SynchronizationContext.

30 WPF – Weak References & Weak Events FYI: Weak References & Weak Events WPF uses these extensively Critical to allowing the GC to collect memory Important when you have GC roots holding on to things (like static instances). May need a memory profiler. Event Handlers create a reverse reference. If you don’t disconnect, it might lock things in memory.

31 WPF – ViewModel Locators ViewModel Locator Options Code-behind / Resource MVVM Light – Smart Resource Caliburn – ViewModel-First (awesome framework!) MEFed MVVM – Using MEF to create ViewModels My Preference: Converter Based Locators Demo (if time permits)

32 Thanks! Congratulations! We made it to… The End! (If you’d like more info one of these topics, let us know)

33 Thanks! Thanks! See you next month! (Please turn in evals) Nathan Allen-Wagner.NET Architect - Bennett Adelson Blog Podcast Twitter@nathanaw

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