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Building an enterprise app in silverlight 4 and NHibernate
- 1. Building an enterprise application with Silverlight and NHibernateGill CleerenMicrosoft Regional Director/MVP ASP.NETVisugUsergroup lead - Ordinawww.snowball.beBart WullemsMCT, MCPDApplication Architect Ordinabartwullems.blogspot.com
- 2. AgendaBuilding the foundationCQRSODataNHibernateBuilding the front-end in SilverlightMVVMWhat is MVVM?Why and why notThe parts of MVVMImplementing MVVM principlesDemoFinding your VM using MEFCommandingCommunication between VMs
- 3. Scenario: Planning your vacation with NHibernate and Silverlight
- 7. CQS DefinedBertrand Meyer (via Wikipedia)“Command Query Separation”“every method should either be a command that performs an action, or a query that returns data to the caller, but not both. In other words, asking a question should not change the answer.”
- 8. CQRS definedMeyer: Separate command methods that change state from query methods that read state.Greg Young: Separate command messages that change state from query messages that read state.Can have significant architectural implications
- 9. Welcome CQRS
- 10. QueriesSimple Query LayerSimple views or sprocs or selects from denormalized tablesSimple DTOs, no mapping neededDon’t go through the Domain Model, as it pollutes itViewModel per query perhapsWhy should the data come across 5 layers through 3 model transformations to populate a screen? (Udi)Synchronous, no messaging needed
- 11. CommandsCommands capture intent, DTOs don’tCustomerDTOvsCustomerChangedAddressCommandHandler per commandCan be validated outside of domain entitiesThis is why domain entities are never invalid, commands that would produce invalid state are rejected
- 12. CommandsSeparate Data ModificationMake preferredChange addressA generic DTO could do these things, of course, but after the fact, how do you know what actually happened?UI ImplicationsGrid-like screens don’t workCommands require specific intent
- 13. How do we implementthis?
- 14. Implement the query model usingodata
- 15. OData.org
- 16. A RESTful Interface for DataJust HTTPData as resources, HTTP methods to act on itLeverage caching, proxies, authentication, …Uniform URL syntaxEvery piece of information is addressablePredictable and flexible URL syntaxMultiple representationsUse regular HTTP content-type negotiationAtomPub, JSON
- 17. Model and Operation SemanticsUnderlying data modelEntity Data ModelEntities ResourcesAssociationsLinksOperation semanticsMapping of HTTP methodsGET Retrieve resourcePOST Create resourcePUT Update resourceDELETE Delete resource
- 18. WCF (Data) ServicesWCF Data Services WCF ServicesRESTAtomPubODataSOAPWS-SecurityWS-*
- 19. WCF Data ServicesHTTPData Services RuntimeReflection Provider.NET Classes [+ LINQ provider]Data Source(IQueryable)
- 20. oData and SilverlightAccessing Data ServicesSilverlight ClientHttp stack still an optionData Services Client more usable as it knows the details of the data service interfaceFeaturesFull abstraction on top of the service – no need to deal with HTTP, serialization, etcData as objects with automatic change trackingLINQ for queriesData-binding friendly interfacesWork same-domain and cross-domain
- 22. DemoUsingOData to implement the query part of CQRS22
- 23. Implement the domain model usingnhibernate
- 24. NHibernateFull-featured ORM solutionOpen sourceBased on Java’s Hibernate frameworkUses XML(by default) to map tables/columns to objects/properties
- 25. NHibernate API
- 26. NHibernateQuickstartCreate hibernate.cfg.xml or use app.configvarcfg = newConfiguration(); cfg.Configure();varsf = cfg.BuildSessionFactory();using(var s = sf.OpenSession())using(vartx = s.BeginTransaction()) { var c = s.Get<Customer>(42);tx.Commit();}
- 27. WhyNHibernate?EntityFrameworkGreatforRapidApplicationDevelopmentFalls short forEnterpriseApplicationDevelopmentNHibernate has More maturityMore flexibilityBetterextensibility
- 30. Convention over ConfigurationFluentNHibernatehttp://fluentnhibernate.orgReplacesXML mappingbyfluentmappingXML configurationbyfluentconfigurationAdvantagesType safetyRemovestedious XML mappingsIntuitive interfaceConventions
- 31. AutomaticSession managementDataContext per RequestIServiceBusRequest 1Session 1DBSession 2Request 2
- 32. DemoUsing NHibernate to implement the domain part of CQRS32
- 33. Building the front-end in Silverlight
- 34. What is MVVM?
- 35. Understanding MVVMMVVM :is an architectural pattern created by John Gossman from WPF teamis a variation of MVC patternis similar to Martin Fowler’s PresentationModel patternworks because of Silverlight data Binding & commandingis typically used in WPF/SL-applications to leverage the power of XAML, so that Devs and Designers can work together easier35
- 37. Why and why not MVVM?
- 38. Why MVVMBetter SoC (Seperation of Concerns)More maintainableModel never needs to be changed to support changes to the viewViewModel rarely needs to be changed to support changes to the viewMore testable ViewModelis easier to unit test than code-behind or event driven codeEliminates the need to do code behind which leaves the UI all in XAML 38
- 39. Why MVVMBecause the framework (SL & WPF) have the power to support itDatabinding/DataContextIncreases the "Blendability" of your view
- 40. Why not MVVMLack of standardization so everyone has own favorMessage to community is not clear!!For simple UI, M-V-VM can be overkill
- 41. Too much code neededINotifyPropertyChangedCommands40
- 42. The parts of MVVM
- 43. What we all do…All UI code in code-behindViewXAMLData ModelCode-BehindEvent Handlers
- 44. The MVVM wayViewXAMLCode-BehindChange notificationData-binding and commandsView ModelData ModelState + Operations
- 45. The parts of MVVMView knows ViewModel
- 47. But not vice versa.ViewViewModelModel44
- 48. The ViewThe viewrepresents the user interface that the user will see.can be a user control or Data Templateshouldn't contain any logic that you want to testshould be kept as simple as possible.45
- 49. The ViewModelAn abstraction of View
- 50. Connector between View and Model
- 51. Make VM as testable as possible46
- 52. The ModelCan be Data Model, DTO, POCO, auto-generated proxy of domain class and UI Model based on how you want to have the separation between Domain Service and Presentation Layer
- 53. No reference to ViewModel47
- 54. Where to start?BING (or google is fine as well )MVVM Light ToolkitPrismCaliburn48
- 55. DemoLet’s take a look at an MVVM implementation49
- 57. View model base classImplements INotifyPropertyChangedContains base code for all VMs to re-use51
- 59. Which comes first...2 options: View firstViewModel first53
- 60. ViewFirstBased on XAML mostlyThe View has a relationship to its ViewModel (usually through data binding).DataContext={Binding ...}Available at design time (Blend support)54View<UserControl.DataContext> <dive:PageViewModel /></UserControl.DataContext>
- 61. ViewModel FirstThe ViewModel creates the view usually through an IoCcontaineror MEF 55View Modelpublic MyViewModel(IMyViewmyView){myView.Model = this;}
- 62. How to implement this?Locator patternImplemented through a class that contains all VMs as static propertiesAn instance is then made available as ResourceAll Views can bind, no code needed in View Clean way Not good since all VMs need to be known upfrontProperty for each available VMDifficult if application is MDI-like (more than one instance available)56
- 63. DemoLocator57
- 64. How to implement this?MEFBased on Import: class says it needs an instance of a specific typeExport: class says it wants to be made available for compositionComposition: MEF links imports and exports togetherCan create one shared instance or dynamic number thereofSolves earlier problemEasy for testing and mocking58
- 65. DemoMEF59
- 66. CommandingInstead of having event handlers in code-behind, we use commandsSL4 has the ICommand interfaceExecute methodCanExecutepropertyCanExecuteChangedeventWay to create commands:Write ICommand implementationCreate instance on VMBind Command property of control to this instance60
- 67. CommandingCommanding is supported on ButtonBase Button, HyperlinkButtonNot on others like ComboBox SelectionChangedCan be solved with event triggers Can be added on every eventPart of System.Windows.InteractivityCan be bound to every control
- 68. DemoCommanding62
- 69. Communication 63View ModelView ModelView ModelView ModelView ModelView ModelView ModelView Model
- 70. Communication64ViewViewXAMLXAMLCode-BehindCode-BehindView ModelData ModelView ModelState + OperationsData ModelState + OperationsMessagePublish messagesViewXAMLCode-BehindSubscribe to messagesEvent AggregatorView ModelMessageState + Operations
- 71. CommunicationVM’s need to be able to talk to each other, eg: send messages to each otherNot a good idea to have each VM reference all other VMsSolution:Event Aggregator/mediator/messengerVM can register to receive messages of a certain type (for example string messages)Another VM can register with the same messenger to send messagesThis allows both VMs to communicate with each other without tight coupling65
- 73. Some tips to take homeUse MVVM in Blend
- 74. In View’s constructor, check DesignerProperties.IsInDesignToolUnit testingVMs can easily be unit-testedSilverlight Unit Testing Framework ships with Silverlight 4Can be used from the browserNo real way to integrate with automated testing (MSBuild) yet67
- 76. SummaryCQRS Gives the necessary level of scalability and maintainabilityforenterpriseapplicationsoData is greatfor the query partNHibernate rocks for the command partMVVMCreate better testable applicationsWorks for both Silverlight and WPF
- 77. Questions?
Editor's Notes
- #2: Gill
- #3: Gill
- #4: Gill
- #6: TraditionalN-tierleavestoomuchquestionsunansweredHow to handle the gap betweenvisualization and domain specification(how do youchangeyourrich domain model intosomethingthatcanbevisualized) Most business logicgotscatheredaround
- #23: Ons query model tonen(is ook opgebouwd met nHibernate)DataServiceKey attribuutTravelPlannerQueryContextTravelPlannerQueryServiceDataServiceKey even aanpassen naar CityNameAantal voorbeeld urls tonen:/Cities/Cities(‘Paris’)/Cities(‘Paris’)/CityNameCities(‘Paris’)/name/$value/$metadataLinqPad tonen voor complexe gevallen