Stock Trader Reference Implementation Using the Prism Library 5.0 for WPF

From: Developer's Guide to Microsoft Prism Library 5.0 for WPF

Prism includes a sample called a reference implementation, which is a composite application that is based on a real-world scenario. This intentionally incomplete application illustrates the composite application baseline architecture. Within the application, you will see solutions for common, and recurrent, challenges that developers face when creating composite applications. We solve many of the challenges using design patterns such as Model-View-ViewModel (MVVM), Composite View, Event Aggregator, Plug-In, and Dependency Injection that embody important architectural design principles such as separation of concerns and loose coupling. Prism helps you to create a modular application design and build applications using loosely coupled components that can evolve independently but that can be easily and seamlessly integrated into the overall application.

The reference implementation is not a real-world application; however, it is based on real-world challenges customers are facing. When you look at this application, do not look at it as a reference point for building a stock trader application—instead, look at is as a reference for building a composite application.

Note: When looking at this application, it may seem inappropriate to implement it in the way it was implemented. For example, you might question why there are so many modules, and it may seem overly complex. The focus of Prism is to address challenges around building composite applications. For this reason, certain scenarios are used in the reference implementation to emphasize those challenges.

The following illustration shows the desktop version of the Stock Trader Reference Implementation (Stock Trader RI).

Stock Trader RI

You can use the reference implementation in different ways. You can step through a running example that demonstrates application-specific code built on reusable guidance. You can also copy sections of the source code that implement any particular guidance into your own applications.

The reference implementation was developed using a "test driven" approach and includes automated (unit) tests for most of its components. You can modify the reference implementation and use the unit tests to verify its functionality. The reference implementation for the Prism 5.0 release demonstrates several key features of the updated Prism library:

• Managed Extensibility Framework (MEF) as the dependency injection container
• Modularity and user interface (UI) composition through custom attributes
• Model-View-ViewModel pattern (MVVM)
• Region-based navigation

Building and Running the Reference Implementation

The Stock Trader RI requires Visual Studio 2012 or later and the .NET Framework 4.5.1. The reference implementation is compatible with Blend for Visual Studio 2013.

To run the Stock Trader RI In Windows Explorer, double-click the following shortcut file to open the solution in Visual Studio:

Open RI - StockTrader Reference Implementation.lnk

1. Press F5.

Interacting with the Reference Implementation

The features of the Stock Trader reference implementation are covered in greater detail later in the Scenarios section. The following steps provide a quick introduction to the basic features.

To see the pie chart and line chart for each stock

1. Click the Position tab.
2. In the Position table, click the row that corresponds to the stock whose pie chart and line chart you want to see.

To see a news item corresponding to a stock

1. Click the Position tab.
2. In the Position table, click a stock in that corresponds to the stock you want to learn more about.
3. Click a news article. If you click the control in the upper-right corner, a News Reader dialog box opens.

To add a stock to the watch list

1. In the Add to Watch List box, type the stock symbol for the stock you want to add to the watch list. Valid values include STOCK0 through STOCK9 as the stock symbol.
2. Press ENTER.

To remove a stock from the watch list

1. Click the Watch List button.
2. In the watch list, click the X symbol next to the stock that you want to remove.

To buy or sell shares from a stock

1. In the Position area, click the + or – symbol next to the stock that you want to buy or sell.
2. In the Buy & Sell area, enter the following data:
   1. In the Shares box, type the number of shares you want to buy or sell.
   2. In the Price Limit box, type the appropriate price.
   3. In the Order Type drop-down box, click Limit, Market, or Stop.
   4. In the Term box, click End of day or Thirty days. Term is the length of time an order will be active before it is carried out or it expires.
3. To submit the order, click the Submit button. To cancel the order, click the Cancel button.

To submit or cancel all your buy and sell orders

• If you have multiple orders that are ready to be bought or sold, the Submit All and Cancel All buttons are enabled on the Buy & Sell area and on the main task bar. The Submit All button will be enabled only if all individual orders are able to be submitted.

The following illustration shows the Stock Trader RI Buy & Sell tab.

Buy & Sell area in the Stock Trader RI

Acceptance Tests

The Stock Trader RI includes a separate solution that includes acceptance tests. The acceptance tests describe how the reference implementation should perform when you follow a series of steps. You can use the acceptance tests to explore the functional behavior of the application in a variety of scenarios.

Outcome

You should see the Stock Trader RI shell window and the tests automatically interact with the application. At the end of the test pass, you should see that all tests have passed.

The Scenario

The Stock Trader RI illustrates a fictitious, but realistic financial investments scenario. Contoso Financial Investments (CFI) is a fictional financial organization that is modeled after real financial organizations. CFI is building a new composite application to be used by their stock traders. This topic contains a summary of the scenario and demonstrates the business drivers that led to a series of technical decisions that ultimately result in the use of Prism.

Contoso Financial Investments Scenario

Contoso Financial Investments (CFI) is a global investment firm with one hundred traders. Core to doing business in CFI, there is a 15-year-old legacy trader application developed in Visual C++ with the Microsoft Foundational Class Library that, over time, has become increasingly difficult to maintain.

Operating Environment

For the last several years, CFI's lack of maintainability has brought new development on the application to a standstill—this has left the application in maintenance mode. To meet new customer requirements, CFI adopted the Microsoft .NET Framework development platform and branched out, creating additional applications that were each maintained by separate teams in a silo. The idea was that having separately developed applications would actually result in the development effort being more efficient. Each team developing in their own silo meant that CFI could remove any contention that might arise, and it would pave the way for easily creating new teams. This would allow CFI to scale out their development teams into several locations, including setting up several offshore teams.

The harsh reality is that the approach proved to be extremely inefficient on several levels. Because each application was developed in a silo, the trader is now required to maintain multiple copies of the same data throughout a growing suite of applications, including StockPortfolio, MarketView, and StockHist. The data is not identical, but there are elements of the data that are duplicated. To do their jobs, traders constantly jump back and forth between these various applications. To assist with this, CFI employed a "launcher" that quickly launched all the applications from a central place. The launcher also passed the user's logon credentials to the application to skip the logon screen for each application. The launcher is more of a bandage than anything else. It did not greatly improve the overall workflow of the traders in that the applications cannot integrate with one another, nor do they support a consistent UI.

Operational Challenges

Because of the lack of integration, getting a consolidated view of all the related data is not an easy task. There is a customer-facing reporting site that can pull from each of the back-end systems to create this "one" view, but it is littered with problems, the least of which is that if the data has not been properly duplicated, the reports do not work. In addition, entering the duplicate data is extremely time consuming and significantly impacts the number of orders that the trader is processing. Manually entering the data caused many errors in the system. Attempts to automatically synchronize the different systems have been too costly, because the schemas are very different and change frequently. With all these problems, CFI, like many other businesses, has managed to continue to operate as a profitable business. As customer demand has increased, CFI has invested the necessary funds to expand its services. It has also consistently grown its trading force whose jobs have become more and more difficult because of the inefficient operating conditions. Recently, however, this inefficiency has increased to the point that the business is starting to lose money:

• The interaction time per transaction has greatly increased because of the time it takes to navigate the suite of applications.
• The cost of employee training and in-house support has greatly increased because of the high complexity and lack of consistency of the applications.
• Maintenance costs of the various applications are extremely prohibitive. For example, in a recent instance, a logic bug that was detected required changes in seven different systems. This critical bug took three weeks to fix because other parts of the system heavily depended on the code where the bug resided. This greatly increased the cost of fixing it, testing it, and deploying it—it brought the total price to $150,000. This included the effort to fix three additional bugs that were created as part of the original fix.
• CFI has been unable to keep up with emerging technologies that can offer it a competitive edge and reduced development costs.

Emerging Requirements

Currently, CFI is faced with a new challenge around Service-Oriented Architecture (SOA). Fabrikam Web Traders, one of CFI's chief competitors, has offered its customers a rich client desktop experience for managing their portfolios remotely and on-site. The client is able to access Fabrikam's back-end systems through web services. Several large CFI customers are now requesting the same capabilities.

Although there is no immediate threat, in the long term, the business impact can be crippling. If CFI continues with the current strategy and does not both improve its efficiency and adapt to changing market conditions, it will lose business to its competition.

Meeting the Business and IT Objectives

The Chief Executive Officer (CEO) is an opportunist who sees this challenge as an opportunity for CFI to rise to the occasion. Working with the Chief Information Officer (CIO) and Chief Technology Officer (CTO), they devise a three-point strategy for moving CFI forward. The strategy is as follows:

• Reduce the cost of development. To do this, the new system should do the following:
  • It should provide structure for teams to collaborate through a well-defined architecture.
  • It should support distributed teams, including using some offshore developers.
  • It should provide a shorter development life cycle—this improves the time to market.
  • It should present data in ways that were previously prohibitive and time consuming to implement.
  • It should support Test-Driven Development (TDD).
  • It should support automated acceptance tests.
  • It should support integration with third-party systems.
• Improve trader efficiency. To accomplish this, the system should do the following:
  • It should support better multitasking.
  • It should provide a UI that is better adapted to the trader workflow.
  • It should consolidate existing applications.
  • It should provide shorter interaction time per transaction (data visualizations).
  • It should provide better information flow (contextual UI queues).
  • It should provide better use of screen area (also known as screen real estate).
  • It should provide integration among the different components of the system and with external components (services).
  • It should present reduced training time.
  • It should support users whether they are located remotely or are on-site.
  • It should support corporate branding and UI styling.
  • It should minimize the cost of adding new functionality to the system.
  • It should support adding custom extensions provided by either the customer or third-party companies.
• Create a new customer-facing product offering. This offering should do the following:
  • It should include a rich client desktop experience for portfolio management.
  • It should provide UI customization and corporate branding to beat out the competition.
  • It should provide extensibility for third-party vendors.

The CTO has delivered these requirements to the senior architect, who is investigating various options for delivering them.

Development Challenges

For the architect, this project represents one of the most significant changes in the technology environment of CFI. Work will be spread across several software development teams, with additional development being outsourced. In the past, cooperation between the development teams has been limited, and development tended to occur on an ad-hoc basis. This was because he identified the following problems that are a result of current development methodology:

• Inconsistency. Similar applications are developed in different ways. This results in higher maintenance and training costs.
• Varying quality. Developers with varying levels of experience lack guidance on implementing proven practices. This situation results in inconsistent quality among the applications they produce.
• Poor productivity. In many cases, developers across the company repeatedly solve the same problems in different applications, with little or no reuse of code. Because there was no central design, it was very difficult to get the applications to communicate with one another.

The Solution: Prism

The senior architect needs a strategy to realize the architectural vision set forth and to resolve the development challenges identified in the previous section. After significant research, he decides that the best solution can be found in Prism offered by the Microsoft patterns & practices group.

Prism is a set of assets for building complex WPF applications. Prism enables designing a composite application in the following ways:

• It provides infrastructure and support for developing and maintaining WPF composite applications through non-invasive and lightweight APIs.
• It dynamically composes UI components.
• It supports application modules that are developed, tested, and deployed by separate teams.
• It allows incremental adoption.
• It provides an integrated and consistent user experience.
• It can be integrated with existing WPF applications.
• It supports a multi-targeted scenario.

Prism from Microsoft patterns & practices meets the requirements of CFI and should allow them to achieve their goals by making development significantly more efficient and predictable. Support for integrating with existing WPF applications is of particular interest to the architect because CFI recently developed several WPF applications to address recent customer needs. He is confident that the guidance will assist him in delivering an effective solution that is robust, reliable, based on proven practices, and that can best use WPF . After presenting his findings to the CTO, the CTO agrees that Prism will help to deliver an effective solution efficiently and cost-effectively. He gives approval for the project to proceed.

Stock Trader RI Features

The CFI stock trader application is used for managing a trader's portfolio of investments. Using the stock trader application, traders can see their portfolios, view trend data, buy and sell shares, manage items in their watch lists, and view related news.

The Stock Trader RI supports the following actions:

• See the pie chart and line chart for each stock.
• See a news item that corresponds to a stock.
• Add a stock to the watch list.
• View the watch list.
• Remove a stock from the watch list.
• Buy or sell shares from a stock.
• Submit or cancel your entire buy and sell orders.

Logical Architecture

The following illustration shows a high-level logical architecture view of the Stock Trader RI.

Architectural view of the Stock Trader RI

The Stock Trader RIuses Prism Library for WPF.

The following describes the main elements of the Stock Trader RI architecture:

• Application. The application is lightweight and contains the shell that hosts each of the different UI components within the reference implementation. It also contains the StockTraderRIBootstrapper, which sets up the container and initializes module loading.
• Modules. The solution is divided into the following four modules, which are each maintained by separate teams in different locations:
  • Watch module. The Watch module contains the Watch List and Add To Watch List functionality.
  • News module. The News module contains the NewsFeedService, which handles retrieving stock news items.
  • Market module. The Market module handles retrieval of market trend data for the trader's positions and notifies the UI when those positions change. It also handles populating the Trend line for the selected position.
  • Position module. The Position module handles populating the list of positions in the trader's portfolio. It also contains the Buy/Sell order functionality.
• Infrastructure. The infrastructure contains functionality for both the Stock Trader RI and the Prism core:
  • Prism Library. This contains the core composition services and service interfaces for handling regions, commanding, and module loading. It also contains the container façade for the Unity Application Block (Unity) and MEF. The StockTraderRIBootstrapper inherits from the MefBoostrapper.
  • Stock Trader RI Infrastructure Library. This contains service interfaces specific to the Stock Trader RI, shared models, and shared commands.

Implementation View

The Stock Trader RI is based on the Prism Library. The following illustration shows the Stock Trader RI (Desktop version) Solution Explorer.

Stock Trader RI solution view

How the Stock Trader RI Works

The Stock Trader RI is a composite application, which is composed of a set of modules that are initialized at run time. The following illustration shows the application's startup process, which includes the initialization of modules. The next sections provide details about each of these steps.

Stock Trader RI startup process

The Stock Trader RI startup process is the following:

1. The application uses the StockTraderRIBootstrapper, which inherits from the Prism Library's MefBootstrapper for its initialization.
2. The application initializes the Prism Library's MefServiceLocatorAdapter for use in the modules.
3. The StockTraderRIBootstrapper creates and shows the shell view.
4. The Prism Library's ModuleCatalog finds all the modules the application needs to load.
5. The Prism Library's ModuleManager loads and initializes each module.
6. Modules use the Prism Library's RegionManager service to add a view to a region.
7. The Prism Library's Region displays the view.

Modules

A module is a logical unit of separation in the application. In the Stock Trader RI, each module exists in a separate assembly, but this is not an absolute requirement. The advantage of having this separation is that it makes the application more maintainable and enables distributed teams to work on different modules with minimal overlap on the files being updated in the source control system.

The application does not directly insert views from each module into the shell; instead, each module contributes content to the shell view and interacts with other modules. The final system is composed of the aggregation of the modules' contributions. By using composition, you can create applications with emergent behaviors—this refers to the application being able to scale up in complexity and requirements as it grows.

The modules are loosely coupled. This means they do not directly reference each other, which promotes separation of concerns and allows modules to be individually developed, tested, and deployed by different teams.

Services and Containers

This is possible through a set of application services that the modules have access to. Modules do not directly reference one another to access these services. In the Stock Trader RI, a dependency injection container (referred to as the container) injects these services into modules during their initialization (the Stock Trader RI uses the MEF container).

Bootstrapping the Application

Modules get initialized during a bootstrapping process by a class named MefBootstrapper. The MefBootstrapper is responsible for starting the core composition services used in an application created with the Prism Library. The following code from the MefBootstrapper class shows how the Module Manager is located from the container.

// MefBootstrapper.cs
protected override void InitializeModules()
{
    IModuleManager manager = this.Container.GetExportedValue<IModuleManager>();
 
    manager.Run();
}

The Module Manager manages the process of validating the module catalog, retrieving modules if they are remote, loading the modules into the application domain, and calling the IModule.Initialize method.

Configuring the Aggregate Catalog

The StockTraderRIBootstrapper class configures the AggregateCatalog in code. In this case, the shell has direct references to all the modules, so the StockTraderRIBootstrapper can directly add them to the AggregateCatalog. The StockTraderRIBootstrapper also adds its own assembly to the catalog so that types exported within the application are available in the container.

// StockTraderRIBootstrapper.cs
protected override void ConfigureAggregateCatalog()
{
    this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(StockTraderRIBootstrapper).Assembly));
    this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(StockTraderRICommands).Assembly));
    this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(MarketModule).Assembly));
    this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(PositionModule).Assembly));
    this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(WatchModule).Assembly));
    this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(NewsModule).Assembly));
}

Module Loading

After the container is populated, the types contained in each module assembly are available.

During this initialization process, the container will inject instances into types to resolve their dependencies. The following code shows how the news feed service, region manager, and event aggregator services are injected into the ArticleViewModel constructor.

// ArticleViewModel.cs
[Export(typeof(ArticleViewModel))]
[PartCreationPolicy(CreationPolicy.Shared)]
public class ArticleViewModel : BindableBase
{
    [ImportingConstructor]
    public ArticleViewModel(INewsFeedService newsFeedService, IRegionManager regionManager, IEventAggregator eventAggregator)
    {
        ...
    }
}

In addition, other types, such as services, are available so they can be accessed either by the same module or other modules in a loosely coupled fashion.

Views

A view is any content that a module contributes to the UI. In the Stock Trader RI, views are discovered at run time and added to regions. Regions are classes associated with a control container, such as ContentControl or TabControl.

View Registration in the Container

Views can be registered through declarative attributes, directly in code, or through configuration. The Stock Trader RI uses MEF and the MVVM pattern to demonstrate the use of declarative attributes. Views associate themselves with a region through a custom export attribute, as shown in the following code example.

// ArticleViewModel.cs
[ViewExport(RegionName = RegionNames.ResearchRegion)]
[PartCreationPolicy(CreationPolicy.Shared)]
public partial class ArticleView : UserControl

The AutoPopulateExportedViewsBehavior in the Stock Trader RI infrastructure discovers the views in the container and automatically populates them into the associated region, as shown in the following code example.

// AutoPopulateExportedViewsBehavior.cs
[ImportMany(AllowRecomposition = true)]
public Lazy<object, IViewRegionRegistration>[] RegisteredViews { get; set; }

public void OnImportsSatisfied()
{
    AddRegisteredViews();
}
 
private void AddRegisteredViews()
{
    if (this.Region != null)
    {
        foreach (var viewEntry in this.RegisteredViews)
        {
            if (viewEntry.Metadata.RegionName == this.Region.Name)
            {
                var view = viewEntry.Value;
 
                if (!this.Region.Views.Contains(view))
                {
                    this.Region.Add(view);
                }
            }
        }
    }
}

Model-View-ViewModel

The Stock Trader RI uses the MVVM pattern to separate UI, presentation logic, and the data model. Using MVVM allows the view model to be unit tested because it has no direct knowledge of the view.

The Prism Library provides the BindableBase class that the view models in the Stock Trader RI use to notify the user interface of property changes. BindableBase makes implementing INotifyPropertyChanged much easier.

In the Stock Trader RI, the view and view model are connected through view discovery. The view is discovered by the AutoPopulateExportedViewsBehavior and instantiated through the container. Because the view declares an import of the view model, the container then instantiates the view model and injects it into the view, as shown in the following code example.

// ArticleView.xaml.cs
[Import]
ArticleViewModel ViewModel
{          
    set
    {
        this.DataContext = value;
    }
}

For more information about view discovery, see Composing the User Interface.

Commands

Views can communicate with presenters and services in a loosely coupled fashion by using commands. The Add To Watch List control, as shown in the following illustration, uses the AddWatchCommand, which is a DelegateCommand, to notify the WatchListService whenever a new watch item is added.

Add To Watch List control

Using a DelegateCommand allows the service to delegate the command's Execute method to the service's AddWatch method, as shown in the following code example.

// WatchListService.cs
public WatchListService(IMarketFeedService marketFeedService)
{
    ...
    AddWatchCommand = new DelegateCommand<string>(AddWatch);
    ...
}

private void AddWatch(string tickerSymbol)
{
    ...
}

The WatchListService is also injected into the AddWatchViewModel, which exposes the command to the view.

// AddWatchViewModel.cs
public class AddWatchViewModel : BindableBase
 {
     private string stockSymbol;
     private IWatchListService watchListService;
 
     [ImportingConstructor]
     public AddWatchViewModel(IWatchListService watchListService)
     {
         if (watchListService == null)
         {
             throw new ArgumentNullException("service");
         }
         this.watchListService = watchListService;
     }
 
     public string StockSymbol
     {
         get { return stockSymbol; }
         set
         {
             SetProperty(ref stockSymbol, value);         
         }
     }
 
    public ICommand AddWatchCommand { get { return this.watchListService.AddWatchCommand; } }
}

The AddWatchButton in the view then binds to the AddWatchViewModel command through the DataContext.

<!--AddWatchView.xaml -->
<StackPanel Orientation="Horizontal">
    <TextBox Name="AddWatchTextBox" MinWidth="100" Style="{StaticResource CustomTextBoxStyle}" 
        Infrastructure:ReturnKey.Command="{Binding Path=AddWatchCommand}" 
        Infrastructure:ReturnKey.DefaultTextAfterCommandExecution="Add to Watch List" 
        Text="Add to Watch List" 
        AutomationProperties.AutomationId="TextBoxBlock" Margin="5,0,0,0"/>
</StackPanel>

This is using an attached behavior on the Add To Watch List text box, so when the user enters a stock symbol and then presses ENTER**,** the AddWatchCommand will be invoked, thereby passing the stock symbol to the WatchListService. For more information about attached behaviors, see Command Behaviors in Advanced MVVM Scenarios.

Event Aggregator

The Event Aggregator pattern channels events from multiple objects through a single object to simplify registration for clients. In the Prism Library, a variation of the Event Aggregator pattern allows multiple objects to locate and publish or subscribe to events.

In the Stock Trader RI, the event aggregator is used to communicate between modules. The subscriber tells the event aggregator to receive notifications on the UI thread. For example, when the user selects a symbol on the Position tab, the PositionSummaryViewModel in the Position module raises an event that specifies the symbol that was selected, as shown in the following code example.

// PositionSummaryViewModel.cs
eventAggregator.GetEvent<TickerSymbolSelectedEvent>().Publish(CurrentPositionSummaryItem.TickerSymbol);

The ArticleViewModel in the News module listens to the event to display the news related to the selected symbol, as shown in the following code example.

// ArticleViewModel.cs
eventAggregator.GetEvent<TickerSymbolSelectedEvent>().Subscribe(OnTickerSymbolSelected, ThreadOption.UIThread);

Technical Challenges

The Stock Trader Reference Implementation (Stock Trader RI) demonstrates how you can address common technical challenges that you face when you build composite applications in WPF. The following table describes the technical challenges that the Stock Trader RI addresses.

Technical challenge	Feature in the Stock Trader RI	Example of where feature is demonstrated
Views and composite UI
Regions: The use of regions for placing the views without having to know how the layout is implemented.	Regions defined in the shell and position module's orders view.	StockTraderRI\Shell.xaml StockTraderRI.Modules.Position\Orders\OrdersView.xaml
Composite view: Shows how a composite view communicates with its child view.	Order screen	StockTraderRI.Modules.Position\Orders\OrderCompositeViewModel.cs StockTraderRI.Modules.Position\Orders\OrderDetailsViewModel.cs StockTraderRI.Modules.Position\Orders\OrderCommandsView.xaml.cs
Compose UI across modules: Shows how a module can have views in different parts of the shell that interact with each other.	The Watch module has a view and also is a part of the toolbar.	StockTraderRI.Modules.Watch\AddWatch\AddWatchView.xaml StockTraderRI.Modules.Watch\WatchList\WatchListView.xaml
	The News module has an article list view and a popup article reader view that shows the same articles.	StockTraderRI.Modules.News\Article\ArticleView.xaml StockTraderRI.Modules.News\Article\NewsReader.xaml
Decoupled communication
Commands: Shows the Command pattern. The command to buy or sell a stock is a delegate command. Each row in the list uses the same command instance but with a different parameter corresponding to the stock. This decouples the invoker from the receiver and shows passing additional data with the command.	Buy and Sell command invokers in PositionSummaryView and handlers in OrdersController	StockTraderRI.Modules.Position\Controllers\OrdersController.cs StockTraderRI.Modules.Position\PositionSummary\PositionSummaryView.xaml
Composite commands: Use composite commands to broadcast all of the commands. The Submit All or Cancel All commands execute all the individual instances of the Submit or Cancel commands.	Submit All and Cancel All buttons	StockTraderRI.Infrastructure\StockTraderRICommands.cs StockTraderRI.Modules.Position\Orders\OrderDetailsViewModel.cs StockTraderRI.Modules.Position\Controllers\OrdersController.cs
Event Aggregator pattern: Publish and Subscribe to events across decoupled modules. Publisher and Subscriber have no contract other than the event type.	Show relevant news content: When the user selects a position in the position list, the communication to the news module uses the EventAggregator service.	StockTraderRI.Modules.Position\PositionSummary\PositionSummaryPresentationModel.cs StockTraderRI.Modules.News\Controllers\NewsController.cs
	Market feed updates: The consumers of the market feed service subscribe to an event to be notified when new feeds are available; the consumers then update the model behind the UI.	StockTraderRI.Modules.Market\Services\MarketFeedService.cs StockTraderRI.Modules.Position\PositionSummary\ObservablePosition.cs StockTraderRI.Modules.Watch\WatchList\WatchListViewModel.cs
Services: Services are also used to communicate between modules. Services are more contractual and flexible than commands.	Several service implementations in module assemblies	Services: StockTraderRI.Modules.Market\Services\MarketFeedService.cs StockTraderRI.Modules.Market\Services\MarketHistoryService.cs StockTraderRI.Modules.News\Services\NewsFeedService.cs StockTraderRI.Modules.Watch\Services\WatchListService.cs StockTraderRI.Modules.Position\Services\AccountPositionService.cs StockTraderRI.Modules.Position\Services\XmlOrdersService.cs
Other technical challenges
WPF: Use WPF for the user interface	Shell and module views	The starting point for Stock Trader RI - Desktop version is in the StockTraderRI\App.xaml.cs
Bootstrapper: The use of a bootstrapper to initialize the application with global services.	Created bootstrapper with MEF and configuring global services, such as logging and defining the module catalog.	Bootstrapper: StockTraderRI\StockTraderRIBootstrapper.cs

Unit and Acceptance Tests

The Stock Trader RI includes unit tests within the solution. Unit tests verify whether individual units of source code work as expected.

To run the Stock Trader RI unit tests

• On the Test menu, point to Run, and then click All Tests in Solution.

The Stock Trader RI includes a separate solution that includes acceptance tests. The acceptance tests describe how the application should perform when you follow a series of steps; you can use the acceptance tests to explore the functional behavior of the application in a variety of scenarios.

To run the Stock Trader RI acceptance tests

1. In Visual Studio, open the solution file StockTrader RI\StockTraderRI.Tests.AcceptanceTest\StockTraderRI.Tests.AcceptanceTest.sln.
2. Build the solution.
3. Open Test Explorer.
4. After building the solution, the test will be found. Click the Run All button to run the acceptance tests.

Outcome

You should see the reference implementation window and the tests automatically interact with the application. At the end of the test run, you should see that all tests have passed.

More Information

To learn about other code samples included with Prism, see the following topics:

• Modularity QuickStarts
• Interactivity QuickStart
• MVVM QuickStart
• Commanding QuickStart
• UI Composition QuickStart
• State-Based Navigation QuickStart
• View-Switching Navigation QuickStart
• Event Aggregation QuickStart

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