Windows Store MVVM Development with the Okra App Framework v0.9.7

After a bit of hiatus, the latest version of the Okra App Framework has been released. The v0.9.7 release of the Windows Store centric MVVM framework targets Windows 8.1, and focuses on tidying up some of the API surface prior to an upcoming v1.0 release.

How to Get The Okra App Framework

You can download the latest version of the Okra App Framework,

• From NuGet: For the complete MVVM framework add the “Okra App Framework” NuGet package to your project.
• Using the Visual Studio Extension: The official Okra App Framework Visual Studio extension has been updated for the latest release with all new project and item templates targeting Windows 8.1. Look for the “Windows Store MVVM Templates for the Okra App Framework” extension in the Visual Studio gallery or directly from the Extensions and Updates manager in Visual Studio.

New Features in This Release

• The big change with this update is that the Okra App Framework is now targeting Windows 8.1 development. The framework makes the most of the recent improvements in the underlying operating system, with a number of changes reflecting the new API surface. Note however that this release no longer supports Windows 8.0 projects, which should continue to use v0.9.6.
• All new Windows 8.1 project and item templates for Visual Studio. These are based upon the Visual Studio 2013 templates, but rewritten to take advantage of the MVVM pattern.
• The Okra Data Framework is now available as a separate download (see the “Okra App Framework (Data Framework)” package in NuGet) so you can choose to use this independently of the core framework if desired.

Code Changes When Updating From v0.9.6

In readiness for a v1.0 release, a number of breaking changes have been made,

• To simplify page activation the IActivatable interface in no longer generic. Instead of directly passing the page arguments and state, a PageInfo object is used instead.

// Old code using the Okra App Framework v0.9.6

public class MyViewModel : ViewModelBase, IActivatable<string, string>

{

    ...

    public void Activate(string arguments, string state)

    {

        this.Photo = GetPhoto(arguments);

        this.State = state;

    }

    public string SaveState()

    {

        return this.State;

    }

}

// New code using the Okra App Framework v.0.9.7

public class MyViewModel : ViewModelBase, IActivatable

{

    ...

    public void Activate(PageInfo pageInfo)

    {

        string arguments = pageInfo.GetArguments<string>();

        this.Photo = GetPhoto(arguments);

        this.State = pageInfo.GetState<string>("MyState");

    }

    public void SaveState(PageInfo pageInfo)

    {

        pageInfo.SetState<string>("MyState", this.State);

    }

}

• To allow more flexible navigation patterns a number of properties and methods have been moved from INavigationBase to INavigationStack (accessible from any INavigationBase via the NavigationStack property).
• Since the Windows 8.1 update includes a system provided SettingsFlyout control, you no longer need to wrap any settings pages in a SettingsChrome control.