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Longhorn Developer Details Released

Microsoft is now releasing more details on how to build Longhorn desktop applications—and pushing developers to crack open the early SDK.

Longhorn details are no longer quite so close to the vest as Microsoft is now releasing more details on how to build Longhorn desktop applications—and pushing developers to crack open the early SDK, and start writing code with some of the pre-release tools.

The latest Microsoft revelations, posted through MSDN, position Longhorn development as an evolution of today's .NET managed code and the Service-Oriented Architecture (SOA) approach to development, rather than a revolutionary break with the past.

If .NET wasn't enough to get Windows programmers into full object-oriented mode, Longhorn, which is entirely based on the .NET framework, may be the push they need.

The new Longhorn object-oriented application model is anchored by the Application object which offers all the services that simple applications require. And if the application is rudimentary, it can be built as a series of markup pages written in Extensible Application Markup Language (XAML), an extension of XML. Fancier programs can combine XAML pages with managed procedural code, or be written entirely in procedural code. Either way, they will rely upon the NavigationApplication object, which supports navigation and state management, and inherits all the attributes of the simpler Application object.

.NET promised a day when one application could run in several environments, whether Windows desktops, mobile devices, or as a Web service. Longhorn continues that track; its tools can produce several styles of output files, including freestanding browser apps, DLLs, console apps, and desktop EXE files.

Those wanting to code XAML-compatible apps today have three main choices; C#, Jscript .NET, and Visual Basic. But if the app is 100 percent procedural, any .NET-compatible compiler will do.

Longhorn XAML
Text navigation is helped by the PageViewer XAML control.

XAML promises easier design of screens and user interfaces. Developers can quickly choose colors, fonts, borders and menu designs, making prototyping a snap.

One of the neatest aspects of Longhorn apps is the ability to easily render and navigate documents through the PageViewer. Unfortunately, files must be ASCII text in an XAML file that is wrapped in a presentation subsystem control (Avalon). Forget about simply importing a raw HTML file-at least for now.

About the Author

Doug Barney is editor in chief of Redmond magazine and the VP, editorial director of Redmond Media Group.

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