CLI300: Building Avalon Apps with Controls and Dialogs

  • Article

When you install the Longhorn Developer Preview SDK, it adds a number of new project
templates to the VB and C# IDE:

- application

custom control
  • document project
  • hosted application
  • navigation application
  • screen saver
  • sidebar tile.

Within a project, you can easily add different XAML files based on a series of pre-defined
templates.

Here's a very basic example of a XAML window definition:

    
   <FlowPanel xmlns="https://schemas.microsoft.com/2003/xaml">
   Here's a listbox: <ListBox ID="listBox1">
   <ListItem>Item1</ListItem>
   </ListBox>
   </FlowPanel>

You can create styles for items (to set a consistent look or feel across multiple
instances of a control). These are created within a .resources element that matches
the panel (e.g. <FlowPanel.Resources>). These are called compound property
tags.

What happens when you build a XAML-enabled application? The XAML gets turned into
two separate things: a .g.cs file (which is a partial class containing any code that
you've included in the XAML file), and a .baml file (which contains a binary pre-processed
representation of the rest of the XAML). The .g.cs file gets compiled in combination
with any code-behind class you have to produce the final .exe.

There are five element families: controls, panels, decorators, shapes and content
elements. Each of these primitives can be subclassed to modify the standard behaviour.

Panels come in a number of different styles: DockPanel, GridPanel, FlowPanel, TablePanel
and Canvas are all included with the Longhorn SDK. The DockPanel allows you to create
multiple controls that are each docked, much like the docking property of controls
in WinForms today. GridPanel provides a simple grid view that allows controls to be
aligned in multiple columns. FlowPanel simply flows controls (either horizontally
or vertically), much like IE shows HTML. Panels can be nested within other panels,
so you can mix and match different layout types within a form. Or you might have a
DockPanel within a DockPanel in order to dock items within a master panel control.

The concept of a document is far stronger in Avalon than in the traditional WinForms
environment. Like MFC, there is a view infrastructure. One clever feature is that
the SDK installs an Avalon printer driver into Longhorn that can be used to generate
these documents. So, for example, if you printed a Powerpoint slide deck with the
printer driver, it would generate a XAML document that could be rendered as part of
a form.