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Version: 11.0.0

The Main Window

You can now start your tour of an Avalonia project. We'll start with the main application window. Open the MainWindow.axaml file.

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Notice that in Avalonia, XAML files have the extension .axaml (and not .xaml). This represents 'Avalonia XAML' and the file extension was introduced for technical reasons.

What is Happening?​

In the MainWindow.axaml XAML file, the <Window>...</Window> XAML tag represents an Avalonia window. Like other Avalonia controls; the window will be drawn on the target platform with 4 layout zones: margin, border, padding and content.

In the current application, the content zone of the window references another view: . This is a reference to the MainView.axaml file, which is a user control that will be displayed in the content zone of the window.

The MainView User Control​

Inside this user control, you will see a <TextBlock>...</TextBlock> XAML tag. This represents a text block control. The Text property of the text block is bound to the Greeting property of the MainViewModel class. This is a property that will be set in the constructor of the view model class.

<TextBlock Text="{Binding Greeting}" HorizontalAlignment="Center" VerticalAlignment="Center"/>

You can change the text in the file MainViewModel.cs to see the change reflected in the user interface.

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For more information about the concept of control layout zones, see here.

The Visual Studio Designer​

If you're using Visual Studio you should see the XAML code and preview pane. Navigate to the MainView.axaml file and click the Split View button at the top of the editor window.

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There may be a red exclamation icon (top left) and the message The designer is loading.... This indicates that the project must be built before the preview pane will respond.

  • Build the project.
  • Scroll the preview pane to the left to view the preview outline and the text displayed in the top left corner.
  • Remove the binding {Binding Greeting} and change the text <TextBlock Text="my text" ...

You will see the new text in the preview pane change as you type. This is an example of the Avalonia design-time preview behaviour that will help you develop user interface presentation accurately and quickly.

  • Run the project to see your new text also appear at runtime.

On the next page you will see how to add a simple button to the window.