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Version: 11.0.0

Respond to an Event

There are a number of ways you can implement actions in an Avalonia application. On this page, you will see how to use one of the simplest: how to write event handling code for a button click.

To start, you will write a button click event handler that does not interact with any of the other controls.


The XAML file for the main window has a C# code-behind file associated with it. If you're using an IDE, you can find this file in the Solution Explorer - it is a sub-item of the .axaml file.

To change the code-behind for the main window:

  • Open the MainWindow.axaml.cs file

You will see some C# code like this:

using Avalonia.Controls;

namespace GetStartedApp
public partial class MainWindow : Window
public MainWindow()

The partial class MainWindow corresponds to the window object that is created by Avalonia UI as a result of the XAML you already have. You can find this class name in the XAML window tag:

x:Class="GetStartedApp.MainWindow" >

To add an event handler for the button, follow this procedure:

  • Locate the MainWindow constructor in the code-behind file for the main window (see above instructions).
  • After the constructor add the following code:
public void ButtonClicked(object source, RoutedEventArgs args)

This will require some additional using statements:

using Avalonia.Interactivity;
using System.Diagnostics;
  • Switch to the XAML file and locate the <Button> tag.
  • Enter the click attribute at the end of the tag, as follows:

If you're using an IDE you will see the Avalonia UI Intellisense as you type.

  • Run the app and click the button.

You should see the result on the Output window for Debug, like this:

On the next page, you will see how to use code-behind to read and change the properties of Avalonia UI controls at runtime.