Avalonia/samples/IntegrationTestApp/App.axaml

<Application xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:self="using:IntegrationTestApp"
             x:Class="IntegrationTestApp.App"
             x:DataType="self:App"
             RequestedThemeVariant="Default">
    <Application.Styles>
        <FluentTheme />
    </Application.Styles>
    <TrayIcon.Icons>
        <TrayIcons>
            <TrayIcon Icon="/Assets/icon.ico"
                      ToolTipText="IntegrationTestApp TrayIcon"
                      Command="{Binding TrayIconCommand}"
                      CommandParameter="TrayIconClicked">
                <TrayIcon.Menu>
                    <NativeMenu>
                        <NativeMenuItem Header="Raise Menu Clicked"
                                        Command="{Binding TrayIconCommand}"
                                        CommandParameter="TrayIconMenuClicked" />
                    </NativeMenu>
                </TrayIcon.Menu>
            </TrayIcon>
        </TrayIcons>
    </TrayIcon.Icons>
</Application>