Avalonia/samples/IntegrationTestApp/Pages/ContextMenuPage.axaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
             x:Class="IntegrationTestApp.Pages.ContextMenuPage">
  <StackPanel>
    <Button Name="ShowContextMenu" Content="Right-click to show context menu.">
      <Button.ContextMenu>
        <ContextMenu>
          <MenuItem Name="ContextMenuItem1" Header="Item 1"/>
          <MenuItem Name="ContextMenuItem2" Header="Item 2"/>
        </ContextMenu>
      </Button.ContextMenu>
    </Button>
  </StackPanel>
</UserControl>