Avalonia/samples/ControlCatalog/Pages/DragAndDropPage.xaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="ControlCatalog.Pages.DragAndDropPage">
    <StackPanel Orientation="Vertical" Spacing="4">
        <TextBlock Classes="h1">Drag+Drop</TextBlock>
        <TextBlock Classes="h2">Example of Drag+Drop capabilities</TextBlock>

        <StackPanel Orientation="Horizontal"
                Margin="0,16,0,0"
                HorizontalAlignment="Center"
                Spacing="16">
            <Border BorderBrush="{DynamicResource ThemeAccentBrush}" BorderThickness="2" Padding="16" Name="DragMe">
                <TextBlock Name="DragState">Drag Me</TextBlock>
            </Border>
            <Border Background="{DynamicResource ThemeAccentBrush2}" Padding="16" 
                    DragDrop.AllowDrop="True">
                <TextBlock Name="DropState">Drop some text or files here</TextBlock>
            </Border>
        </StackPanel>
    </StackPanel>
</UserControl>