Avalonia 模板里面绑定ViewModel跟WPF写法有些不同。需要单独绑定Command.

WPF里面可以直接按照下面的方法绑定DataContext.

 <Button Content="Button" Command="{Binding DataContext.ClickCommand, RelativeSource={RelativeSource AncestorType={x:Type UserControl}}}" CommandParameter="{Binding ID}" />

Avalonia得改成下面这样，单独写Command，在DataContexe前面要加上对应VIewMode强制转换。

					<DataTemplate ><Button CommandParameter="{Binding Value}"Content="{Binding Label}"><Button.Command><Binding  Path="((vm:MessagViewModel)DataContext).ButtonClicked" RelativeSource="{RelativeSource AncestorType=Window}" /></Button.Command></Button></DataTemplate>