C# WPF组合框Mvvm绑定

我正在尝试将列表中的选定值输入到命令中。是否有简单的方法将commandparameter绑定到所选项

<ComboBox HorizontalAlignment="Left" Margin="-56,10,0,0" VerticalAlignment="Top" Width="120" SelectedIndex="0" ItemsSource="{Binding Time}">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="Loaded">
                <i:InvokeCommandAction Command="{Binding TestCommand}" CommandParameter="{Binding }"></i:InvokeCommandAction>
            </i:EventTrigger>
            <i:EventTrigger EventName="SelectionChanged">
                <i:InvokeCommandAction Command="{Binding TestCommand}" CommandParameter="{Binding }"></i:InvokeCommandAction>
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </ComboBox>

当我尝试类似的东西时

                <i:EventTrigger EventName="SelectionChanged">
                <i:InvokeCommandAction Command="{Binding TestCommand}" CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ComboBox}},Path=SelectionBoxItem}"></i:InvokeCommandAction>
            </i:EventTrigger>

奇怪，为什么会卡住？

<ComboBox x:Name="Combo" HorizontalAlignment="Left" Margin="-56,10,0,0" VerticalAlignment="Top" Width="120" SelectedIndex="0" ItemsSource="{Binding Time}">
        <i:Interaction.Triggers>
            <i:EventTrigger EventName="Loaded">
                <i:InvokeCommandAction Command="{Binding TestCommand}" CommandParameter="{Binding ElementName=Combo, Path=SelectedItem}"></i:InvokeCommandAction>
            </i:EventTrigger>
            <i:EventTrigger EventName="SelectionChanged">
                <i:InvokeCommandAction Command="{Binding TestCommand}" CommandParameter="{Binding }"></i:InvokeCommandAction>
            </i:EventTrigger>
        </i:Interaction.Triggers>
    </ComboBox>

如果为组合框指定名称，则可以使用

ElementName

绑定并绑定到路径

SelectedItem