好吧，我不确定这是否是您想要实现的目标，但您可以尝试以下方法:

Well, I am not sure if this is what you want achieve but here is a way that you can try:

假设你的课程是这样的:

Assuming your classes are like these:

public class Group
{
    public string Name { get; set; }
    public List<Contact> Contacts { get; set; }
}

public class Contact
{
    public string Name { get; set; }
    public bool IsOnline { get; set; }
}

您可以将 ListBox.ItemTemplate 设置为另一个 ListBox 绑定到 Contacts 属性，例如:

You can set ListBox.ItemTemplate as another ListBox bind to Contacts property, like:

<CollectionViewSource x:Key="groups" Source="{Binding}" >
    <CollectionViewSource.GroupDescriptions>
        <PropertyGroupDescription PropertyName="Name" />
    </CollectionViewSource.GroupDescriptions>
</CollectionViewSource>

<DataTemplate x:Key="groupTemplate" DataType="Group">
    <StackPanel Orientation="Horizontal">
        <TextBlock Text="{Binding Name}" />
    </StackPanel>
</DataTemplate>

<ListBox ItemsSource="{Binding Source={StaticResource groups}}">
    <ListBox.GroupStyle>
        <GroupStyle HeaderTemplate="{StaticResource groupTemplate}" />
    </ListBox.GroupStyle>
    <ListBox.ItemTemplate>
        <DataTemplate DataType="Contact">
            <ListBox ItemsSource="{Binding Contacts}">
                <ListBox.ItemTemplate>
                    <DataTemplate DataType="Contact">
                        <TextBlock Text="{Binding Name}" />
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

您必须稍微设置内部列表框的样式.

You have to style the inner listbox a little bit.

Edit:使用TreeView

<DataTemplate DataType="Contact">
   <TextBlock Text="{Binding Name}" />
</DataTemplate>

<TreeView ItemsSource="{Binding Source={StaticResource groups}}">
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate DataType="Group" ItemsSource="{Binding Contacts}">
            <TextBlock Text="{Binding Name}" />
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>