Csharp 嵌套 CollectionView 或在集合视图内显示嵌套数据

您可以重新判断是否可以正确获取内部列表数据(Child).

根据您的代码，我制作了一个实现此功能的演示，它可以正常工作.

您可以参考以下代码:

public partial class MyViewModel:ObservableObject 
{
    [ObservableProperty]
    public List<Items> data;

    public MyViewModel()
    {
        List<Items> Childs = new List<Items>();

        Childs.Add(new Items { itemNumber = 01 - 1, itemdescr = "desc-01-1" });
        Childs.Add(new Items { itemNumber = 02 - 1, itemdescr = "desc-02-1" });
        Childs.Add(new Items { itemNumber = 03 - 1, itemdescr = "desc-03-1" });

        Data = new List<Items>();
        Data.Add(new Items { itemNumber= 01, itemdescr ="desc-01",Child= Childs });
        Data.Add(new Items { itemNumber= 02, itemdescr ="desc-02", Child = Childs });
        Data.Add(new Items { itemNumber= 03, itemdescr ="desc-03", Child = Childs });
        Data.Add(new Items { itemNumber= 04, itemdescr ="desc-04" , Child = Childs });
        Data.Add(new Items { itemNumber= 05, itemdescr ="desc-05" , Child = Childs });
        Data.Add(new Items { itemNumber= 06, itemdescr ="desc-06" , Child = Childs });
        
    }
}

用途:

<?xml version="1.0" encoding="utf-8" ?> 
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="MauiMVVMToolkitApp.MyPage"
             xmlns:viewmodel="clr-namespace:MauiMVVMToolkitApp.ViewModels"
             xmlns:mct="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
             Title="MyPage">

    <ContentPage.BindingContext>
        <viewmodel:MyViewModel></viewmodel:MyViewModel>
    </ContentPage.BindingContext>
    <VerticalStackLayout>
        <CollectionView x:Name="CollectionViewBoM" Grid.Row="1" Grid.Column="0" Grid.ColumnSpan="9" ItemsSource="{Binding Data}">
            <CollectionView.ItemTemplate>
                <DataTemplate >
                    <mct:Expander >
                        <mct:Expander.Header>
                            <Grid HeightRequest="45" MaximumHeightRequest="90" ColumnSpacing="1" RowSpacing="2">
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width="240"/>
                                    <ColumnDefinition Width="*"/>
                                </Grid.ColumnDefinitions>
                                <!--<BoxView Grid.Column="0" />
                                <BoxView Grid.Column="1" />-->
                                <Label  Grid.Column="0" Text="{Binding itemNumber}" />
                                <Label  Grid.Column="1" Text="{Binding Description}" />
                            </Grid>
                        </mct:Expander.Header>
                        <mct:Expander.Content x:Name="CollectionViewChild">
                            <StackLayout BindableLayout.ItemsSource="{Binding Child}">
                                <BindableLayout.ItemTemplate>
                                    <DataTemplate>
                                        <HorizontalStackLayout>
                                            <Label Text="{Binding itemNumber}" />
                                            <Label Text="{Binding itemdescr}"  Margin="10,0,0,0"/>
                                        </HorizontalStackLayout>
                                    </DataTemplate>
                                </BindableLayout.ItemTemplate>
                            </StackLayout>
                        </mct:Expander.Content>
                    </mct:Expander>
                </DataTemplate>
            </CollectionView.ItemTemplate>
        </CollectionView>
    </VerticalStackLayout>
</ContentPage>

注:

为了代码简洁，我注释掉了两个BoxView的布局.

此外，我注意到类Items还应该包含另一个属性 Description，并且类Items(Child)的属性，其内部的子元素也是类型Items.初始化数据时请注意这一点.