.NET 8 Maui CollectionView字段获取及跨页面传参咨询

我的CollectionView展示了包含CaseName、ReportName、Court和Judges的查询结果，每个单元格设有Index和Judgment两个按钮。点击任一按钮（例如第一个单元格的Index按钮）时，需要获取对应单元格的CaseName字段（如INKUMSAH V. THE REPUBLIC），并将其作为参数传递至下一页。目前用DisplayAlert验证是否成功获取CaseName，但实现存在问题，需要技术帮助。

<CollectionView x:Name="CasesCollectionView" 
                ItemsSource="{Binding ReportedCasesList}" 
                Grid.Row="2">
    <CollectionView.ItemTemplate>
        <DataTemplate>
            <Frame x:Name="frame" 
                   CornerRadius="10" 
                   Margin="10,0,10,10" 
                   HasShadow="True">
                <StackLayout>
                    <Label x:Name="Case" 
                            TextColor="Red" 
                            Text="{Binding Source={x:Reference Case}, Path=BindingContext.CaseName}"
                            FontSize="13" 
                            FontAttributes="Bold" 
                           Padding="0,0,0,10" />
                        
                    <Label x:Name="Report" 
                            TextColor="Black" 
                            FontSize="12" 
                            Text="{Binding ReportName}" />
                        
                    <Label x:Name="Court" 
                            TextColor="Black" 
                            FontSize="12" 
                            Text="{Binding CourtName}" />
                        
                    <Label x:Name="Judge" 
                            TextColor="Black" 
                            FontSize="12" 
                            Text="{Binding Judges}" 
                            HorizontalTextAlignment="End" 
                            FontAttributes="Italic" 
                            Padding="0,10,0,0" Margin="0,0,0,10" />
                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*" />
                            <ColumnDefinition Width="*" />
                        </Grid.ColumnDefinitions>
                        <Button x:Name="IndexButton" 
                                TextColor="White" 
                                BackgroundColor="Red"
                                FontSize="12" 
                                Text="Index" 
                                Grid.Column="0" Margin="5,0,5,0" 
                                Command="{Binding Source={x:Reference CasesCollectionView}, Path=BindingContext.GoToCaseIndexCommand}"/>
                        <Button x:Name="JudgmentButton" 
                                TextColor="White" 
                                BackgroundColor="Red"
                                FontSize="12" 
                                Text="Judgment" 
                                Grid.Column="1" Margin="5,0,5,0" 
                                Command="{Binding Source={x:Reference CasesCollectionView}, Path=BindingContext.GoToCaseJudgmentCommand}"/>
                    </Grid>
                </StackLayout>
            </Frame> 

        </DataTemplate>
    </CollectionView.ItemTemplate>
</CollectionView>

[ObservableProperty]
public string? caseName;


[RelayCommand]
public async Task GoToCaseIndex()
{
    if (Application.Current?.MainPage != null)
        await Application.Current.MainPage.DisplayAlert("Cases",
            CaseName, "OK");

    await Shell.Current.GoToAsync(nameof(AreasOfLawResultsPage));
}

[RelayCommand]
public async Task GoToCaseJudgment()
{
    if (Application.Current?.MainPage != null)
        await Application.Current.MainPage.DisplayAlert("Cases",
            CaseName, "OK");

    await Shell.Current.GoToAsync(nameof(AreasOfLawResultsPage));
}

当前代码的核心问题是：按钮绑定的ViewModel级命令未接收当前单元格的CaseName参数，导致无法获取对应单元格的值。按以下步骤修改即可解决：

1. 升级命令以接收参数 #

更新ViewModel中的RelayCommand，让它接收string类型的CaseName参数，同时将参数传递到下一页：

[RelayCommand]
public async Task GoToCaseIndex(string caseName)
{
    if (!string.IsNullOrEmpty(caseName) && Application.Current?.MainPage != null)
        await Application.Current.MainPage.DisplayAlert("Cases", caseName, "OK");

    // 转义参数避免特殊字符问题，传递到下一页
    await Shell.Current.GoToAsync($"{nameof(AreasOfLawResultsPage)}?CaseName={Uri.EscapeDataString(caseName)}");
}

[RelayCommand]
public async Task GoToCaseJudgment(string caseName)
{
    if (!string.IsNullOrEmpty(caseName) && Application.Current?.MainPage != null)
        await Application.Current.MainPage.DisplayAlert("Cases", caseName, "OK");

    await Shell.Current.GoToAsync($"{nameof(AreasOfLawResultsPage)}?CaseName={Uri.EscapeDataString(caseName)}");
}

2. 给按钮添加CommandParameter #

在XAML中，给两个按钮绑定CommandParameter，直接关联当前单元格的CaseName：

<Button x:Name="IndexButton" 
        TextColor="White" 
        BackgroundColor="Red"
        FontSize="12" 
        Text="Index" 
        Grid.Column="0" Margin="5,0,5,0" 
        Command="{Binding Source={x:Reference CasesCollectionView}, Path=BindingContext.GoToCaseIndexCommand}"
        CommandParameter="{Binding CaseName}"/>
<Button x:Name="JudgmentButton" 
        TextColor="White" 
        BackgroundColor="Red"
        FontSize="12" 
        Text="Judgment" 
        Grid.Column="1" Margin="5,0,5,0" 
        Command="{Binding Source={x:Reference CasesCollectionView}, Path=BindingContext.GoToCaseJudgmentCommand}"
        CommandParameter="{Binding CaseName}"/>

3. 修复Label绑定错误 #

原XAML中Case Label的绑定引用了自身，会导致绑定失败，改为直接绑定CaseName：

<Label x:Name="Case" 
        TextColor="Red" 
        Text="{Binding CaseName}"
        FontSize="13" 
        FontAttributes="Bold" 
        Padding="0,0,0,10" />

4. 下一页接收参数（可选） #

如果需要在AreasOfLawResultsPage中获取传递的CaseName，可在该页面的ViewModel中添加查询属性：

[QueryProperty(nameof(CaseName), "CaseName")]
public partial class AreasOfLawResultsPageViewModel : ObservableObject
{
    [ObservableProperty]
    private string? caseName;
}

内容的提问来源于stack exchange，提问作者user134935