ViewModel 孩子没有正确刷新？ WPF中的绑定

Question

我有一个视图，里面有另一个视图。我想为他们两个制作 ViewModel。但显然子视图中的绑定无法正常工作，或者我做了错误的绑定，也许。

我已经调试过，每次在父视图模型中选择不同的行时，都会重新创建子视图模型。 但 UI 不会刷新，尽管 UpdateSourceTrigger=PropertyChanged。

如果我在运行应用程序时在 XAML 中编辑绑定，那么它会被刷新（因为绑定可能会重新生成）。

我可以设置 UpdateSourceTrigger=Explicit，但我无法从任何 ViewModel 中调用 UpdateSource。

家长视图：

<UserControl ... DataContext="{Binding ProjectsViewModel, Source={StaticResource ViewModelLocator}}">
    <Grid>
        <poc:AdvancedListView ItemsSource="{Binding Projects}" SelectedObject="{Binding SelectedProject, Mode=TwoWay}"/>
        ...
        <ScrollViewer>
            <StackPanel Orientation="Vertical">
                ...
                <poc:Section SectionName="ATTACHMENTS">
                    <poc:AttachmentsControl DataContext="{Binding AttachmentsViewModel, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" /> // THIS IS BINDING BETWEEN VM
                </poc:Section>
            </StackPanel>
        </ScrollViewer>
    </Grid>
</UserControl>

父视图模型：

public class ProjectsViewModel : BaseViewModel
{
    public ProjectsViewModel(ObservableCollection<Project> projects)
    {
        this.Projects = projects;
    }

    public ObservableCollection<Project> Projects { get; }

    private Project selectedProject;
    public Project SelectedProject
    {
        get { return selectedProject; }
        set
        {
            SetPropertyAndNotify(ref selectedProject, value);
            AttachmentsViewModel = new AttachmentsViewModel(selectedProject.Attachments); // THIS IS CREATION OF CHILD VM
        }
    }

    public AttachmentsViewModel AttachmentsViewModel { get; set; }
}

儿童视图：

<UserControl ... x:Name="attachmentControl">
    <Grid x:Name="mainGrid">
        ...
        <ListView x:Name="attachmentsListView" ItemsSource="{Binding Attachments, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" SelectionMode="Single"> // THIS IS BINDING TO LIST THAT IS NOT WORKING
            <ListView.View>
                <GridView>
                    ...
                </GridView>
            </ListView.View>
        </ListView>
    </Grid>
</UserControl>

儿童视图模型：

public class AttachmentsViewModel : BaseViewModel
{
    public ObservableCollection<Attachment> Attachments { get; set; }

    public AttachmentsViewModel(ObservableCollection<Attachment> attachments)
    {
        Attachments = attachments;
    }

}

我做错了什么或者我理解错了什么概念？

Answer 1

public class ProjectsViewModel : BaseViewModel
{
    public ProjectsViewModel(ObservableCollection<Project> projects)
    {
        this.Projects = projects;
    }

    public ObservableCollection<Project> Projects { get; }

    private Project selectedProject;
    public Project SelectedProject
    {
        get { return selectedProject; }
        set
        {
            SetPropertyAndNotify(ref selectedProject, value);

            // THIS IS CREATION OF CHILD VM
            AttachmentsViewModel = new AttachmentsViewModel(selectedProject.Attachments);         
        }
    }

    private AttachmentsViewModel _attachmentsViewModel;
    public AttachmentsViewModel AttachmentsViewModel
    {
       get => _attachmentsViewModel;
       set => SetPropertyAndNotify(_attachmentsViewModel, value);
    }
}

public class AttachmentsViewModel : BaseViewModel
{
    // This should be a Read Only property
    public ObservableCollection<Attachment> Attachments { get; /* set; */}

    public AttachmentsViewModel(ObservableCollection<Attachment> attachments)
    {
        Attachments = attachments;
    }
}

其他建议：向属性设置器添加额外的逻辑 - 不好。 当然，在 BaseViewModel 实现中，有机会以不同的方式设置属性之间的依赖关系。