c# - 在 MVVM 中的窗口之间传递 DataContext

Question

在我的主窗口onClick上

AddNoticeAboutWrongCity addNoticeAboutWrongCity = new AddNoticeAboutWrongCity();
addNoticeAboutWrongCity.DataContext = ((VerificationViewModule)this.DataContext).WrongCityNotice;
addNoticeAboutWrongCity.ShowDialog();

弹出窗口有很多文本框和两个按钮

删除对象:

this.DataContext = null;

第二个选项“Save edited notice”不可用，因为主窗口上用户情感数据上下文的每次更改，这是设计部门的要求:)

我不知道为什么第一个选项(它的“实现”不起作用。

第二种解释:

在 ParentWindow 上我有通知列表，我可以单击 EditSelectedNotice。

在 EditNoticeWindow 上我可以编辑通知或删除通知。

Editinig 有效(关闭 EditNoticeWindow 后，我在 ParentWindow 上看到更改的通知)，但删除没有(通知仍在集合中 - 在控件上和 this.DataContext 中)

我的 View 模型:

class VerificationViewModule
    {
        public ObservableCollection<ReporterNotice> ReporterNotices { get; set; }

        public ReporterNotice OtherNotice
        {
            get
            {
                return ReporterNotices.Where(n => n.Type == ReporterNoticeType.Other).FirstOrDefault();
            }
        }
        public ReporterNotice DuplicateNotice
        {
            get
            {
                return ReporterNotices.Where(n => n.Type == ReporterNoticeType.Duplicate).FirstOrDefault();
            }
        }
        public ReporterNotice WrongCityNotice
        {
            get
            {
                return ReporterNotices.Where(n => n.Type == ReporterNoticeType.WrongCity).FirstOrDefault();
            }
            set { if(value==null)
            {
                ReporterNotices.Remove(ReporterNotices.Where(n => n.Type == ReporterNoticeType.WrongCity).First());
            }
            else
            {
                if (ReporterNotices.Where(n => n.Type == ReporterNoticeType.WrongCity).FirstOrDefault()==null)//there is always only max one instance of this type of notice
                {
                    ReporterNotices.Add(value);
                }
                else
                {
                    var c = ReporterNotices.Where(n => n.Type == ReporterNoticeType.WrongCity).First();
                    c = value;

                }
            }}
        }

         public VerificationViewModule()
        {
            ObservableCollection<ReporterNotice> loadedReporterNotices = new ObservableCollection<ReporterNotice>();
            loadedReporterNotices.Add(new ReporterNotice() { Content = "Dublic", Type = ReporterNoticeType.WrongCity });
            loadedReporterNotices.Add(new ReporterNotice() { Content = "Hilton", Type = ReporterNoticeType.Duplicate });
            loadedReporterNotices.Add(new ReporterNotice() { Content = "Another notice", Type = ReporterNoticeType.Other });
            ReporterNotices = loadedReporterNotices;
        }


    }

Answer 1

您可以尝试以下操作。实现调解器以显示窗口，并确保为主窗口和编辑窗口都使用 DataContext 的 View 模型。重要的是要告诉主视图模型对象正在被删除。这是通过回调和路由完成的，通过 EditNoticeViewModel 上的命令

    //This viewmodel is on the main windows datacontext
public class ParentViewModel
{
    private readonly IWindowMediator _mediator;
    public ParentViewModel(IWindowMediator mediator)
    {
        _mediator = mediator;
    }

    public ObservableCollection<Notice> Notices { get; private set; } //bound to list in xaml

    public void OpenNotice(Notice notice)
    {
        //open the window using the Mediator pattern rather than a new window directly

        _mediator.Open(new EditNoticeViewModel(notice, DeleteNotice));
    }

    private void DeleteNotice(Notice notice)
    {
        //This will remove it from the main window list
        Notices.Remove(notice);
    }
}

//view model for EditNoticeWindow
public class EditNoticeViewModel
{
    public EditNoticeViewModel(Action<Notice> deleteCallback, Notice notice)
    {
        Model = notice;

        DeleteCommand = new DelegateCommand((a) => deleteCallback(Model));
    }

    //Bind in xaml to the Command of a button
    DelegateCommand DeleteCommand { get; private set; }

    //bound to the controls in the xaml.
    public Notice Model { get; private set; }
}

//This is a basic interface, you can elaborate as needed
//but it handles the opening of windows. Attach the view model
//to the data context of the window.
public interface IWindowMediator
{
    void Open<T>(T viewModel);
}

根据实现，您可能希望在按下删除按钮时关闭 View 。您可以通过实现类似 here 中描述的内容来做到这一点关于 WorkspaceViewModel