Question

我已经搜索了一个解决方案的高低，但我似乎没有找到它的底部。像网上的很多帖子我似乎没有让我的itemPropertyChanged工作。编辑集合中的项目时不会触发。为什么。

有点长，但这是我放在一起的一个例子。

我有一个customerViewModel，其中包含OrderViewModel的集合在数据网格中编辑订单时，事件不会触发。

我已经实现了以下功能，但只在加载时才会被解雇。好像它不是同一个东西的集合......

INotifyPropertyChanged inpc = OrderViewModels;
inpc.PropertyChanged += OnItemPropertyChanged;

有什么建议吗？这让我很生气

模型

public class Order
{
    public int Id { get; set; }
    public string Description { get; set; }
    public int CustomerId{ get; set; }
}

public class Customer
{
    public Customer()
    {
        Orders=new ObservableCollection<Order>();
    }

    public int Id { get; set; }
    public string Name { get; set; }
    public string Surname{ get; set;}
    public ObservableCollection<Order> Orders{ get; set;}

}

的ViewModels

public class CustomerViewModel : ViewModelBase
{
    private Customer _customerModel;

    public CustomerViewModel(Customer customerModel)
    {
        _customerModel = customerModel;
        _orderViewModels = new ObservableCollection<OrderViewModel>();
        OrderViewModels.CollectionChanged += OnOrdersCollectionChanged;
        INotifyPropertyChanged inpc = OrderViewModels;
        inpc.PropertyChanged += OnItemPropertyChanged; 

    }

    private void OnItemPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        //not firing!!!!!!!!!!!!!!!!!!!!!!!!!
    }

    void OnOrdersCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        switch (e.Action)
        {
            case NotifyCollectionChangedAction.Add:
                _customerModel.Orders.Insert(e.NewStartingIndex, ((OrderViewModel)e.NewItems[0]).OrderModel);
                break;
            case NotifyCollectionChangedAction.Remove:
                _customerModel.Orders.RemoveAt(e.OldStartingIndex);
                break;
            case NotifyCollectionChangedAction.Replace:
                _customerModel.Orders[e.OldStartingIndex] = ((OrderViewModel)e.NewItems[0]).OrderModel;
                break;
            case NotifyCollectionChangedAction.Move:
                _customerModel.Orders.Move(e.OldStartingIndex, e.NewStartingIndex);
                break;

            default:
                throw new ArgumentOutOfRangeException();
        }
    }

    public int Id
    {
        get { return _customerModel.Id; }
        set
        {
            _customerModel.Id = value;
            OnPropertyChanged("Id");
        }
    }

    public string Name
    {
        get { return _customerModel.Name; }
        set
        {
            _customerModel.Name = value;
            OnPropertyChanged("Name");
        }
    }

    public string Surname
    {
        get { return _customerModel.Surname; }
        set
        {
            _customerModel.Surname = value;
            OnPropertyChanged("Surname");
        }
    }
    public Customer CustomerModel
    {
        get { return _customerModel; }
        set
        {
            _customerModel = value;
            OnPropertyChanged("");
        }
    }

    private ObservableCollection<OrderViewModel> _orderViewModels;

    public ObservableCollection<OrderViewModel> OrderViewModels
    {
        get { return _orderViewModels; }
        set
        {
            _orderViewModels = value;
            OnPropertyChanged("OrderViewModels");
        }
    }
}

public class OrderViewModel:ViewModelBase
{
    private Order _orderModel;

    public OrderViewModel(Order orderModel)
    {
        _orderModel = orderModel;
    }

    public int Id
    {
        get { return _orderModel.Id; }
        set
        {
            _orderModel.Id = value;
            OnPropertyChanged("Id");
        }
    }
    public int CustomerId
    {
        get { return _orderModel.CustomerId; }
        set
        {
            _orderModel.CustomerId = value;
            OnPropertyChanged("CustomerId");
        }
    }
    public string Description 
    {
        get { return _orderModel.Description; }
        set
        {
            _orderModel.Description = value;
            OnPropertyChanged("Description");
        }
    }

    public Order OrderModel
    {
        get { return _orderModel; }
        set
        {
            _orderModel = value;
            OnPropertyChanged("");
        }
    }
}

存储库

public class OrderRepository
{
    public static ObservableCollection<Order> GetOrders(int customerId)
    {
        return new ObservableCollection<Order>
               {
                   new Order {Id = 1, CustomerId=1, Description = "MotherBoard"},
                   new Order {Id = 2, CustomerId=1,Description = "Video Card"},
                   new Order {Id = 3, CustomerId=1,Description = "TV"},
                   new Order {Id = 4, CustomerId=1, Description = "Video Recorder"},
                   new Order {Id = 5, CustomerId=1,Description = "Speakers"},
                   new Order {Id = 6, CustomerId=1,Description = "Computer"}
               };
    }
}

查看

public partial class OrdersView
{
    public OrdersView()
    {
        InitializeComponent();

        if (!DesignerProperties.GetIsInDesignMode(this))
        {
            var customerVm =
                new CustomerViewModel(new Customer
                                          {
                                              Id = 1,
                                              Name = "Jo",
                                              Surname = "Bloggs"
                                          });

            var orders = OrderRepository.GetOrders(1);
            foreach (var orderModel in orders)
            {
                customerVm.OrderViewModels.Add(new OrderViewModel(orderModel));
            }
            DataContext = customerVm;
        }
    }
}

的Xaml

<Grid>
    <DataGrid AutoGenerateColumns="False" AlternationCount="2" ItemsSource="{Binding Path=OrderViewModels}">
        <DataGrid.Columns>
            <DataGridTextColumn Binding="{Binding Id}" Header="Id"/>
            <DataGridTextColumn Binding="{Binding CustomerId}" Header="Customer Id"/>
            <DataGridTextColumn Header="Description" Binding="{Binding Description,UpdateSourceTrigger=PropertyChanged}"/>
        </DataGrid.Columns>
    </DataGrid>
</Grid>

Answer 1

    INotifyPropertyChanged inpc = OrderViewModels;
    inpc.PropertyChanged += OnItemPropertyChanged;

当ObservableCollection<T>上的任何属性发生变化时，该代码会通知您，当ObservableCollection<T>中的项目的属性发生变化时，。例如，添加或删除OrderViewModel时应调用您的处理程序，因为Count上的ObservableCollection<OrderViewModel>属性会发生变化。

没有任何内容在PropertyChanged内传播OrderViewModel事件，并将它们聚合为单个事件。当我想这样做时，我使用了一个名为ItemObservableCollection的课程：

public sealed class ItemObservableCollection<T> : ObservableCollection<T> where T : INotifyPropertyChanged { public event EventHandler<ItemPropertyChangedEventArgs<T>> ItemPropertyChanged; protected override void InsertItem(int index, T item) { base.InsertItem(index, item); item.PropertyChanged += item_PropertyChanged; } protected override void RemoveItem(int index) { var item= this[index]; base.RemoveItem(index); item.PropertyChanged -= item_PropertyChanged; } protected override void ClearItems() { foreach (var item in this) { item.PropertyChanged -= item_PropertyChanged; } base.ClearItems(); } protected override void SetItem(int index, T item) { var oldItem = this[index]; oldItem.PropertyChanged -= item_PropertyChanged; base.SetItem(index, item); item.PropertyChanged += item_PropertyChanged; } private void item_PropertyChanged(object sender, PropertyChangedEventArgs e) { OnItemPropertyChanged((T)sender, e.PropertyName); } private void OnItemPropertyChanged(T item, string propertyName) { var handler = this.ItemPropertyChanged; if (handler != null) { handler(this, new ItemPropertyChangedEventArgs<T>(item, propertyName)); } } } public sealed class ItemPropertyChangedEventArgs<T> : EventArgs { private readonly T _item; private readonly string _propertyName; public ItemPropertyChangedEventArgs(T item, string propertyName) { _item = item; _propertyName = propertyName; } public T Item { get { return _item; } } public string PropertyName { get { return _propertyName; } } }

我可以这样使用它：

var orders = new ItemObservableCollection<OrderViewModel>(); orders.CollectionChanged += OnOrdersChanged; orders.ItemPropertyChanged += OnOrderChanged;

Answer 2

System.ComponentModel.BindingList<Type>提供与ObservableCollection<Type>相同的功能，并正确处理 PropertyChanged 事件。

祝你好运

ItemPropertyChanged无法处理observableCollection.Why？

2 个答案: