ItemPropertyChanged无法在observableCollection上使用。为什么？ [英] ItemPropertyChanged not working on observableCollection.Why?
问题描述
我一直在寻找一个高低的解决方案，但是我似乎并没有深入了解它。
就像网上的许多帖子一样，我似乎没有使我的itemPropertyChanged工作。
编辑集合中的项目时不会触发。
I have searched high and low for a solution but I dont seem to get to the bottom of it. Like many posts on the net I dont seem to make my itemPropertyChanged work. It does not fire when editing an item in the collection.Why.
有点冗长，但这是我整理的一个示例。
a bit lenghty but this is an example I have put together.
我有一个customerViewModel，其中包含在不触发事件的datagrid中编辑订单时包含OrderViewModels
的集合。
I have a customerViewModel that contains a Collections of OrderViewModels when editing the order in the datagrid the event does not fire.
我已经实现了以下内容，但是只有在加载时才进行编辑。
好像它不是同一个东西的集合...
I have implemented the following but never gets fired when editing only when loading. As if it's not the same collection of something...
INotifyPropertyChanged inpc = OrderViewModels;
inpc.PropertyChanged += OnItemPropertyChanged;
有任何建议吗？这让我发疯了
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;}
}
ViewModels
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;
}
}
}
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>
推荐答案
INotifyPropertyChanged inpc = OrderViewModels;
inpc.PropertyChanged += OnItemPropertyChanged;
该代码将在 ObservableCollection< T> 更改，当 ObservableCollection< T> 中的项的属性更改时，不会更改。。例如，添加或删除 OrderViewModel 时应调用处理程序，因为 Count 属性将在 ObservableCollection< OrderViewModel> 。
That code will notify you when any property on the ObservableCollection<T> changes, not when items in the ObservableCollection<T> have their properties changed. For example, your handler should be called when you add or remove an OrderViewModel because the Count property will change on the ObservableCollection<OrderViewModel>.
什么都没有传播 PropertyChanged OrderViewModel s中的事件，并将它们汇总为一个事件。当我想执行此操作时，我使用名为 ItemObservableCollection 的类：
Nothing is propagating the PropertyChanged event inside OrderViewModels and aggregating them into a single event for you. I use a class I called ItemObservableCollection when I want to do this:
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;
这篇关于ItemPropertyChanged无法在observableCollection上使用。为什么？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
