c# - ObservableCollection 没有注意到其中的项目何时更改（即使使用 INotifyPropertyChanged）

Question

有谁知道为什么这段代码不起作用：

public class CollectionViewModel : ViewModelBase {  
    public ObservableCollection<EntityViewModel> ContentList
    {
        get { return _contentList; }
        set 
        { 
            _contentList = value; 
            RaisePropertyChanged("ContentList"); 
            //I want to be notified here when something changes..?
            //debugger doesn't stop here when IsRowChecked is toggled
        }
     }
}

public class EntityViewModel : ViewModelBase
{

    private bool _isRowChecked;

    public bool IsRowChecked
    {
        get { return _isRowChecked; }
        set { _isRowChecked = value; RaisePropertyChanged("IsRowChecked"); }
    }
}

ViewModelBase包含RaisePropertyChanged等的所有内容，并且它适用于除此问题之外的所有其他内容..

score 190 · Accepted Answer

这是一个插入类，它是 ObservableCollection 的子类，当列表项的属性发生更改时，它实际上会引发一个 Reset 操作。它强制执行所有项目INotifyPropertyChanged。

这里的好处是您可以将数据绑定到此类，并且您的所有绑定都将随着项目属性的更改而更新。

public sealed class TrulyObservableCollection<T> : ObservableCollection<T>
    where T : INotifyPropertyChanged
{
    public TrulyObservableCollection()
    {
        CollectionChanged += FullObservableCollectionCollectionChanged;
    }

    public TrulyObservableCollection(IEnumerable<T> pItems) : this()
    {
        foreach (var item in pItems)
        {
            this.Add(item);
        }
    }

    private void FullObservableCollectionCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.NewItems != null)
        {
            foreach (Object item in e.NewItems)
            {
                ((INotifyPropertyChanged)item).PropertyChanged += ItemPropertyChanged;
            }
        }
        if (e.OldItems != null)
        {
            foreach (Object item in e.OldItems)
            {
                ((INotifyPropertyChanged)item).PropertyChanged -= ItemPropertyChanged;
            }
        }
    }

    private void ItemPropertyChanged(object sender, PropertyChangedEventArgs e)
    {            
        NotifyCollectionChangedEventArgs args = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace, sender, sender, IndexOf((T)sender));
        OnCollectionChanged(args);
    }
}

score 131 · Accepted Answer

当您更改集合内的值时，不会调用 ContentList 的 Set 方法，而是应该注意CollectionChanged事件的触发。

public class CollectionViewModel : ViewModelBase
{          
    public ObservableCollection<EntityViewModel> ContentList
    {
        get { return _contentList; }
    }

    public CollectionViewModel()
    {
         _contentList = new ObservableCollection<EntityViewModel>();
         _contentList.CollectionChanged += ContentCollectionChanged;
    }

    public void ContentCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        //This will get called when the collection is changed
    }
}

好的，这是我今天两次被 MSDN 文档错误所困扰。在我给你的链接中，它说：

在添加、删除、更改、移动项目或刷新整个列表时发生。

但它实际上不会在更改项目时触发。我想你需要一个更暴力的方法：

public class CollectionViewModel : ViewModelBase
{          
    public ObservableCollection<EntityViewModel> ContentList
    {
        get { return _contentList; }
    }

    public CollectionViewModel()
    {
         _contentList = new ObservableCollection<EntityViewModel>();
         _contentList.CollectionChanged += ContentCollectionChanged;
    }

    public void ContentCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        if (e.Action == NotifyCollectionChangedAction.Remove)
        {
            foreach(EntityViewModel item in e.OldItems)
            {
                //Removed items
                item.PropertyChanged -= EntityViewModelPropertyChanged;
            }
        }
        else if (e.Action == NotifyCollectionChangedAction.Add)
        {
            foreach(EntityViewModel item in e.NewItems)
            {
                //Added items
                item.PropertyChanged += EntityViewModelPropertyChanged;
            }     
        }       
    }

    public void EntityViewModelPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        //This will get called when the property of an object inside the collection changes
    }
}

如果你需要这个很多，你可能想要子类化你自己的子类ObservableCollection，CollectionChanged当成员PropertyChanged自动触发其事件时触发事件（就像它在文档中所说的那样......）

score 35 · Accepted Answer

我已经将我希望是一个非常强大的解决方案放在一起，包括其他答案中的一些技术。这是一个派生自的新类ObservableCollection<>，我称之为FullyObservableCollection<>

它具有以下特点：

它添加了一个新事件，ItemPropertyChanged. 我故意将其与现有的分开CollectionChanged：
- 帮助向后兼容。
- 因此，可以在ItemPropertyChangedEventArgs随附的新版本中提供更多相关细节：原始版本PropertyChangedEventArgs和集合中的索引。
它复制了所有的构造函数ObservableCollection<>。
它正确处理正在重置的列表 ( ObservableCollection<>.Clear())，避免了可能的内存泄漏。
它覆盖了基类的OnCollectionChanged()，而不是对事件的资源更密集的订阅CollectionChanged。

代码

完整的.cs文件如下。请注意，已经使用了 C# 6 的一些特性，但向后移植它应该相当简单：

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;

namespace Utilities
{
    public class FullyObservableCollection<T> : ObservableCollection<T>
        where T : INotifyPropertyChanged
    {
        /// <summary>
        /// Occurs when a property is changed within an item.
        /// </summary>
        public event EventHandler<ItemPropertyChangedEventArgs> ItemPropertyChanged;

        public FullyObservableCollection() : base()
        { }

        public FullyObservableCollection(List<T> list) : base(list)
        {
            ObserveAll();
        }

        public FullyObservableCollection(IEnumerable<T> enumerable) : base(enumerable)
        {
            ObserveAll();
        }

        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            if (e.Action == NotifyCollectionChangedAction.Remove ||
                e.Action == NotifyCollectionChangedAction.Replace)
            {
                foreach (T item in e.OldItems)
                    item.PropertyChanged -= ChildPropertyChanged;
            }

            if (e.Action == NotifyCollectionChangedAction.Add ||
                e.Action == NotifyCollectionChangedAction.Replace)
            {
                foreach (T item in e.NewItems)
                    item.PropertyChanged += ChildPropertyChanged;
            }

            base.OnCollectionChanged(e);
        }

        protected void OnItemPropertyChanged(ItemPropertyChangedEventArgs e)
        {
            ItemPropertyChanged?.Invoke(this, e);
        }

        protected void OnItemPropertyChanged(int index, PropertyChangedEventArgs e)
        {
            OnItemPropertyChanged(new ItemPropertyChangedEventArgs(index, e));
        }

        protected override void ClearItems()
        {
            foreach (T item in Items)
                item.PropertyChanged -= ChildPropertyChanged;

            base.ClearItems();
        }

        private void ObserveAll()
        {
            foreach (T item in Items)
                item.PropertyChanged += ChildPropertyChanged;
        }

        private void ChildPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            T typedSender = (T)sender;
            int i = Items.IndexOf(typedSender);

            if (i < 0)
                throw new ArgumentException("Received property notification from item not in collection");

            OnItemPropertyChanged(i, e);
        }
    }

    /// <summary>
    /// Provides data for the <see cref="FullyObservableCollection{T}.ItemPropertyChanged"/> event.
    /// </summary>
    public class ItemPropertyChangedEventArgs : PropertyChangedEventArgs
    {
        /// <summary>
        /// Gets the index in the collection for which the property change has occurred.
        /// </summary>
        /// <value>
        /// Index in parent collection.
        /// </value>
        public int CollectionIndex { get; }

        /// <summary>
        /// Initializes a new instance of the <see cref="ItemPropertyChangedEventArgs"/> class.
        /// </summary>
        /// <param name="index">The index in the collection of changed item.</param>
        /// <param name="name">The name of the property that changed.</param>
        public ItemPropertyChangedEventArgs(int index, string name) : base(name)
        {
            CollectionIndex = index;
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="ItemPropertyChangedEventArgs"/> class.
        /// </summary>
        /// <param name="index">The index.</param>
        /// <param name="args">The <see cref="PropertyChangedEventArgs"/> instance containing the event data.</param>
        public ItemPropertyChangedEventArgs(int index, PropertyChangedEventArgs args) : this(index, args.PropertyName)
        { }
    }
}

NUnit 测试

因此，您可以检查您可能做出的更改（并首先查看我测试的内容！），我还包含了我的 NUnit 测试类。显然，以下代码并非仅用于FullyObservableCollection<T>您的项目中所必需的。

NB测试类使用BindableBasefrom PRISM 来实现INotifyPropertyChanged。主代码不依赖于 PRISM。

using NUnit.Framework;
using Utilities;
using Microsoft.Practices.Prism.Mvvm;
using System.Collections.Specialized;
using System.Collections.Generic;

namespace Test_Utilities
{
    [TestFixture]
    public class Test_FullyObservableCollection : AssertionHelper
    {
        public class NotifyingTestClass : BindableBase
        {
            public int Id
            {
                get { return _Id; }
                set { SetProperty(ref _Id, value); }
            }
            private int _Id;

            public string Name
            {
                get { return _Name; }
                set { SetProperty(ref _Name, value); }
            }
            private string _Name;

        }

        FullyObservableCollection<NotifyingTestClass> TestCollection;
        NotifyingTestClass Fred;
        NotifyingTestClass Betty;
        List<NotifyCollectionChangedEventArgs> CollectionEventList;
        List<ItemPropertyChangedEventArgs> ItemEventList;

        [SetUp]
        public void Init()
        {
            Fred = new NotifyingTestClass() { Id = 1, Name = "Fred" };
            Betty = new NotifyingTestClass() { Id = 4, Name = "Betty" };

            TestCollection = new FullyObservableCollection<NotifyingTestClass>()
                {
                    Fred,
                    new NotifyingTestClass() {Id = 2, Name = "Barney" },
                    new NotifyingTestClass() {Id = 3, Name = "Wilma" }
                };

            CollectionEventList = new List<NotifyCollectionChangedEventArgs>();
            ItemEventList = new List<ItemPropertyChangedEventArgs>();
            TestCollection.CollectionChanged += (o, e) => CollectionEventList.Add(e);
            TestCollection.ItemPropertyChanged += (o, e) => ItemEventList.Add(e);
        }

        // Change existing member property: just ItemPropertyChanged(IPC) should fire
        [Test]
        public void DetectMemberPropertyChange()
        {
            TestCollection[0].Id = 7;

            Expect(CollectionEventList.Count, Is.EqualTo(0));

            Expect(ItemEventList.Count, Is.EqualTo(1), "IPC count");
            Expect(ItemEventList[0].PropertyName, Is.EqualTo(nameof(Fred.Id)), "Field Name");
            Expect(ItemEventList[0].CollectionIndex, Is.EqualTo(0), "Collection Index");
        }


        // Add new member, change property: CollectionPropertyChanged (CPC) and IPC should fire
        [Test]
        public void DetectNewMemberPropertyChange()
        {
            TestCollection.Add(Betty);

            Expect(TestCollection.Count, Is.EqualTo(4));
            Expect(TestCollection[3].Name, Is.EqualTo("Betty"));

            Expect(ItemEventList.Count, Is.EqualTo(0), "Item Event count");

            Expect(CollectionEventList.Count, Is.EqualTo(1), "Collection Event count");
            Expect(CollectionEventList[0].Action, Is.EqualTo(NotifyCollectionChangedAction.Add), "Action (add)");
            Expect(CollectionEventList[0].OldItems, Is.Null, "OldItems count");
            Expect(CollectionEventList[0].NewItems.Count, Is.EqualTo(1), "NewItems count");
            Expect(CollectionEventList[0].NewItems[0], Is.EqualTo(Betty), "NewItems[0] dereference");

            CollectionEventList.Clear();      // Empty for next operation
            ItemEventList.Clear();

            TestCollection[3].Id = 7;
            Expect(CollectionEventList.Count, Is.EqualTo(0), "Collection Event count");

            Expect(ItemEventList.Count, Is.EqualTo(1), "Item Event count");
            Expect(TestCollection[ItemEventList[0].CollectionIndex], Is.EqualTo(Betty), "Collection Index dereference");
        }


        // Remove member, change property: CPC should fire for removel, neither CPC nor IPC should fire for change
        [Test]
        public void CeaseListentingWhenMemberRemoved()
        {
            TestCollection.Remove(Fred);

            Expect(TestCollection.Count, Is.EqualTo(2));
            Expect(TestCollection.IndexOf(Fred), Is.Negative);

            Expect(ItemEventList.Count, Is.EqualTo(0), "Item Event count (pre change)");

            Expect(CollectionEventList.Count, Is.EqualTo(1), "Collection Event count (pre change)");
            Expect(CollectionEventList[0].Action, Is.EqualTo(NotifyCollectionChangedAction.Remove), "Action (remove)");
            Expect(CollectionEventList[0].OldItems.Count, Is.EqualTo(1), "OldItems count");
            Expect(CollectionEventList[0].NewItems, Is.Null, "NewItems count");
            Expect(CollectionEventList[0].OldItems[0], Is.EqualTo(Fred), "OldItems[0] dereference");

            CollectionEventList.Clear();      // Empty for next operation
            ItemEventList.Clear();

            Fred.Id = 7;
            Expect(CollectionEventList.Count, Is.EqualTo(0), "Collection Event count (post change)");
            Expect(ItemEventList.Count, Is.EqualTo(0), "Item Event count (post change)");
        }


        // Move member in list, change property: CPC should fire for move, IPC should fire for change
        [Test]
        public void MoveMember()
        {
            TestCollection.Move(0, 1);

            Expect(TestCollection.Count, Is.EqualTo(3));
            Expect(TestCollection.IndexOf(Fred), Is.GreaterThan(0));

            Expect(ItemEventList.Count, Is.EqualTo(0), "Item Event count (pre change)");

            Expect(CollectionEventList.Count, Is.EqualTo(1), "Collection Event count (pre change)");
            Expect(CollectionEventList[0].Action, Is.EqualTo(NotifyCollectionChangedAction.Move), "Action (move)");
            Expect(CollectionEventList[0].OldItems.Count, Is.EqualTo(1), "OldItems count");
            Expect(CollectionEventList[0].NewItems.Count, Is.EqualTo(1), "NewItems count");
            Expect(CollectionEventList[0].OldItems[0], Is.EqualTo(Fred), "OldItems[0] dereference");
            Expect(CollectionEventList[0].NewItems[0], Is.EqualTo(Fred), "NewItems[0] dereference");

            CollectionEventList.Clear();      // Empty for next operation
            ItemEventList.Clear();

            Fred.Id = 7;
            Expect(CollectionEventList.Count, Is.EqualTo(0), "Collection Event count (post change)");

            Expect(ItemEventList.Count, Is.EqualTo(1), "Item Event count (post change)");
            Expect(TestCollection[ItemEventList[0].CollectionIndex], Is.EqualTo(Fred), "Collection Index dereference");
        }


        // Clear list, chnage property: only CPC should fire for clear and neither for property change
        [Test]
        public void ClearList()
        {
            TestCollection.Clear();

            Expect(TestCollection.Count, Is.EqualTo(0));

            Expect(ItemEventList.Count, Is.EqualTo(0), "Item Event count (pre change)");

            Expect(CollectionEventList.Count, Is.EqualTo(1), "Collection Event count (pre change)");
            Expect(CollectionEventList[0].Action, Is.EqualTo(NotifyCollectionChangedAction.Reset), "Action (reset)");
            Expect(CollectionEventList[0].OldItems, Is.Null, "OldItems count");
            Expect(CollectionEventList[0].NewItems, Is.Null, "NewItems count");

            CollectionEventList.Clear();      // Empty for next operation
            ItemEventList.Clear();

            Fred.Id = 7;
            Expect(CollectionEventList.Count, Is.EqualTo(0), "Collection Event count (post change)");
            Expect(ItemEventList.Count, Is.EqualTo(0), "Item Event count (post change)");
        }
    }
}

score 21 · Accepted Answer

这使用了上述想法，但使其成为派生的“更敏感”的集合：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.Collections;

namespace somethingelse
{
    public class ObservableCollectionEx<T> : ObservableCollection<T> where T : INotifyPropertyChanged
    {
        // this collection also reacts to changes in its components' properties

        public ObservableCollectionEx() : base()
        {
            this.CollectionChanged +=new System.Collections.Specialized.NotifyCollectionChangedEventHandler(ObservableCollectionEx_CollectionChanged);
        }

        void ObservableCollectionEx_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {
            if (e.Action == NotifyCollectionChangedAction.Remove)
            {
                foreach(T item in e.OldItems)
                {
                    //Removed items
                    item.PropertyChanged -= EntityViewModelPropertyChanged;
                }
            }
            else if (e.Action == NotifyCollectionChangedAction.Add)
            {
                foreach(T item in e.NewItems)
                {
                    //Added items
                    item.PropertyChanged += EntityViewModelPropertyChanged;
                }     
            }       
        }

        public void EntityViewModelPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            //This will get called when the property of an object inside the collection changes - note you must make it a 'reset' - I don't know, why
            NotifyCollectionChangedEventArgs args = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset);
            OnCollectionChanged(args);
        }
    }
}

score 16 · Accepted Answer

ObservableCollection 不会将单个项目更改作为 CollectionChanged 事件传播。您将需要订阅每个事件并手动转发它，或者您可以查看BindingList[T]类，它会为您执行此操作。

score 7 · Accepted Answer

添加到 TruelyObservableCollection 事件“ItemPropertyChanged”：

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel; // ObservableCollection
using System.ComponentModel; // INotifyPropertyChanged
using System.Collections.Specialized; // NotifyCollectionChangedEventHandler
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ObservableCollectionTest
{
    class Program
    {
        static void Main(string[] args)
        {
            // ATTN: Please note it's a "TrulyObservableCollection" that's instantiated. Otherwise, "Trades[0].Qty = 999" will NOT trigger event handler "Trades_CollectionChanged" in main.
            // REF: http://stackoverflow.com/questions/8490533/notify-observablecollection-when-item-changes
            TrulyObservableCollection<Trade> Trades = new TrulyObservableCollection<Trade>();
            Trades.Add(new Trade { Symbol = "APPL", Qty = 123 });
            Trades.Add(new Trade { Symbol = "IBM", Qty = 456});
            Trades.Add(new Trade { Symbol = "CSCO", Qty = 789 });

            Trades.CollectionChanged += Trades_CollectionChanged;
            Trades.ItemPropertyChanged += PropertyChangedHandler;
            Trades.RemoveAt(2);

            Trades[0].Qty = 999;

            Console.WriteLine("Hit any key to exit");
            Console.ReadLine();

            return;
        }

        static void PropertyChangedHandler(object sender, PropertyChangedEventArgs e)
        {
            Console.WriteLine(DateTime.Now.ToString() + ", Property changed: " + e.PropertyName + ", Symbol: " + ((Trade) sender).Symbol + ", Qty: " + ((Trade) sender).Qty);
            return;
        }

        static void Trades_CollectionChanged(object sender, EventArgs e)
        {
            Console.WriteLine(DateTime.Now.ToString() + ", Collection changed");
            return;
        }
    }

    #region TrulyObservableCollection
    public class TrulyObservableCollection<T> : ObservableCollection<T>
        where T : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler ItemPropertyChanged;

        public TrulyObservableCollection()
            : base()
        {
            CollectionChanged += new NotifyCollectionChangedEventHandler(TrulyObservableCollection_CollectionChanged);
        }

        void TrulyObservableCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            if (e.NewItems != null)
            {
                foreach (Object item in e.NewItems)
                {
                    (item as INotifyPropertyChanged).PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
                }
            }
            if (e.OldItems != null)
            {
                foreach (Object item in e.OldItems)
                {
                    (item as INotifyPropertyChanged).PropertyChanged -= new PropertyChangedEventHandler(item_PropertyChanged);
                }
            }
        }

        void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            NotifyCollectionChangedEventArgs a = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset);
            OnCollectionChanged(a);

            if (ItemPropertyChanged != null)
            {
                ItemPropertyChanged(sender, e);
            }
        }
    }
    #endregion

    #region Sample entity
    class Trade : INotifyPropertyChanged
    {
        protected string _Symbol;
        protected int _Qty = 0;
        protected DateTime _OrderPlaced = DateTime.Now;

        public DateTime OrderPlaced
        {
            get { return _OrderPlaced; }
        }

        public string Symbol
        {
            get
            {
                return _Symbol;
            }
            set
            {
                _Symbol = value;
                NotifyPropertyChanged("Symbol");
            }
        }

        public int Qty
        {
            get
            {
                return _Qty;
            }
            set
            {
                _Qty = value;
                NotifyPropertyChanged("Qty");
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        private void NotifyPropertyChanged(String propertyName = "")
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }
    }
#endregion
}

score 6 · Accepted Answer

我使用 Jack Kenyons 的答案来实现我自己的 OC，但我想指出我必须进行的一项更改才能使其正常工作。代替：

    if (e.Action == NotifyCollectionChangedAction.Remove)
    {
        foreach(T item in e.NewItems)
        {
            //Removed items
            item.PropertyChanged -= EntityViewModelPropertyChanged;
        }
    }

我用这个：

    if (e.Action == NotifyCollectionChangedAction.Remove)
    {
        foreach(T item in e.OldItems)
        {
            //Removed items
            item.PropertyChanged -= EntityViewModelPropertyChanged;
        }
    }

如果操作是 .Remove，“e.NewItems”似乎会产生 null。

score 6 · Accepted Answer

只需在这个主题上加上我的 2 美分。感觉 TrulyObservableCollection 需要使用 ObservableCollection 找到的另外两个构造函数：

public TrulyObservableCollection()
        : base()
    {
        HookupCollectionChangedEvent();
    }

    public TrulyObservableCollection(IEnumerable<T> collection)
        : base(collection)
    {
        foreach (T item in collection)
            item.PropertyChanged += ItemPropertyChanged;

        HookupCollectionChangedEvent();
    }

    public TrulyObservableCollection(List<T> list)
        : base(list)
    {
        list.ForEach(item => item.PropertyChanged += ItemPropertyChanged);

        HookupCollectionChangedEvent();
    }

    private void HookupCollectionChangedEvent()
    {
        CollectionChanged += new NotifyCollectionChangedEventHandler(TrulyObservableCollectionChanged);
    }

score 6 · Accepted Answer

如果我知道 ObservableCollection 仅在我们添加/删除或移动集合中的项目时才发生事件。当我们简单地更新集合项目集合中的某些属性时，不要发出信号，并且 UI 将不会更新。

您可以在 Model 类中简单地实现INotifyPropertyChange。并且当我们更新集合项中的某些属性时，它会自动更新 UI。

public class Model:INotifyPropertyChange
{
//...
}

然后

public ObservableCollection<Model> {get; set;}

在我的情况下，我使用 ListView 来绑定这个集合，并在 ItemTemplate 中设置绑定到模型属性，它工作得很好。

这是一些片段

视窗 XAML：

<Window.DataContext>
    <local:ViewModel/>
</Window.DataContext>
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition/>
        <RowDefinition/>
    </Grid.RowDefinitions>
    <ListView 
        Margin="10"
        BorderBrush="Black"
        HorizontalAlignment="Center"
        SelectedItem="{Binding SelectedPerson}"
        ItemsSource="{Binding Persons}">
        <ListView.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Horizontal">
                    <Label Content="{Binding Name}"/>
                    <Label Content="-"/>
                    <Label Content="{Binding Age}"/>
                </StackPanel>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
    <Grid 
        Grid.Row="1"
        VerticalAlignment="Center"
        HorizontalAlignment="Center">
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition/>
            <RowDefinition/>
        </Grid.RowDefinitions>
        <Label 
            VerticalAlignment="Center"
            Content="Name:"/>
        <TextBox
            Text="{Binding SelectedPerson.Name,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
            Margin="10"
            Grid.Column="1" 
            Width="100"/>
        <Label 
            VerticalAlignment="Center"
            Grid.Row="1"
            Content="Age:"/>
        <TextBox
            Text="{Binding SelectedPerson.Age,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
            Margin="10"
            Grid.Row="1"
            Grid.Column="1" 
            Width="100"/>


    </Grid>
</Grid>

型号代码示例：

public class PersonModel:INotifyPropertyChanged
{
    public string Name
    {
        get => _name;
        set
        {
            _name = value;
            OnPropertyChanged();
        }
    }

    public int Age
    {
        get => _age;
        set
        {
            _age = value;
            OnPropertyChanged();
        }
    }

    private string _name;
    private int _age;
    //INotifyPropertyChanged implementation
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

和 ViewModel 实现：

 public class ViewModel:INotifyPropertyChanged
{
    public ViewModel()
    {
        Persons = new ObservableCollection<PersonModel>
        {
            new PersonModel
            {
                Name = "Jack",
                Age = 30
            },
            new PersonModel
            {
                Name = "Jon",
                Age = 23
            },
            new PersonModel
            {
                Name = "Max",
                Age = 23
            },
        };
    }

    public ObservableCollection<PersonModel> Persons { get;}

    public PersonModel SelectedPerson
    {
        get => _selectedPerson;
        set
        {
            _selectedPerson = value;
            OnPropertyChanged();
        }
    }

    //INotifyPropertyChanged Implementation
    public event PropertyChangedEventHandler PropertyChanged;
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    private PersonModel _selectedPerson;
}

score 4 · Accepted Answer

我知道我参加这个派对为时已晚，但也许 - 它会对某人有所帮助..

在这里你可以找到我的 ObservableCollectionEx 实现。它有一些特点：

它支持 ObservableCollection 中的所有内容
这是线程安全的
它支持 ItemPropertyChanged 事件（每次触发 Item.PropertyChanged 项目时都会引发）
它支持过滤器（因此，您可以创建 ObservableCollectionEx，将另一个集合作为 Source 传递给它，并使用简单的谓词进行过滤。在 WPF 中非常有用，我在我的应用程序中经常使用此功能）。甚至更多 - 通过 INotifyPropertyChanged 接口过滤跟踪项目的更改。

当然，任何意见表示赞赏;）

score 2 · Accepted Answer

我使用的标准 observablecollection 的简单解决方案：

不要直接添加到您的财产或更改它的内部项目，而是创建一些像这样的临时集合

ObservableCollection<EntityViewModel> tmpList= new ObservableCollection<EntityViewModel>();

并添加项目或对 tmpList 进行更改，

tmpList.Add(new EntityViewModel(){IsRowChecked=false}); //Example
tmpList[0].IsRowChecked= true; //Example
...

然后通过分配将其传递给您的实际财产。

ContentList=tmpList;

这将更改整个属性，从而根据需要通知 INotifyPropertyChanged。

score 2 · Accepted Answer

在 ObservableCollection 列表中触发 OnChange

获取所选项目的索引
从父项中删除项目
在父项中的相同索引处添加项目

例子：

int index = NotificationDetails.IndexOf(notificationDetails);
NotificationDetails.Remove(notificationDetails);
NotificationDetails.Insert(index, notificationDetails);

score 1 · Accepted Answer

这是上述解决方案的扩展方法...

public static TrulyObservableCollection<T> ToTrulyObservableCollection<T>(this List<T> list)
     where T : INotifyPropertyChanged
{
    var newList = new TrulyObservableCollection<T>();

    if (list != null)
    {
        list.ForEach(o => newList.Add(o));
    }

    return newList;
}

score 1 · Accepted Answer

我尝试了这个解决方案，但仅在集合更改时像 RaisePropertyChange("SourceGroupeGridView") 一样对我有用，它会为添加或更改的每个项目触发。

问题出在：

public void EntityViewModelPropertyChanged(object sender, PropertyChangedEventArgs e)
{
     NotifyCollectionChangedEventArgs args = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset);
    OnCollectionChanged(args);
}

NotifyCollectionChangedAction.Reset 这个动作完全重新绑定 groupedgrid 中的所有项目，相当于 RaisePropertyChanged。当您使用它时，所有组的gridview 都会刷新。

如果您只想在 UI 中刷新新项目的组，而不使用重置操作，则需要在 itemproperty 中模拟添加操作，如下所示：

void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{         
    var index = this.IndexOf((T)sender);

    this.RemoveAt(index);
    this.Insert(index, (T)sender);

    var a = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, sender);
    OnCollectionChanged(a);
}

对不起我的英语，感谢基本代码:)，我希望这对某人有所帮助^_^

享受！！

score 1 · Accepted Answer

这是我的实现版本。如果列表中的对象没有实现 INotifyPropertyChanged，它会检查并抛出错误，因此在开发时不能忘记这个问题。在外部，您使用 ListItemChanged 事件确定列表或列表项本身是否已更改。

public class SpecialObservableCollection<T> : ObservableCollection<T>
{
    public SpecialObservableCollection()
    {
        this.CollectionChanged += OnCollectionChanged;
    }

    void OnCollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        AddOrRemoveListToPropertyChanged(e.NewItems,true); 
        AddOrRemoveListToPropertyChanged(e.OldItems,false); 
    }

    private void AddOrRemoveListToPropertyChanged(IList list, Boolean add)
    {
        if (list == null) { return; }
        foreach (object item in list)
        {
            INotifyPropertyChanged o = item as INotifyPropertyChanged;
            if (o != null)
            {
                if (add)  { o.PropertyChanged += ListItemPropertyChanged; }
                if (!add) { o.PropertyChanged -= ListItemPropertyChanged; }
            }
            else
            {
                throw new Exception("INotifyPropertyChanged is required");
            }
        }
    }

    void ListItemPropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        OnListItemChanged(this, e);
    }

    public delegate void ListItemChangedEventHandler(object sender, PropertyChangedEventArgs e);

    public event ListItemChangedEventHandler ListItemChanged;

    private void OnListItemChanged(Object sender, PropertyChangedEventArgs e)
    {
        if (ListItemChanged != null) { this.ListItemChanged(this, e); }
    }


}

score 1 · Accepted Answer

考虑使用 BindingList 并调用 ResetBindings 方法，而不是 ObservableCollection 或 TrulyObservableCollection。

例如：

private BindingList<TfsFile> _tfsFiles;

public BindingList<TfsFile> TfsFiles
{
    get { return _tfsFiles; }
    set
    {
        _tfsFiles = value;
        NotifyPropertyChanged();
    }
}

给定一个事件，例如单击，您的代码将如下所示：

foreach (var file in TfsFiles)
{
    SelectedFile = file;
    file.Name = "Different Text";
    TfsFiles.ResetBindings();
}

我的模型看起来像这样：

namespace Models
{
    public class TfsFile 
    {
        public string ImagePath { get; set; }

        public string FullPath { get; set; }

        public string Name { get; set; }

        public string Text { get; set; }

    }
}

score 1 · Accepted Answer

我在这里看到大多数示例将 INotifyPropertyChanged 约束置于强制模型实现 INotifyPropertyChanged 的泛型类型上。

如果您遵循在模型上放置 INotifyPropertyChanged 约束的示例，则与在模型中实现 INotifyPropertyChanged 并允许 ObservableCollection 处理更新属性更改一样好。

但是如果你不希望你的模型实现 INotifyPropertyChanged，你可以试试这个。

CustomObservableCollection

 public class CustomObservableCollection<T> : ObservableCollection<T>
 {

      public void Refresh(T item)
      {
          var index = IndexOf(item);

          RemoveAt(index);
          Insert(index, item);

          OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item, IndexOf(item)));
      }
 }

模型

public class Person
{
    public string FirstName { get; set; }   
    public string LastName { get; set; }   
    public int Age { get; set; }   
}

视图模型

 public class PersonViewModel
 {       

     public PersonViewModel(){

          People=new CustomObservableCollection<Person>();

     }
    
     private void AddPerson(){

        People.Add(new Person(){
            FirstName="John",
            LastName="Doe",
            Age=20
        });

      }
    
      private void UpdatePerson(){

         var person=People.Where(...).FirstOrDefault();
         person.Age=25;

         People.Refresh(person);
      }

      public CustomObservableCollection<Person> People { get; set; } 
    
    }

score 0 · Accepted Answer

您还可以使用此扩展方法轻松地为相关集合中的项目属性更改注册处理程序。此方法会自动添加到所有实现 INotifyCollectionChanged 的集合中，这些集合包含实现 INotifyPropertyChanged 的项目：

public static class ObservableCollectionEx
{
    public static void SetOnCollectionItemPropertyChanged<T>(this T _this, PropertyChangedEventHandler handler)
        where T : INotifyCollectionChanged, ICollection<INotifyPropertyChanged> 
    {
        _this.CollectionChanged += (sender,e)=> {
            if (e.NewItems != null)
            {
                foreach (Object item in e.NewItems)
                {
                    ((INotifyPropertyChanged)item).PropertyChanged += handler;
                }
            }
            if (e.OldItems != null)
            {
                foreach (Object item in e.OldItems)
                {
                    ((INotifyPropertyChanged)item).PropertyChanged -= handler;
                }
            }
        };
    }
}

如何使用：

public class Test
{
    public static void MyExtensionTest()
    {
        ObservableCollection<INotifyPropertyChanged> c = new ObservableCollection<INotifyPropertyChanged>();
        c.SetOnCollectionItemPropertyChanged((item, e) =>
        {
             //whatever you want to do on item change
        });
    }
}

score 0 · Accepted Answer

对我来说有助于这个技巧 - removeAt 并插入替换项目，在这个“更改”期间 - 事件正确上升。

private ObservableCollection<CollectionItem> collection = new ObservableCollection<CollectionItem>();

public void Update(CollectionItem newItem, CollectionItem old ) {
            int j = collection.IndexOf(old);
            collection.RemoveAt(j); 
            collection.Insert(j, newComplexCondition);
        }

score -1 · Accepted Answer

2行代码的简单解决方案。只需使用复制构造函数。无需编写 TrulyObservableCollection 等。

例子：

        speakers.list[0].Status = "offline";
        speakers.list[0] = new Speaker(speakers.list[0]);

另一种没有复制构造函数的方法。您可以使用序列化。

        speakers.list[0].Status = "offline";
        //speakers.list[0] = new Speaker(speakers.list[0]);
        var tmp  = JsonConvert.SerializeObject(speakers.list[0]);
        var tmp2 = JsonConvert.DeserializeObject<Speaker>(tmp);
        speakers.list[0] = tmp2;

c# - ObservableCollection 没有注意到其中的项目何时更改（即使使用 INotifyPropertyChanged）

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