INotifyPropertyChanged 不工作 MVVM

Question

我有一个 Observable 集合，但是在更新集合之后，即使在引发 Property Changed 事件后，我的 Listview 也没有更新，请参见下面的代码：-

看下面的 XAML：-

 <ListView  Grid.Row="1" Grid.Column="0" Name="lvGroups" Margin="0,34,0,0" 
Grid.RowSpan="2" ItemsSource="{Binding Path=*VideoGroupList*,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
<GridView>
<GridViewColumn Width="150" DisplayMemberBinding="{Binding *Name*}" />
</GridView>

看下面的类

 public class VideoGroupViewModel : ObservableEnitiy
 {
   public ObservableCollection<Group> VideoGroupList { get; set; }
 }

  public abstract class ObservableEnitiy : INotifyPropertyChanged
 {
   public event PropertyChangedEventHandler PropertyChanged;
   protected virtual void OnPropertyChanged(string propertyName)
   {
     this.VerifyPropertyName(propertyName);
      if (this.PropertyChanged != null)
        {
            var e = new PropertyChangedEventArgs(propertyName);
            this.PropertyChanged(this, e);
        }
   }
 }

[Serializable]
public class Group : PropertyChangedNotification
{
    public int ID { get; set; }
    [Required(ErrorMessage = "Group name is required.")]
    public string *Name*
    {
        get { return GetValue(() => Name); ; }
        set
        {
            SetValue(() => Name, value);
        }
    }
    [XmlIgnore]
    public bool IsSelected { get; set; }
}  


     protected T GetValue<T>(Expression<Func<T>> propertySelector)
    {
        string propertyName = GetPropertyName(propertySelector);

        return GetValue<T>(propertyName);
    }

我这样叫

 VideoGroupList = new ObservableCollection<Group>(videoGroupManager.GetVideoGroups());
 OnPropertyChanged("VideoGroupList");

Answer 1

添加以下 using 语句：

using System.Collections.Generic;
using System.Linq;

将您的 VideoGroupList 行更改为：

    VideoGroupList.Clear();
    videoGroupManager.GetViewGroups().ToList().ForEach(x => VideoGroupList.Add(x));

这更好地利用了 ObservableCollection 中内置的更改通知

Answer 2

根据 MSDN 文档，CollectionChanged 将在添加、删除和更改 ObservableCollection 中的元素时引发。然而，我发现情况并非如此。 ObservableCollection.CollectionChanged 只会在添加/删除时抛出。 我改用this FullyObservableCollection here，修改后让 T 成为我的 ViewModelBase 类，而不是直接使用 INotifyPropertyChanged。

当我声明我的属性时，我使用带有以下输出的 sn-p： private FullyObservableCollection<Group> _videoGroupList; public FullyObservableCollection<Group> VideoGroupList { get { return _videoGroupList; } set { if(_videoGroupList == value) return; var nil = _videoGroupList == null; _videoGroupList = value; // If null before and not after (declaring it after being null), // call OnPropertyChanged on Change of Collection. if(nil && _videoGroupList != null) _videoGroupList.CollectionChanged += (s,e) => OnPropertyChanged(nameof(VideoGroupList)); OnPropertyChanged(); } } 这样，您将始终对集合及其每个成员的添加、删除、替换和更改操作有 INotifyPropertyChanged 通知。这将为您节省很多麻烦，因为如果其中数十万个属性之一发生更改，您无需重新实例化整个集合。 不过请记住在构造函数中对其进行初始化。 :)