c# - 如何检查模型列表中的重复条目？

Question

我有一个带有 ListView 的 MVVM 应用程序由 EditableTextblock 组成在 DataTemplate 中(like this)。

这是我的模型:

public class MyModel
{
    private string _data;
    public string Data
    {
        get { return _data; }
        set { _data = value; }
    }
}

我的 View 模型暴露了 ObservableCollection的 MyModel :

public class MyViewModel
{
    [...]
    public ObservableCollection<Mymodel> models = new ObservableCollection<MyModel>();
}

并在绑定(bind)到 ListView 的 View 中:

<ListView ItemsSource={Binding models}>
    <!-- code removed for more visibility -->
    <DataTemplate>
         <controls:EditableTextblock Text="{Binding Data, Mode=TwoWay}" />
    </DataTemplate>
    <!-- ... -->
</ListView>

您是否有任何线索表明，当我在列表中的某个项目中更新数据成员的值时，会检查集合中是否已存在值？

例如，如果我将一个字段更新为“值 1”，它会检查模型集合中是否有一个成员 Data 已经具有该值。

如果它找到一个，它会在成员数据的末尾添加一个“0”。

Answer 1

前提是 MyModel类实现 INotifyPropertyChanged并提出 PropertyChanged Data 时的事件属性已设置，您可以在 View 模型中处理此问题:

public class MyViewModel
{
    public ObservableCollection<MyModel> models = new ObservableCollection<MyModel>();

    public MyViewModel()
    {
        models.CollectionChanged += Models_CollectionChanged;
    }

    private void Models_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        if (e.NewItems != null)
        {
            foreach (object model in e.NewItems)
            {
                (model as INotifyPropertyChanged).PropertyChanged
                    += new PropertyChangedEventHandler(Model_PropertyChanged);
            }
        }

        if (e.OldItems != null)
        {
            foreach (object model in e.OldItems)
            {
                (model as INotifyPropertyChanged).PropertyChanged
                    -= new PropertyChangedEventHandler(Model_PropertyChanged);
            }
        }
    }

    private void Model_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        MyModel updatedModel = sender as MyModel;
        MyModel duplicate = models.FirstOrDefault(x => x != updatedModel && x.Data == updatedModel.Data);
        if(duplicate != null)
        {
            updatedModel.Data += "0";
        }
    }
}

public class MyModel : INotifyPropertyChanged
{
    private string _data;
    public string Data
    {
        get { return _data; }
        set { _data = value; NotifyPropertyChanged(); }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}