如何在 ListView 中查找特定的 ListViewItem - C# (WPF)

Question

我创建了包含三列的 ListView (C#-WPF)：数字、操作和文件。首先，我向 ListView 添加了几个不同的项目，“数字”随着添加的每个条目而增加，“操作”正在记录到底发生了什么（移动/重命名/删除），“文件”列显示其中文件发生了一个动作。

XAML：

<ListView x:Name="ActionFile" HorizontalAlignment="center" Height="100" VerticalAlignment="bottom" Width="780" Margin="20,0,0,0">
    <ListView.View>
        <GridView>
            <GridViewColumn Header="Number" Width="40" DisplayMemberBinding="{Binding NumberX}"/>
            <GridViewColumn Header="Action" Width="200" DisplayMemberBinding="{Binding ActionX}"/>
            <GridViewColumn Header="File" Width="350" DisplayMemberBinding="{Binding FileX}"/>
        </GridView>
    </ListView.View>
</ListView>

C#：

public class FileActionEntry
{
    public int NumberX { get; set; }
    public string ActionX { get; set; }
    public string FileX { get; set; }
}

ActionFile.Items.Add(new FileActionEntry() { NumberX = numValue, ActionX = actionValue, FileX = fileValue });

现在，我正在尝试创建一个 foreach 循环，该循环将检查是否对特定文件执行了特定操作，然后从 ListView 中清除该条目并返回其“数字”值。我有几种不同的方法，但我不知道如何从项目中提取列值。我认为可以通过使用 '.SubItems' 来完成，但它似乎不适用于 WPF。

Answer 1

这样做的最佳方法是考虑将您的 listView ItemSource 绑定到 ObservableCollection，实现 INotifyPropertyChanged 接口，对该集合的任何更新都将自动反映在 UI 上。

考虑以下基于您的示例，其中在 TextBox 中提供文件名的条目从集合中删除：

Xaml

<Grid>
    <Grid VerticalAlignment="Top">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <Button Content="Process" Click="ButtonBase_OnClick"/>
        <TextBox Grid.Column="1" Margin="2" Text="{Binding SearchText, Mode=TwoWay}"/>
    </Grid>
    <ListView x:Name="ActionFile" HorizontalAlignment="center" Height="100" VerticalAlignment="bottom" Width="780" Margin="20,0,0,0" ItemsSource="{Binding FileActionEntryCollection}">
        <ListView.View>
            <GridView>
                <GridViewColumn Header="Number" Width="40" DisplayMemberBinding="{Binding NumberX}"/>
                <GridViewColumn Header="Action" Width="200" DisplayMemberBinding="{Binding ActionX}"/>
                <GridViewColumn Header="File" Width="350" DisplayMemberBinding="{Binding FileX}"/>
            </GridView>
        </ListView.View>
    </ListView>
</Grid>

背后的代码

 public class FileActionEntry
{
    public int NumberX { get; set; }
    public string ActionX { get; set; }
    public string FileX { get; set; }
}
public partial class MainWindow : Window, INotifyPropertyChanged
{
    private string _searchText = "";
    public string SearchText
    {
        get
        {
            return _searchText;
        }
        set
        {
            if (_searchText == value)
            {
                return;
            }

            _searchText = value;
            OnPropertyChanged();
        }
    }
    private ObservableCollection<FileActionEntry> _fileActionEntryCollection = new ObservableCollection<FileActionEntry>()
    {
        new FileActionEntry(){ ActionX = "Moved", FileX = "File1", NumberX = 1},
        new FileActionEntry(){ ActionX = "Renamed", FileX = "File2", NumberX = 2},
        new FileActionEntry(){ ActionX = "Removed", FileX = "File3", NumberX = 3}
    };


    public ObservableCollection<FileActionEntry> FileActionEntryCollection
    {
        get
        {
            return _fileActionEntryCollection;
        }

        set
        {
            if (_fileActionEntryCollection == value)
            {
                return;
            }

            _fileActionEntryCollection = value;
            OnPropertyChanged();
        }
    }

    public MainWindow()
    {
        InitializeComponent();

    }

    public event PropertyChangedEventHandler PropertyChanged;

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
    {
        if (FileActionEntryCollection.Any(f => f.FileX == SearchText))
            FileActionEntryCollection.Remove(FileActionEntryCollection.First(f => f.FileX == SearchText));
    }
}

Answer 2

您应该（必须）使用数据绑定 (Data Binding Overview in WPF)。这会让你的生活轻松很多。数据绑定上下文中的一个基本类是ObservableColllection。此集合将通知绑定目标任何更改（例如，添加或删除）。所有ItemsControl 喜欢ListView 的人都会听取这些变化，并将更新他们的视图以反映这些变化。所以你永远不需要直接访问控件来添加或删除项目。

视图模型是绑定源：

class ViewModel : INotifyPropertyChanged
{
  // Ctor
  public ViewModel() => this.FileActionEntries = new ObservableCollection<FileActionEntry>();

  private void AddFileActionToListView()
  {
    var newFileEntry = new FileActionEntry() { NumberX = numValue, ActionX = actionValue, FileX = fileValue };

    // Add an item to the ListView
    // or any other control that binds to FileActionEntries (ObservableCollection)
    this.FileActionEntries.Add(newFileEntry);
  }

  private int CheckFileAction(string action, string file)
  {
    // Throws an exception if file not found
    FileActionEntry fileEntry = this.FileActionEntries.First(entry => entry.FileX.Equals(file, StringComparison.OrdinalIgnoreCase));

    // TODO: Check action

    // Remove an item from the ListView
    // or any other control that binds to FileActionEntries (ObservableCollection)
    this.FileActionEntries.Remove(fileEntry);

    return fileEntry.NumberX;
  }

  private ObservableCollection<FileActionEntry> fileActionEntries;
  public ObservableCollection<FileActionEntry> FileActionEntries
  {
    get => this.fileActionEntries;
    set 
    { 
      this.fileActionEntries = value; 
      OnPropertyChanged();
    }
  }

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

XAML 绑定 ItemsSource:

<Window>
  <Window.DataContext>
    <ViewModel />
  </Window.DataContext>

  <ListView x:Name="ActionFile" 
            ItemsSource="{Binding FileActionEntries}" >
    <ListView.View>
      <GridView>
          <GridViewColumn Header="Number" Width="40" DisplayMemberBinding="{Binding NumberX}"/>
          <GridViewColumn Header="Action" Width="200" DisplayMemberBinding="{Binding ActionX}"/>
          <GridViewColumn Header="File" Width="350" DisplayMemberBinding="{Binding FileX}"/>
      </GridView>
    </ListView.View>
  </ListView>
</Window>