Question

我有一个带有DataGrid和ComboBox的WPF MVVM应用程序，这些应用程序绑定到ViewModel类中的相同实体列表。我想通过ComboBox选择过滤DataGrid条目，这样做的正确方法是什么？由于我正在使用MVVM，我希望通过数据绑定实现这一点，并避免使用无用的代码。

我的XAML代码如下所示

<DataGrid ItemsSource="{Binding Posts}" AutoGenerateColumns="False" IsReadOnly="True">
   <DataGrid.Columns>
      <DataGridTextColumn Header="Id" Binding="{Binding Id}" />
      <DataGridTextColumn Header="Title" Binding="{Binding Title}" />
      <DataGridTextColumn Header="BlogUrl" Binding="{Binding Blog.Url}" />
   </DataGrid.Columns>
</DataGrid>

<ComboBox ItemsSource="{Binding Posts}"
          DisplayMemberPath="Blog.Url" />

视图模型

public class MainWindowViewModel
{
    private SqliteDbContext context;
    public List<Post> Posts { get; set; }

    public MainWindowViewModel()
    {
        context = new SqliteDbContext();
        Posts = context.Posts.Include(p => p.Blog).ToList();
    }
}

此外，使用此代码，我的ComboBox显示了Urls的重复项，如何区分这些值？

感谢。

Answer 1

您可以将ComboBox绑定到您在视图模型中创建的唯一网址的集合。

然后，您可以通过将DataGrid的{{1}}属性绑定到过滤SelectedItem源集合的视图模型的源属性来过滤ComboBox。

请参阅以下代码示例。

查看型号：

Posts

查看：

public class MainWindowViewModel : INotifyPropertyChanged { private readonly SqliteDbContext context; private readonly List<Post> _allPosts; public MainWindowViewModel() { context = new SqliteDbContext(); _allPosts = context.Posts.Include(p => p.Blog).ToList(); _posts = _allPosts; Urls = _allPosts.Where(p => p.Blog != null && !string.IsNullOrEmpty(p.Blog.Url)).Select(p => p.Blog.Url).ToList(); } private List<Post> _posts; public List<Post> Posts { get { return _posts; } set { _posts = value; NotifyPropertyChanged(); } } public List<string> Urls { get; set; } private string _url; public string Url { get { return _url; } set { _url = value; NotifyPropertyChanged(); Posts = _allPosts.Where(p => p.Blog != null && p.Blog.Url == _url).ToList(); } } public event PropertyChangedEventHandler PropertyChanged; private void NotifyPropertyChanged([CallerMemberName] string propertyName = "") { if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } }

Answer 2

这应该可以解决问题。

<强>视图模型：

public class MainWindowViewModel
{
    private SqliteDbContext context;

    public ObservableCollection<Post> Posts { get; set; }
    private string _selectedUrl;
    public ICollectionView PostsView { get; set; }
    public MainWindowViewModel()
    {
        context = new SqliteDbContext();
        Posts = new ObservableCollection<Post>(context.Posts.Include(p => p.Blog));
        PostsView = new CollectionViewSource { Source = Posts }.View;
        PostsView.Filter = post => SelectedUrl == null || SelectedUrl == ((Post)post).Blog.Url;
    }

    public string SelectedUrl
    {
        get
        {
            return _selectedUrl;
        }
        set
        {
            _selectedUrl = value;
            PostsView.Refresh();
        }
    }
}

<强> XAML ：

<DataGrid ItemsSource="{Binding PostsView}" AutoGenerateColumns="False" IsReadOnly="True">
    <DataGrid.Columns>
        <DataGridTextColumn Header="Id" Binding="{Binding Id}" />
        <DataGridTextColumn Header="Title" Binding="{Binding Title}" />
        <DataGridTextColumn Header="BlogUrl" Binding="{Binding Blog.Url}" />
    </DataGrid.Columns>
</DataGrid>

<ComboBox ItemsSource="{Binding Posts}"
          DisplayMemberPath="Blog.Url" 
          SelectedValuePath="Blog.Url"
          SelectedValue="{Binding SelectedUrl}"/>

使用ComboBox进行WPF MVVM DataGrid过滤

2 个答案: