如何从CollectionViewSource获取项目数？

Question

I am using CollectionViewSource to filter the records displayed in a ListBox. The xaml follows.

   <Window x:Class="WPFStarter.ListBoxItemsFilter.ListBoxFilterUsingCollectionViewSource"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        x:Name="userControl"
        Title="ListBoxFilterUsingCollectionViewSource" Height="300" Width="300">
        <Window.Resources>
        <CollectionViewSource Source="{Binding ElementName=userControl, Path=DataContext.Items}"
                              x:Key="cvs" Filter="CollectionViewSource_Filter"/>
        </Window.Resources>
    <StackPanel Orientation="Vertical">
        <TextBox x:Name="txtSearch" TextChanged="txtSearch_TextChanged"/>
        <TextBlock x:Name="txtSummary" Grid.Column="0" HorizontalAlignment="Right" VerticalAlignment="Bottom"  FontSize="8"></TextBlock>
        <ListBox ItemsSource="{Binding Source={StaticResource cvs}}" DisplayMemberPath="First"/>
    </StackPanel>

</Window>

And here is my code-behing ( please don;t mind this code-behind, in the real application i am using the best of MVVM for this scenario).

 public partial class ListBoxFilterUsingCollectionViewSource : Window
    {
        private string _text="";
        private readonly CollectionViewSource _viewSource;

        public ListBoxFilterUsingCollectionViewSource()
        {
            InitializeComponent();
            _viewSource = this.FindResource("cvs") as CollectionViewSource;
        }

        private void CollectionViewSource_Filter(object sender, FilterEventArgs e)
        {
            var character = e.Item as Character;
            e.Accepted = character != null && character.First.ToLower().Contains(_text.ToLower());
        }

        private void txtSearch_TextChanged(object sender, TextChangedEventArgs e)
        {
            _text = txtSearch.Text;
            _viewSource.View.Refresh();

            SetSummary();
        }

        private void SetSummary()
        {                
            var initialCount = 10; //HELP????
            var filteredCount = 10; //HELP????
            txtSummary.Text = String.Format("{0} of {1}", filteredCount, initialCount);
        }
    }

QUESTION: I Need help in writing the "SetSummary" method, wherein i can get the "initialCount" and the "filteredCount" from CollectionViewSource object.

Thanks for your interest.

Answer 1

你也可以做_viewSource.View.Cast<object>().Count()用于过滤列表和_viewSource.View.SourceCollection.Cast<object>().Count()的原件。

Answer 2

I think the better solution is, as usual, Linq!

_viewSource.View.Cast<[your_type]>().Count();

...or...

_viewSource.View.Cast<object>().Count();

...if you don't know the items' type at runtime!

Answer 3

The source collection and collectionview both implements IEnumerable so you can always iterate over them and count how many are in them. But I would only recommend doing this if you have no access to the actual collection you used as source.

private void SetSummary() 
{
    int initialCount = 0;
    foreach(var item in _viewSource.View.SourceCollection)
    {
        initialCount++;
    }

    int filteredCount = 0;
    foreach (var item in _viewSource.View)
    {
        filteredCount++;
    }
}

Answer 4

If you're doing MVVM, you could have your VM create a collection view rather than one being created on your behalf by the CollectionViewSource . Then, you have control over what type of CVS is created, so you can create a ListCollectionViewSource , which has a Count property. It really depends on the properties of the data you're filtering.

Answer 5

var count = DataGrid.ItemsSource.OfType<object>().Count();

Answer 6

public static int Count(this ICollectionView view)
    {
        var index = 0;
        foreach (var unused in view)
        {
            index++;
        }
        return index;
    }