Question

WPF和MVVM的新手。我尝试将带有 FilterEventHandler 的过滤器用于 CollectionViewSource 。我试图在属性更改中添加过滤器（ p_sSelectedCreatedDate ）。问题是当我将过滤器添加到 CollectionViewSource 对象时， FilterEventHandler 委托函数（ FilterByCreatedDate ）未触发。当我调试时，我可以在代码中看到正在添加过滤器，如下面一行所示。

CVS.Filter += new FilterEventHandler(FilterByCreatedDate);

但是，代码返回时不执行 FilterByCreatedDate 。请注意，我只发布此问题所必需的代码部分以及继承自 INotifyPropertyChanged 的 BaseViewModel 。

以下是必要的代码。

ScanBatchWindow.xaml

<Window x:Class="BatchManPOC.ScanBatchWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:BatchManPOC"
    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
    xmlns:cmdBehavior="clr-namespace:BatchManPOC.CmdBehavior"
    xmlns:video="clr-namespace:BatchManPOC.Video"
    xmlns:Custom="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    mc:Ignorable="d"
    Title="ScanBatchWindow" 
    Height="800"
    Width="800">
<Window.Resources>
    <CollectionViewSource Source="{Binding p_ListBatches}" x:Key="CVS"/>
</Window.Resources>
     <Grid>
         <Grid.RowDefinitions>
               <RowDefinition/>
         </Grid.RowDefinitions>
              <Custom:DataGrid ItemsSource="{Binding Source={StaticResource CVS}}" Margin="8" Grid.Row="0" AutoGenerateColumns="True"  IsReadOnly="True">
</Custom:DataGrid>
        </Grid>
</Window>

ScanBatchViewModel.cs

public class ScanBatchViewModel : BaseViewModel
{
    public ObservableCollection<Batch> p_ListBatches { get; set; }
    public CollectionViewSource CVS { get; set; }

    private string _p_sSelectedCreatedDate;
    public string p_sSelectedCreatedDate {
        get
        {
            return _p_sSelectedCreatedDate;
        }
        set
        {
            _p_sSelectedCreatedDate = value;
            ApplyFilter(!string.IsNullOrEmpty(_p_sSelectedCreatedDate) ? FilterField.CREATED_DATE : FilterField.NONE);
        }
    }

    public ScanBatchViewModel()
    {
        p_ListBatches = new ObservableCollection<Batch>();

        LoadBatches();
        CVS = new CollectionViewSource();
    }

    private void ApplyFilter(FilterField field)
    {
        switch (field)
        {
            case FilterField.CREATED_DATE:
                AddCreatedDateFilter();
                break;
            default:
                break;
        }
    }

    public void AddCreatedDateFilter()
    {
        // see Notes on Adding Filters:
        if (p_bCanRemoveCreatedDateFilter)
        {
            CVS.Filter -= new FilterEventHandler(FilterByCreatedDate);
            CVS.Filter += new FilterEventHandler(FilterByCreatedDate);
        }
        else
        {
            CVS.Filter += new FilterEventHandler(FilterByCreatedDate);
            p_bCanRemoveCreatedDateFilter = true;
        }
    }

    private void FilterByCreatedDate(object sender, FilterEventArgs e)
    {
        // see Notes on Filter Methods:
        var src = e.Item as Batch;
        if (src == null)
            e.Accepted = false;
        else if (string.Compare(p_sSelectedCreatedDate, src.Date) != 0)
            e.Accepted = false;   
    }
}

Answer 1

CollectionViewSource.Filter是一个事件。当CollectionViewSource需要过滤内容时，它将被触发。当CollectionViewSource更新视图时会发生这种情况。

要更新视图，请调用相应的方法：

CVS.View.Refresh();

请注意，您的方法AddCreatedDateFilter()可以为Filter事件添加多个事件处理程序。将为集合中的每个项调用每个事件处理程序。这可能会导致性能问题。并且所有事件处理程序都是相同的，所以这也没用。

因此，请确保您只为此事件添加一个事件处理程序。

FilterEventHandler委托函数未触发

1 个答案: