CollectionViewSource,如何过​​滤数据?

时间:2013-01-24 09:08:19

标签: c# binding filtering collectionviewsource

我将ComboBox绑定到实体,但我想要过滤数据。

到目前为止,我尝试了两种方法:

  • “simple”one:将过滤器直接应用于ObjectSet LINQ to Entities
  • 如上所述设置过滤事件处理程序 msdn

我对第一种方法感到满意,首先是因为生成到数据库的查询包含WHERE子句,所以不是所有的数据都必须从远程数据库中检索....

然而,#2方法更灵活,如果在运行时我想更改应用的过滤...我已经按照msdn上的示例,但我得到一个例外,为什么?

所以,我的问题是:
1.哪种方法更好 2.为什么我得到例外?

这是我的代码:

 private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
        //Do not load your data at design time.
        if (!System.ComponentModel.DesignerProperties.GetIsInDesignMode(this))
        {
            //Load your data here and assign the result to the CollectionViewSource.
            System.Windows.Data.CollectionViewSource myCollectionViewSource =
                (System.Windows.Data.CollectionViewSource)
                this.Resources["tSCHEDEViewSource"];

            // If I use this I get the data filtered on startup, but is it the right mode?
            //myCollectionViewSource.Source = _context.TSCHEDE.Where(s => s.KLINEA == kLinea && s.FCANC == "T").OrderBy(s => s.DSCHEDA).OrderByDescending(s => s.DSTORICO);

            // Instead If I apply my custom filtering logic
            myCollectionViewSource.Filter += new FilterEventHandler(filterSource);

            myCollectionViewSource.Source = _context.TSCHEDE; // ... Here i get an exception: 
            // 'System.Windows.Data.BindingListCollectionView' view does not support filtering. ???
        }
    }


    private void filterSource(object sender, FilterEventArgs e)
    {
        TSCHEDE scheda = e.Item as TSCHEDE;
        if (scheda != null)
        {
            if (scheda.KLINEA == 990)
            {
                e.Accepted = true;
            }
            else
            {
                e.Accepted = false;
            }
        }
    }

编辑:我尝试在View上实现Filter属性,而不是设置EventHandler:

myCollectionView = (BindingListCollectionView)myCollectionViewSource.View;
myCollectionView.Filter = new Predicate<object>(Contains);

public bool Contains(object de)
    {
        TSCHEDE scheda = de as TSCHEDE;
        return (scheda.KLINEA == 990);
    }

现在我得到了不那么有用的例外:

  

System.NotSupportedException:不支持指定的方法。      在System.Windows.Data.CollectionView.set_Filter(Predicate`1 value)

修改

XAML代码:

<UserControl.Resources>
    <CollectionViewSource x:Key="tSCHEDEViewSource" d:DesignSource="{d:DesignInstance my:TSCHEDE, CreateList=True}"  >
    </CollectionViewSource>
    <DataTemplate x:Key="SchedaTemplate">
        <StackPanel Orientation="Horizontal" >
            <TextBlock Text="{Binding Path=KSCHEDA}" Width="60"></TextBlock>
            <TextBlock Text="{Binding Path=DArticolo}" Width="200"></TextBlock>
            <TextBlock Text=" - " Width="40"></TextBlock>
            <TextBlock Text="{Binding Path=DSTORICO}" Width="150"></TextBlock>
        </StackPanel>
    </DataTemplate>
</UserControl.Resources>
<Grid Background="PapayaWhip" DataContext="{StaticResource tSCHEDEViewSource}" DataContextChanged="StartHere" Name="rootGrid">
    <ComboBox ItemTemplate="{StaticResource SchedaTemplate}" Grid.Column="1" Grid.Row="1" Height="23" HorizontalAlignment="Left" ItemsSource="{Binding}" Margin="23,129,0,0" Name="tSCHEDEComboBox1" SelectedValuePath="KSCHEDA" VerticalAlignment="Top" Width="393">
        <ComboBox.ItemsPanel>
            <ItemsPanelTemplate>
                <VirtualizingStackPanel />
            </ItemsPanelTemplate>
        </ComboBox.ItemsPanel>
    </ComboBox>
</Grid>

现在我认为问题出在XAML Binding中,而不是代码背后......

3 个答案:

答案 0 :(得分:8)

检查

1)CollectionView Filtering

过滤需要基于过滤器发生的委托(谓词)。谓词根据它返回的值true或false接收项目,它选择或取消选择元素。

this.Source.Filter = item => {
    ViewItem vitem = item as ViewItem;
    return vItem != null && vitem.Name.Contains("A");
};

2) FIltering the data Dynamically

答案 1 :(得分:7)

最后我找到了一个解决方案,也发布了in this question 明确声明Collection的类型:

<强> CollectionViewType = “的ListCollectionView”

所以在XAML中添加了Collection类型:

<CollectionViewSource x:Key="tSCHEDEViewSource" d:DesignSource="{d:DesignInstance my:TSCHEDE,  CreateList=True}" CollectionViewType="ListCollectionView">
    </CollectionViewSource>

现在代码中的事件处理程序可以运行:

myCollectionViewSource.Filter += new FilterEventHandler(filterSource);

唯一的遗憾是我不明白为什么,因为显然这么简单,我必须在XAML中“手动”强制它??? 对我而言,这似乎是一种黑客攻击,也非常容易出错......

答案 2 :(得分:0)

<TextBox x:Name="FilterTextBox">
    <b:Interaction.Triggers>
        <b:EventTrigger EventName="TextChanged">
            <b:CallMethodAction
                MethodName="Refresh"
                TargetObject="{Binding View, BindsDirectlyToSource=True, Source={StaticResource tSCHEDEViewSource}}" />
        </b:EventTrigger>
    </b:Interaction.Triggers>
</TextBox>