CollectionViewSource，如何筛选数据？ [英] CollectionViewSource, how to filter data?
问题描述
我绑定一个ComboBox实体，但我想要的数据进行过滤。
I am binding a ComboBox to Entities but I want the data filtered.
到现在为止我已经尝试了两种方式：
Up to now I have tried two ways:
- 简单之一：直接涂于过滤器的对象集throught
LINQ到实体 - 设置过滤事件处理程序的描述上
MSDN
- "simple" one: Apply the filter directly to the ObjectSet throught LINQ to Entities
- setting a filtering event handler as described on msdn
我是通过第一种方式不满意，首先是因为生成的数据库查询包含WHERE子句，所以不是所有的整个数据必须从远程数据库检索....
I am satisfied by the first approach, above all because the query generated to the database contains a WHERE clause, so not all the whole data have to be retrieved from the remote db....
然而，＃2的方法是通过更为灵活，如果在运行时我想改变应用的过滤......我按照MSDN上的例子，但我得到一个异常，为什么？
However, the #2 approach is by far more flexible, if at runtime i'd like to change the filtering applied... I have followed the example on msdn, but I get an exception, why?
所以，我的问题是：结果
1.哪种方法比较好结果
2.为什么我得到的例外呢？
So, my questions are:
1. Which approach is better
2. Why I get the exception?
下面是我的code：
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;
}
}
}
修改：我曾尝试推行视图上的过滤器属性，而不是设置事件处理程序：
EDIT: I have tried implementing the Filter property on the View rather than setting the 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);
}
而现在我得到的不那么有用的异常：
System.NotSupportedException：不支持指定的方法。
在System.Windows.Data.CollectionView.set_Filter（predicate`1值）
System.NotSupportedException: Specified method is not supported. at System.Windows.Data.CollectionView.set_Filter(Predicate`1 value)
修改
XAML code：
XAML code:
<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，我想这个问题是在XAML绑定，而不是在背后code ...
推荐答案
铝最后我找到了一个解决方案，因为还发布<一个href=\"http://stackoverflow.com/questions/2702434/entity-framework-4-0-databinding-with-sorting-not-working/2720540#2720540\">in这个问题
到expliticy申报集合类型：
Al last I have found a solution, as posted also in this question to expliticy declare the type of the Collection:
CollectionViewType =的ListCollectionView
因此，在XAML添加的集合类型：
So in XAML added the Collection type:
<CollectionViewSource x:Key="tSCHEDEViewSource" d:DesignSource="{d:DesignInstance my:TSCHEDE, CreateList=True}" CollectionViewType="ListCollectionView">
</CollectionViewSource>
和在code现在事件处理程序如下：
And in code now the Event Handler works:
myCollectionViewSource.Filter += new FilterEventHandler(filterSource);
唯一遗憾的是，我不明白为什么，什么东西显然是如此简单，我有手在XAML，迫使它???
对我来说这似乎是一个黑客，也很容易出错...
The only regret is that I did not understand why, for something apparently so simple, I have to force it "by hand" in XAML ??? To me this seems like an hack, and also very error prone...
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