xaml 中的 ComboBox 数据过滤 [英] ComboBox data filtering in xaml

问题描述

我正在使用 Telerik 组合框，但我认为该问题与标准 wpf 组合框有关.该控件绑定到TableRecord"的可观察集合，该对象如下所示:

I am using a Telerik combobox but I think the question is relevant to the standard wpf combobox. The control is bound to an observable collection of "TableRecord" where this object looks like this:

public enum RecordState
{
    Orginal, Added, Modified, Deleted
}

public class TableRecord<T> 
{
    public Guid Id { get; set; }
    public string DisplayName { get; set; }
    public T Record { get; set; }
    public RecordState State { get; set; }

    public TableRecord(Guid id, string displayName, T record, RecordState state)
    {
        Id = id;
        DisplayName = displayName;
        Record = record;
        State = state;
    }
}

这些TableRecords"是这样保存和公开的:

These "TableRecords" are held and exposed like this:

private ObservableCollection<TableRecord<T>> _recordCollection = new ObservableCollection<TableRecord<T>>();
public ObservableCollection<TableRecord<T>>  Commands 
{
    get
    {
           return _recordCollection;
    }
}

我的 xaml 如下所示:

My xaml looks like this:

<telerik:RadComboBox ItemsSource="{Binding Commands}" DisplayMemberPath="DisplayName" SelectedValuePath="Id" Height="22" SelectedItem="{Binding SelectedCommand, Mode=TwoWay}" />

我想要做的是更改 xaml(如果可能)，以便它显示集合中除State"值设置为Deleted"的项目之外的所有项目.

What I want to do is change the xaml (if possible) so that it shows all the items in the collection apart from the items that have the "State" value set to "Deleted".

我有一个想法，我可以使用数据触发器来做到这一点，因为我过去曾使用它们根据内容设置文本颜色，但不确定是否可以按我需要的方式进行过滤.

I’ve got an idea that I may be able to do this using data triggers as I’ve used them in the past to set text colour based on content but am not sure if I can filter in the way I need.

推荐答案

最好的方法是使用 CollectionViewSource 进行过滤.在资源中定义一个集合视图源并键入它.

Best approach is to use CollectionViewSource for filtering. Define a collection view source in resources and key it.

<Window.Resources>
    <CollectionViewSource Source="{Binding Commands}" x:Key="source"/>
</Window.Resources>
<Grid>
    <ComboBox VerticalAlignment="Center" HorizontalAlignment="Center" Width="200" 
              ItemsSource="{Binding Source={StaticResource source}}"
              DisplayMemberPath="DisplayName"/>
</Grid>

在后面的代码中，为集合视图源设置过滤器回调，

In code behind, set Filter callback for collection view source,

    private void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        var source = this.Resources["source"] as CollectionViewSource;
        source.Filter += source_Filter;
    }

    private void source_Filter(object sender, FilterEventArgs e)
    {
        if (((TableRecord) e.Item).State == RecordState.Deleted)
        {
            e.Accepted = false;
        }
        else
        {
            e.Accepted = true;
        }
    }

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