wpf - 如何按显示的转换值而不是绑定(bind)的源属性值对 DataGridTextColumn 进行排序？

Question

如何按显示的、转换的值而不是绑定(bind)的源属性值对 WPF DataGridTextColumn 进行排序？现在它按行 View 模型中的整数值排序，而不是显示转换器返回的文本。我使用 MVVM。

这是一个请求的例子。然而，这是一般性问题。我可以将 MmsClass.Name 放在代表该行的类中。但我需要在所有地方进行适当的排序，而不仅仅是这里。

一行的类:

public class MaintenanceDataItem
{
    public MaintenanceDataItem(int classId, Type objectType, object value, IEnumerable<MmsData> rows)
    {
        ClassId = classId;
        TypeOfObject = objectType;
        Value = value;
        ObjectIds = new List<int>();
        MmsDataRows = rows;
    }

    public int ClassId { get; private set; }
    // rest of the properrties omitted
}

转换器:

public class MmsClassToNameConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        MmsClass mmsClass;
        if (MmsClasses.Instance.TryGetValue((int) value, out mmsClass))
        {
            return mmsClass.Name;
        }
        return value.ToString();
    }

    public object ConvertBack(object value, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        return value.Equals(true) ? parameter : Binding.DoNothing;
    }
}

xaml 中的列:

            <DataGridTextColumn Header="{StaticResource ResourceKey=MmsStrCondClass}" Binding="{Binding ClassId, Converter={StaticResource mmsclasstonameconverter}}" Width="*">
                <DataGridTextColumn.ElementStyle>
                    <Style TargetType="{x:Type TextBlock}"
                        BasedOn="{StaticResource {x:Type TextBlock}}">
                        <Setter Property="TextWrapping" Value="NoWrap" />
                        <Setter Property="TextTrimming" Value="CharacterEllipsis"/>
                    </Style>
                </DataGridTextColumn.ElementStyle>
            </DataGridTextColumn>

我真的以为默认排序会显示值。如果这不容易解决，那么使用转换器对于 datagridcolumn 就没有多大意义。

Answer 1

不幸的是，这不是一项微不足道的任务。正如@Maverik 正确指出的那样，DataGrid 对基础数据进行排序，而不是转换器吐出的内容。为此，您需要自己排序。首先创建一个类，其中包含一个属性以使用您的自定义排序器，另一个类用于定义要在给定列上使用的排序器:

    public static ICustomSorter GetCustomSorter(DependencyObject obj)
    {
        return (ICustomSorter)obj.GetValue(CustomSorterProperty);
    }

    public static void SetCustomSorter(DependencyObject obj, ICustomSorter value)
    {
        obj.SetValue(CustomSorterProperty, value);
    }

    // Using a DependencyProperty as the backing store for CustomSorter.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty CustomSorterProperty =
        DependencyProperty.RegisterAttached("CustomSorter", typeof(ICustomSorter), typeof(CustomSortBehavior), new PropertyMetadata(null));

    public static bool GetAllowCustomSort(DependencyObject obj)
    {
        return (bool)obj.GetValue(AllowCustomSortProperty);
    }

    public static void SetAllowCustomSort(DependencyObject obj, bool value)
    {
        obj.SetValue(AllowCustomSortProperty, value);
    }

    // Using a DependencyProperty as the backing store for AllowCustomSort.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty AllowCustomSortProperty =
        DependencyProperty.RegisterAttached("AllowCustomSort", typeof(bool), typeof(CustomSortBehavior), new PropertyMetadata(false, AllowCustomSortChanged));

ICustomSorter 是一个非常简单的接口(interface):

public interface ICustomSorter : IComparer
{
    ListSortDirection SortDirection { get; set; }

    string SortMemberPath { get; set; }
}

现在您需要从“AllowCustomSort”实现自定义排序:

    private static void AllowCustomSortChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        DataGrid control = d as DataGrid;
        {
            var oldAllow = (bool)e.OldValue;
            var newAllow = (bool)e.NewValue;

            if (!oldAllow && newAllow)
            {
                control.Sorting += HandleCustomSorting;
            }
            else
            {
                control.Sorting -= HandleCustomSorting;
            }
        }
    }

    private static void HandleCustomSorting(object sender, DataGridSortingEventArgs e)
    {
        //Check if we should even be using custom sorting
        DataGrid dataGrid = sender as DataGrid;
        if (dataGrid != null && GetAllowCustomSort(dataGrid))
        {
            //Make sure we have a source we can sort
            ListCollectionView itemsSource = dataGrid.ItemsSource as ListCollectionView;
            if (itemsSource != null)
            {
                ICustomSorter columnSorter = GetCustomSorter(e.Column);

                //Only do our own sort if a sorter was defined
                if (columnSorter != null)
                {
                    ListSortDirection nextSortDirection = e.Column.SortDirection == ListSortDirection.Ascending ?
                                                          ListSortDirection.Descending :
                                                          ListSortDirection.Ascending;
                    e.Column.SortDirection = columnSorter.SortDirection = nextSortDirection;
                    columnSorter.SortMemberPath = e.Column.SortMemberPath;
                    itemsSource.CustomSort = columnSorter;

                    //We've handled the sort, don't let the DataGrid mess with us
                    e.Handled = true;
                }
            }
        }
    }

这只是连接 Sorting 事件，然后通过调用提供的 ICustomSorter 对集合进行排序来处理它。

在您的 XAML 中，您创建一个已实现的 ICustomSorter 的实例并使用附加属性，如下所示:

            <DataGridTextColumn Header="Column1" Binding="{Binding Column1, Converter={StaticResource Column1Converter}}" IsReadOnly="True"
                                util:CustomSortBehavior.CustomSorter="{StaticResource Column1Comparer}"/>

这很痛苦，您必须对所有转换后的值进行自定义排序，但它确实允许您在 DataGrid 中执行此操作。