如何使用 WPF 绑定触发 DataGrid 中特定单元格的更新

Question

我有一个自定义类，通过readonly 属性提供 3d 点信息：

public class Point3d
{
    private readonly double x;
    public double X { get { return x; } }

    private readonly double y;
    public double Y { get { return y; } }

    private readonly double z;
    public double Z { get { return z; } }

    public PoseCartesian(double x, double y, double z)
    {
        this.x = x;
        this.y = y;
        this.z = z;
    }
}

为了显示多个 3d 点，我在 WPF 中使用了带有四列的DataGrid。第一列应该显示条目的行号。

<DataGrid Name="dgrPoints" AutoGenerateColumns="False" 
    ItemsSource="{Binding UpdateSourceTrigger=Default, Mode=OneWay}"
    SelectionChanged="dgr_Poses_SelectionChanged" CanUserSortColumns="False"
    IsReadOnly="True">
    <DataGrid.Columns>
          <DataGridTextColumn x:Name="colI" Binding="{Binding Mode=OneWay,
               RelativeSource={RelativeSource AncestorType=DataGridRow},
               Converter={local:RowToIndexConverter}}"/>
          <DataGridTextColumn x:Name="colX" Binding="{Binding X}" Header="X"/>
          <DataGridTextColumn x:Name="colY" Binding="{Binding Y}" Header="Y"/>
          <DataGridTextColumn x:Name="colZ" Binding="{Binding Z}" Header="Z"/>
     </DataGrid.Columns>
</DataGrid>

要将点集合绑定到DataGrid，我使用ObservableCollection：

private ObservableCollection<Point3d> pointList;

通过设置DataContext结束绑定：

this.pointList = new ObservableCollection<Point3d>();
dgrPoints.ItemsSource= this.poseList;

要检索行号，我使用Andy 在此answer 中建议的以下转换器：

public class RowToIndexConverter : MarkupExtension, IValueConverter
{
    static RowToIndexConverter converter;

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        DataGridRow row = value as DataGridRow;
        if (row != null)
            return row.GetIndex() + 1;
        else
            return -1;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        if (converter == null) converter = new RowToIndexConverter();
        return converter;
    }

    public RowToIndexConverter()
    {
    }
}

这一切正常，并在添加新行 (Point3d) 时在 DataGrid 的第一列中设置相应的行号。但无论何时删除一行，行号都不会更新，因为转换器是通过添加新的DataGridRow 来触发的。现在我通过将DataGrid.DataContext 设置为null 来强制取消更新并再次添加：

this.pointList.RemoveAt(0);
dgrPoints.ItemsSource = null;
dgrPoints.ItemsSource = this.pointList;

这不是实现行号取消更新的正确解决方案。每当pointList 更改时，为每一行触发转换器的最佳方法是什么？

我不想使用DataGridRow.Header 属性，因为这会取代我的列。如果我错了，请纠正我。除此之外，我们欢迎所有考虑不同方法的建议。

Answer 1

您可以处理LoadingRow 和ItemContainerGenerator.ItemsChanged 事件并将DataGridRow 容器的Tag 属性设置为相应的行号：

public Window1()
{
    InitializeComponent();
    dgrPoints.ItemContainerGenerator.ItemsChanged += ItemContainerGenerator_ItemsChanged;
    dgrPoints.LoadingRow += DgrPoints_LoadingRow;
    dgrPoints.ItemsSource = ...;
}

private void DgrPoints_LoadingRow(object sender, DataGridRowEventArgs e)
{
    e.Row.Tag = (e.Row.GetIndex() + 1).ToString();
}

private void ItemContainerGenerator_ItemsChanged(object sender, ItemsChangedEventArgs e)
{
    IEnumerable<DataGridRow> rows = FindVisualChildren<DataGridRow>(dgrPoints);
    foreach (DataGridRow row in rows)
        row.Tag = (row.GetIndex() + 1).ToString();
}

private static IEnumerable<T> FindVisualChildren<T>(DependencyObject dependencyObject) where T : DependencyObject
{
    if (dependencyObject != null)
    {
        for (int i = 0; i < VisualTreeHelper.GetChildrenCount(dependencyObject); i++)
        {
            DependencyObject child = VisualTreeHelper.GetChild(dependencyObject, i);
            if (child != null && child is T)
            {
                yield return (T)child;
            }

            foreach (T childOfChild in FindVisualChildren<T>(child))
            {
                yield return childOfChild;
            }
        }
    }
}

---

<DataGrid Name="dgrPoints" AutoGenerateColumns="False" 
          ItemsSource="{Binding UpdateSourceTrigger=Default, Mode=OneWay}"
          CanUserSortColumns="False"
          IsReadOnly="True">
    <DataGrid.Columns>
        <DataGridTextColumn x:Name="colI" Binding="{Binding Path=Tag, Mode=OneWay, 
            RelativeSource={RelativeSource AncestorType=DataGridRow}}"/>
        <DataGridTextColumn x:Name="colX" Binding="{Binding X}" Header="X"/>
        <DataGridTextColumn x:Name="colY" Binding="{Binding Y}" Header="Y"/>
        <DataGridTextColumn x:Name="colZ" Binding="{Binding Z}" Header="Z"/>
    </DataGrid.Columns>
</DataGrid>