Question

我正在使用WPF数据网格，并且SelectionUnit =“Cell”和SelectionMode =“Extended”。我也尽可能地坚持MVVM主体。

我需要我的ViewModel来跟踪当前的SelectedCells。

如果我可以将其SelectedCells属性绑定到我的ViewModel，那么生活将很容易。奇怪的是，当我们第一次选择网格中的任何单元格时，SelectedCells只会被提升一次。

MS在此解释：http://social.msdn.microsoft.com/Forums/en/wpf/thread/737117f4-6d20-4232-88cf-e52cc44d4431

有人能想到一种MVVM友好的解决方法吗？

谢谢！

Answer 1

我意识到我的最后一个答案是针对SelectedItems而不是SelectedCells，所以我写了一个完整的附加属性类来为多个SelectedCells做数据绑定，其工作原理如下：

 <controls:DataGrid ItemsSource="{StaticResource list}"
                      SelectionMode="Extended"
                      behaviors:DataGridSelectedCellsBehavior.SelectedCells="{Binding Path=SelectedGridCellCollection, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>

我有一个有效的源代码和一个演示项目here。

附加财产行为代码：

public class DataGridSelectedCellsBehavior
{
    // Source : https://archive.codeplex.com/?p=datagridthemesfromsl
    // Credit to : T. Webster, https://stackoverflow.com/users/266457/t-webster

    public static IList<DataGridCellInfo> GetSelectedCells(DependencyObject obj)
    {
        return (IList<DataGridCellInfo>)obj.GetValue(SelectedCellsProperty);
    }
    public static void SetSelectedCells(DependencyObject obj, IList<DataGridCellInfo> value)
    {
        obj.SetValue(SelectedCellsProperty, value);
    }

    public static readonly DependencyProperty SelectedCellsProperty = DependencyProperty.RegisterAttached("SelectedCells", typeof(IList<DataGridCellInfo>), typeof(DataGridSelectedCellsBehavior), new UIPropertyMetadata(null, OnSelectedCellsChanged));

    static SelectedCellsChangedEventHandler GetSelectionChangedHandler(DependencyObject obj)
    {
        return (SelectedCellsChangedEventHandler)obj.GetValue(SelectionChangedHandlerProperty);
    }
    static void SetSelectionChangedHandler(DependencyObject obj, SelectedCellsChangedEventHandler value)
    {
        obj.SetValue(SelectionChangedHandlerProperty, value);
    }

    static readonly DependencyProperty SelectionChangedHandlerProperty = DependencyProperty.RegisterAttached("SelectedCellsChangedEventHandler", typeof(SelectedCellsChangedEventHandler), typeof(DataGridSelectedCellsBehavior), new UIPropertyMetadata(null));

    //d is MultiSelector (d as ListBox not supported)
    static void OnSelectedCellsChanged(DependencyObject d, DependencyPropertyChangedEventArgs args)
    {
        if (GetSelectionChangedHandler(d) != null)
            return;

        if (d is DataGrid)//DataGrid
        {
            DataGrid datagrid = d as DataGrid;
            SelectedCellsChangedEventHandler selectionchanged = null;
            foreach (var selected in GetSelectedCells(d) as IList<DataGridCellInfo>)
                datagrid.SelectedCells.Add(selected);

            selectionchanged = (sender, e) =>
            {
                SetSelectedCells(d, datagrid.SelectedCells);
            };
            SetSelectionChangedHandler(d, selectionchanged);
            datagrid.SelectedCellsChanged += GetSelectionChangedHandler(d);
        }
        //else if (d is ListBox)
        //{
        //    ListBox listbox = d as ListBox;
        //    SelectionChangedEventHandler selectionchanged = null;

        //    selectionchanged = (sender, e) =>
        //    {
        //        SetSelectedCells(d, listbox.SelectedCells);
        //    };
        //    SetSelectionChangedHandler(d, selectionchanged);
        //    listbox.SelectionChanged += GetSelectionChangedHandler(d);
        //}
    }

}

查看型号代码：

class DemoViewModel : INotifyPropertyChanged
{  
    private IList<DataGridCellInfo> selectedGridCellCollection = new List<DataGridCellInfo>();
    public IList<DataGridCellInfo> SelectedGridCellCollection
    {
        get { return selectedGridCellCollection; }
        set
        {
            selectedGridCellCollection = value;
            NotifyPropertyChanged();
        }
    }

    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

Answer 2

您是否需要经常数据绑定的SelectedCells，或者只是当用户点击OK / Accept按钮时？例如，如果您在用户所处的任何进程结束时只需要它，则可以将SelectedCells绑定到Button的CommandParameter属性。 SelectedCells是一个IList，你知道只需要对选择实际上的任何对象类型进行强制转换。另一个选项比较混乱，您可以使用附加属性，将事件处理保留在视图之外。此附加属性将处理ListBox或在您的情况下处理DataGrid（MultiSelector）。

public class Attach 
{
    public static IList GetSelectedItems(DependencyObject obj)
    {
        return (IList)obj.GetValue(SelectedItemsProperty);
    }

    public static void SetSelectedItems(DependencyObject obj, IList value)
    {
        obj.SetValue(SelectedItemsProperty, value);
    }

    /// <summary>
    /// Attach this property to expose the read-only SelectedItems property of a MultiSelector for data binding.
    /// </summary>
    public static readonly DependencyProperty SelectedItemsProperty =
        DependencyProperty.RegisterAttached("SelectedItems", typeof(IList), typeof(Attach), new UIPropertyMetadata(new List<object>() as IList, OnSelectedItemsChanged));



    static SelectionChangedEventHandler GetSelectionChangedHandler(DependencyObject obj)
    {
        return (SelectionChangedEventHandler)obj.GetValue(SelectionChangedHandlerProperty);
    }
    static void SetSelectionChangedHandler(DependencyObject obj, SelectionChangedEventHandler value)
    {
        obj.SetValue(SelectionChangedHandlerProperty, value);
    }
    static readonly DependencyProperty SelectionChangedHandlerProperty =
        DependencyProperty.RegisterAttached("SelectionChangedHandler", typeof(SelectionChangedEventHandler), typeof(Attach), new UIPropertyMetadata(null));


    //d is MultiSelector (d as ListBox not supported)
    static void OnSelectedItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs args)
    {
        if (GetSelectionChangedHandler(d) != null)
            return;

        if (d is MultiSelector)//DataGrid
        {
            MultiSelector multiselector = d as MultiSelector;
            SelectionChangedEventHandler selectionchanged = null;
            foreach (var selected in GetSelectedItems(d) as IList)
                multiselector.SelectedItems.Add(selected);

            selectionchanged = (sender, e) =>
            {
                SetSelectedItems(d, multiselector.SelectedItems);
            };
            SetSelectionChangedHandler(d, selectionchanged);
            multiselector.SelectionChanged += GetSelectionChangedHandler(d);
        }
        else if (d is ListBox)
        {
            ListBox listbox = d as ListBox;
            SelectionChangedEventHandler selectionchanged = null;

            selectionchanged = (sender, e) =>
            {
                SetSelectedItems(d, listbox.SelectedItems);
            };
            SetSelectionChangedHandler(d, selectionchanged);
            listbox.SelectionChanged += GetSelectionChangedHandler(d);
        }}}

XAML中的用法：

<DataGrid ItemsSource="{Binding Path=SourceList}"
              myControls:Attach.SelectedItems="{Binding Path=myMvvmSelectedItems, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" 
              SelectionMode="Extended" />

Answer 3

您可能对 WPF Application Framework (WAF) 的 BookLibrary 示例应用感兴趣。它显示了如何将DataGrid.SelectedItems与ViewModel同步。这可能与SelectedCells非常相似。

Answer 4

完美的MVVM绑定和完整的事件处理程序代码隐藏之间存在交互性的灰色区域EventTriggers（请参阅Blend SDK）:)
如果你将一个eventtrigger放到datagrid，并设置为“SelectionChanged”并将eventargs传递给一个命令（使用EventToCommand actiontrigger），你可以从eventargs中获取所选的项目希望...
或者使用MS线程中所述的多重绑定：）

WPF Datagrid：将SelectedCells绑定到我的ViewModel的MVVM友好方式

4 个答案: