Question

WPF DataGrid存在问题，这让我发疯。让我们考虑一下这个视图模型：

public class ViewModel : INotifyPropertyChanged
{
    public int Id { get; set; }
    public string Name { get; set; }

    public bool IsSelected 
    {
        get { return isSelected; }
        set
        {
            System.Diagnostics.Debug.WriteLine("{0}'s IsSelected new value is: {1}", Name, value);
            if (isSelected != value)
            {
                isSelected = value;
                OnPropertyChanged("IsSelected");
            }
        }
    }
    private bool isSelected;

    // INPC implementation
}

......这个XAML：

<Window x:Class="WpfApplication5.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <DataGrid ItemsSource="{Binding}" IsReadOnly="True" AutoGenerateColumns="False" 
                  SelectionMode="Extended" SelectionUnit="FullRow">
            <DataGrid.ItemContainerStyle>
                <Style TargetType="{x:Type DataGridRow}">
                    <Setter Property="IsSelected" Value="{Binding IsSelected}"/>
                </Style>
            </DataGrid.ItemContainerStyle>

            <DataGrid.Columns>
                <DataGridCheckBoxColumn Header="Is selected" Binding="{Binding IsSelected}"/>
                <DataGridTextColumn Header="Id" Binding="{Binding Id}"/>
                <DataGridTextColumn Header="Name" Width="*" Binding="{Binding Name}"/>
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>

...和这个代码隐藏：

public partial class MainWindow : Window
{
    private IList<ViewModel> GenerateViewModels()
    {
        var viewModels = new List<ViewModel>();

        for (var i = 0; i < 100; i++)
        {
            viewModels.Add(new ViewModel
            {
                Id = i,
                Name = string.Format("Item {0}", i)
            });
        }

        return viewModels;
    }

    public MainWindow()
    {
        InitializeComponent();
        DataContext = GenerateViewModels();
    }
}

案例1。

选择项目0.选择项目0，选中复选框。
滚动网格内容以隐藏项目0.让项目6位于可见区域的顶部。
选择项目10.选中项目10，选中复选框。
向上滚动至第0项。
选择项目0.选择项目10，复选框不选中。

调试输出：

Item 0's IsSelected new value is: True
Item 0's IsSelected new value is: False
Item 10's IsSelected new value is: True
Item 10's IsSelected new value is: False

Screenshot:

案例2。

重新启动应用程序。
在网格顶部选择多个项目（例如，三个第一项）。选中项目，选中复选框。
滚动网格内容以隐藏项目0.让项目6位于可见区域的顶部。
选择项目10.选中项目10，选中复选框。
向上滚动至第0项。
仍然检查项目0和项目1 。第2项未经检查。所有三个第一项都没有被选中。

调试输出：

Item 0's IsSelected new value is: True
Item 1's IsSelected new value is: True
Item 2's IsSelected new value is: True
Item 2's IsSelected new value is: False
Item 10's IsSelected new value is: True

Screenshot:

当选择模式延长时，问题是再现。当它是单身时，一切正常。

问题：
我错过了什么吗？ 2.有人知道解决方法吗？

更新

我已为网格添加了SelectionChanged事件处理程序：

    private void MyGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (e.AddedItems != null)
        {
            foreach (var item in e.AddedItems.Cast<ViewModel>())
            {
                System.Diagnostics.Debug.WriteLine("** Item {0} is added to selection.", item.Id);
            }
        }
        if (e.RemovedItems != null)
        {
            foreach (var item in e.RemovedItems.Cast<ViewModel>())
            {
                System.Diagnostics.Debug.WriteLine("** Item {0} is removed from selection.", item.Id);
            }
        }

        e.Handled = true;
    }

调试输出显示，SelectedItems集合已正确更新。例如，对于第一种情况输出将是：

Item 0's IsSelected new value is: True
** Item 0 is added to selection.
Item 0's IsSelected new value is: False
Item 10's IsSelected new value is: True
** Item 10 is added to selection.
** Item 0 is removed from selection.
Item 10's IsSelected new value is: False
** Item 0 is added to selection.
** Item 10 is removed from selection.

但绑定数据属性IsSelected未更新！

Answer 1

至少找到一个解决方法，它与问题的更新有关让我们稍微修改SelectionChanged事件处理程序：

    private void MyGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (e.AddedItems != null)
        {
            foreach (var item in e.AddedItems.Cast<ViewModel>())
            {
                System.Diagnostics.Debug.WriteLine("** Item {0} is added to selection.", item.Id);

                if (!item.IsSelected)
                {
                    // if bound data item still isn't selected, fix this
                    item.IsSelected = true;
                }
            }
        }
        if (e.RemovedItems != null)
        {
            foreach (var item in e.RemovedItems.Cast<ViewModel>())
            {
                System.Diagnostics.Debug.WriteLine("** Item {0} is removed from selection.", item.Id);

                if (item.IsSelected)
                {
                    // if bound data item still is selected, fix this
                    item.IsSelected = false;
                }
            }
        }

        e.Handled = true;
    }

但它绝对是DataGrid中的一个错误，不是吗？

Answer 2

我试过了，我认为你需要将isSelected设置为false以适应这两种情况。这个对我有用。但感谢最初的解决方案！它对我帮助很大。

private void MyGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (e.AddedItems != null)
        {
            foreach (var item in e.AddedItems.Cast<ViewModel>())
            {
                System.Diagnostics.Debug.WriteLine("** Item {0} is added to selection.", item.Id);

                if (!item.IsSelected)
                {
                    // if bound data item still isn't selected, fix this
                    item.IsSelected = false;
                }
            }
        }
        if (e.RemovedItems != null)
        {
            foreach (var item in e.RemovedItems.Cast<ViewModel>())
            {
                System.Diagnostics.Debug.WriteLine("** Item {0} is removed from selection.", item.Id);

                if (item.IsSelected)
                {
                    // if bound data item still is selected, fix this
                    item.IsSelected = false;
                }
            }
        }

        e.Handled = true;
    }

当SelectionMode =＆＃34; Extended＆＃34;时，DataGrid不会正确地取消选择隐藏的项目。

2 个答案: