在选项卡控件中处理多个数据网格以便单元格在选项卡更改时离开编辑模式的正确方法是什么？

Question

在 wpf 中，我设置了一个选项卡控件，该控件绑定到对象集合，每个对象都有一个数据模板，其中包含显示数据的数据网格。如果我选择一个特定的单元格并将其置于编辑模式，通过转到另一个选项卡来离开网格，这将导致在返回数据网格时引发以下异常：

在 AddNew 或 EditItem 事务期间不允许“DeferRefresh”。

该单元格似乎从未离开过编辑模式。有没有一种简单的方法可以使单元格退出编辑模式，或者这里发生了其他事情？

更新：看起来，如果我不将选项卡控件绑定到数据源，而是显式定义每个选项卡，然后将数据源中的每个项目绑定到内容控件，那么这个问题就会消失。这并不是一个很好的解决方案，所以我仍然想知道如何将集合直接绑定到选项卡控件。

更新：因此，我实际上为自己的解决方案所做的是使用 ListView 和内容控件来代替选项卡控件。我使用一种样式使列表视图看起来像选项卡。视图模型公开一组子视图模型，并允许用户通过列表视图选择一个。然后，内容控件呈现选定的视图模型，每个视图模型都有一个包含数据网格的关联数据模板。通过此设置，在网格上处于编辑模式时在视图模型之间切换将正确结束编辑模式并保存数据。

这是用于设置此功能的 xaml：

<ListView ItemTemplate="{StaticResource MakeItemsLookLikeTabs}" 
          ItemsSource="{Binding ViewModels}"  
          SelectedItem="{Binding Selected}" 
          Style="{StaticResource MakeItLookLikeATabControl}"/>

<ContentControl Content="{Binding Selected}">

我会接受 Phil 的答案，因为这也应该有效，但对我来说，上面的解决方案似乎在项目之间更易于移植。

Answer 1

我根据在 这个线程。

用法：

代码：

using System.Collections.Generic;
using System.Reflection;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Input;
using System.Windows.Media;

/// <summary>
///   Provides an ugly hack to prevent a bug in the data grid.
///   https://connect.microsoft.com/VisualStudio/feedback/details/532494/wpf-datagrid-and-tabcontrol-deferrefresh-exception
/// </summary>
public class DataGridCommitEditBehavior
{
    public static readonly DependencyProperty CommitOnLostFocusProperty =
        DependencyProperty.RegisterAttached(
            "CommitOnLostFocus", 
            typeof(bool), 
            typeof(DataGridCommitEditBehavior), 
            new UIPropertyMetadata(false, OnCommitOnLostFocusChanged));

    /// <summary>
    ///   A hack to find the data grid in the event handler of the tab control.
    /// </summary>
    private static readonly Dictionary<TabPanel, DataGrid> ControlMap = new Dictionary<TabPanel, DataGrid>();

    public static bool GetCommitOnLostFocus(DataGrid datagrid)
    {
        return (bool)datagrid.GetValue(CommitOnLostFocusProperty);
    }

    public static void SetCommitOnLostFocus(DataGrid datagrid, bool value)
    {
        datagrid.SetValue(CommitOnLostFocusProperty, value);
    }

    private static void CommitEdit(DataGrid dataGrid)
    {
        dataGrid.CommitEdit(DataGridEditingUnit.Cell, true);
        dataGrid.CommitEdit(DataGridEditingUnit.Row, true);
    }

    private static DataGrid GetParentDatagrid(UIElement element)
    {
        UIElement childElement; // element from which to start the tree navigation, looking for a Datagrid parent

        if (element is ComboBoxItem)
        {
            // Since ComboBoxItem.Parent is null, we must pass through ItemsPresenter in order to get the parent ComboBox
            var parentItemsPresenter = VisualTreeFinder.FindParentControl<ItemsPresenter>(element as ComboBoxItem);
            var combobox = parentItemsPresenter.TemplatedParent as ComboBox;
            childElement = combobox;
        }
        else
        {
            childElement = element;
        }

        var parentDatagrid = VisualTreeFinder.FindParentControl<DataGrid>(childElement);
        return parentDatagrid;
    }

    private static TabPanel GetTabPanel(TabControl tabControl)
    {
        return
            (TabPanel)
                tabControl.GetType().InvokeMember(
                    "ItemsHost", 
                    BindingFlags.NonPublic | BindingFlags.GetProperty | BindingFlags.Instance, 
                    null, 
                    tabControl, 
                    null);
    }

    private static void OnCommitOnLostFocusChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs e)
    {
        var dataGrid = depObj as DataGrid;
        if (dataGrid == null)
        {
            return;
        }

        if (e.NewValue is bool == false)
        {
            return;
        }

        var parentTabControl = VisualTreeFinder.FindParentControl<TabControl>(dataGrid);
        var tabPanel = GetTabPanel(parentTabControl);
        if (tabPanel != null)
        {
            ControlMap[tabPanel] = dataGrid;
        }

        if ((bool)e.NewValue)
        {
            // Attach event handlers
            if (parentTabControl != null)
            {
                tabPanel.PreviewMouseLeftButtonDown += OnParentTabControlPreviewMouseLeftButtonDown;
            }

            dataGrid.LostKeyboardFocus += OnDataGridLostFocus;
            dataGrid.DataContextChanged += OnDataGridDataContextChanged;
            dataGrid.IsVisibleChanged += OnDataGridIsVisibleChanged;
        }
        else
        {
            // Detach event handlers
            if (parentTabControl != null)
            {
                tabPanel.PreviewMouseLeftButtonDown -= OnParentTabControlPreviewMouseLeftButtonDown;
            }

            dataGrid.LostKeyboardFocus -= OnDataGridLostFocus;
            dataGrid.DataContextChanged -= OnDataGridDataContextChanged;
            dataGrid.IsVisibleChanged -= OnDataGridIsVisibleChanged;
        }
    }

    private static void OnDataGridDataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
        var dataGrid = (DataGrid)sender;
        CommitEdit(dataGrid);
    }

    private static void OnDataGridIsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
        var senderDatagrid = (DataGrid)sender;

        if ((bool)e.NewValue == false)
        {
            CommitEdit(senderDatagrid);
        }
    }

    private static void OnDataGridLostFocus(object sender, KeyboardFocusChangedEventArgs e)
    {
        var dataGrid = (DataGrid)sender;

        var focusedElement = Keyboard.FocusedElement as UIElement;
        if (focusedElement == null)
        {
            return;
        }

        var focusedDatagrid = GetParentDatagrid(focusedElement);

        // Let's see if the new focused element is inside a datagrid
        if (focusedDatagrid == dataGrid)
        {
            // If the new focused element is inside the same datagrid, then we don't need to do anything;
            // this happens, for instance, when we enter in edit-mode: the DataGrid element loses keyboard-focus, 
            // which passes to the selected DataGridCell child
            return;
        }

        CommitEdit(dataGrid);
    }

    private static void OnParentTabControlPreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        var dataGrid = ControlMap[(TabPanel)sender];
        CommitEdit(dataGrid);
    }
}

public static class VisualTreeFinder
{
    /// <summary>
    ///   Find a specific parent object type in the visual tree
    /// </summary>
    public static T FindParentControl<T>(DependencyObject outerDepObj) where T : DependencyObject
    {
        var dObj = VisualTreeHelper.GetParent(outerDepObj);
        if (dObj == null)
        {
            return null;
        }

        if (dObj is T)
        {
            return dObj as T;
        }

        while ((dObj = VisualTreeHelper.GetParent(dObj)) != null)
        {
            if (dObj is T)
            {
                return dObj as T;
            }
        }

        return null;
    }
}

Answer 2

我已经成功解决了这个问题，方法是检测用户何时单击 TabItem，然后在 TabControl 中的可见 DataGrid 上提交编辑。我假设用户希望当他们点击返回时他们的更改仍然存在。

代码片段：

// PreviewMouseDown event handler on the TabControl
private void TabControl_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
    if (IsUnderTabHeader(e.OriginalSource as DependencyObject))
        CommitTables(yourTabControl);
}

private bool IsUnderTabHeader(DependencyObject control)
{
    if (control is TabItem)
        return true;
    DependencyObject parent = VisualTreeHelper.GetParent(control);
    if (parent == null)
        return false;
    return IsUnderTabHeader(parent);
}

private void CommitTables(DependencyObject control)
{
    if (control is DataGrid)
    {
        DataGrid grid = control as DataGrid;
        grid.CommitEdit(DataGridEditingUnit.Row, true);
        return;
    }
    int childrenCount = VisualTreeHelper.GetChildrenCount(control);
    for (int childIndex = 0; childIndex < childrenCount; childIndex++)
        CommitTables(VisualTreeHelper.GetChild(control, childIndex));
}

这是在后面的代码中。

Answer 3

此错误在 .NET Framework 4.5 中已得到解决。您可以通过此链接下载它。

Answer 4

我认为你应该做的与@myermian 所说的非常接近。
有一个名为 CellEditEnding end 的事件，该事件允许您拦截并决定删除不需要的行。

private void dataGrid1_CellEditEnding(object sender, DataGridCellEditEndingEventArgs e)
    {
        DataGrid grid = (DataGrid)sender;
        TextBox cell = (TextBox)e.EditingElement;
        if(String.IsNullOrEmpty(cell.Text) && e.EditAction == DataGridEditAction.Commit)
        {
            grid.CancelEdit(DataGridEditingUnit.Row);
            e.Cancel = true;
        }            
    }