I implemented a behavior for the DataGrid based on code I found in this thread.
Usage:<DataGrid local:DataGridCommitEditBehavior.CommitOnLostFocus="True" />
Code:
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;
}
}