我正在使用 WPF 数据网格，并且具有 SelectionUnit="Cell" 和 SelectionMode="Extended"。我也在尽量遵守 MVVM 原则。
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，生活会很轻松。奇怪的是，SelectedCells 只引发一次 - 当我们第一次选择网格中的任何单元格时。
MS 在这里解释它：http://social.msdn.microsoft.com/Forums/en/wpf/thread/737117f4-6d20-4232-88cf-e52cc44d4431
谁能想到一种对 MVVM 友好的方法来解决它？
谢谢！
【问题讨论】：
我意识到我的最后一个答案是针对 SelectedItems 而不是 SelectedCells，所以我编写了一个完整的附加属性类来为多个 SelectedCells 进行数据绑定，其工作原理如下：
<controls:DataGrid ItemsSource="{StaticResource list}"
SelectionMode="Extended"
behaviors:DataGridSelectedCellsBehavior.SelectedCells="{Binding Path=SelectedGridCellCollection, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
我有一个工作源代码和它的演示项目here。
附加属性行为代码：
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;
}
【讨论】：
您需要 SelectedCells 不断地进行数据绑定，还是仅在用户点击 OK/Accept 按钮时才需要？例如，如果您只在用户所处的任何进程结束时才需要它，您可以将 SelectedCells 绑定到 Button 的 CommandParameter 属性。 SelectedCells 是一个 IList，您知道的足以对选择的实际对象类型进行强制转换。另一个选项更混乱，您可以使用附加属性，将事件处理排除在您的视图之外。此附加属性将处理 ListBox 或在您的情况下为 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);
}}}
在 XAML 中的用法：
<DataGrid ItemsSource="{Binding Path=SourceList}"
myControls:Attach.SelectedItems="{Binding Path=myMvvmSelectedItems, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
SelectionMode="Extended" />
【讨论】：
您可能对 WPF Application Framework (WAF) 的 BookLibrary 示例应用程序感兴趣。它展示了如何将 DataGrid.SelectedItems 与 ViewModel 同步。这可能与 SelectedCells 非常相似。
【讨论】：
SelectionChangedEvent 中的 ViewModel，而不是 ViewModel 属性和 @987654323 之间的数据绑定@ 财产。如果有人不想遵循过于严格的 MVVM 规则，这仍然很有用。
在完美的 MVVM 绑定和完整的事件处理程序代码隐藏之间的某个地方存在交互 EventTriggers 的灰色区域（请参阅 Blend SDK）:)
如果您将事件触发器放入数据网格，并设置为“SelectionChanged”并将事件参数传递给命令（使用 EventToCommand 动作触发器），您可以希望从事件参数中获取所选项目...
或者使用MS线程中所说的多重绑定:)
【讨论】：