MVVM DataGrid SelectedItem绑定未更新

Question

我是.Net和C#的新手,对绑定有点困惑.我有应用程序实现MVVM并显示DataGrid.我想要实现的是当用户按下某个键组合时,当前所选单元格的内容被复制到下面行中的单元格.我已经尝试将DataGrid的SelectedItem绑定到ViewModel属性,但它永远不会更新.CommandParameter也不起作用,项目计数始终为0.因此我无法提取用户选择的单元格,也无法读取所选单元格的内容.有没有人有如何解决这个问题或实现这个功能的建议？提前致谢.代码:xaml:

<DataGrid Grid.Row="1" 
          Grid.Column="0" 
          Grid.ColumnSpan="9" 
          AutoGenerateColumns="False" 
          Height="Auto" 
          HorizontalAlignment="Left" 
          Name="dataGrid" 
          VerticalAlignment="Top" 
          Width="{Binding ElementName=grid4,Path=Width}"
          ScrollViewer.CanContentScroll="False" 
          FrozenColumnCount="1" 
          SelectionUnit="Cell" 
          SelectionMode="Extended" 
          CanUserSortColumns = "False" 
          CanUserReorderColumns="False" 
          CanUserResizeRows="False" 
          RowHeight="25" 
          RowBackground="LightGray" 
          AlternatingRowBackground="White"
          ScrollViewer.VerticalScrollBarVisibility="Visible" 
          ScrollViewer.HorizontalScrollBarVisibility="Visible"
          ItemsSource="{Binding Layers, Mode=TwoWay}"  
          SelectedItem="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=DataContext.Selection, Mode=TwoWay}">
    <DataGrid.InputBindings>
        <KeyBinding Gesture="Shift" 
                    Command="{Binding ItemHandler}" 
                    CommandParameter="{Binding ElementName=dataGrid, Path=SelectedItems}">
        </KeyBinding>
    </DataGrid.InputBindings>
</DataGrid>

视图模型:

private float _selection = 0.0f;
    public float Selection
    {
        get
        {
            return _selection;
        }
        set
        {
            if (_selection != value)
            {
                _selection = value;
                NotifyPropertyChanged("Selection");
            }
        }
    }

...

        public DelegateCommand<IList> SelectionChangedCommand = new DelegateCommand<IList>(
        items =>
        {
            if (items == null)
            {
                NumberOfItemsSelected = 0; 
                return;
            }
            NumberOfItemsSelected = items.Count;
        });
    public ICommand ItemHandler
    {
        get
        {
            return SelectionChangedCommand;
        }
    }

Answer 1

编辑:SelectionUnit = Cell不使用SelectedItem

这是正常的mvvm方式:

首先是你想要在每一行显示的对象类型

 public class MyObject {}

第二个是包含集合和所选项目的视图模型

 public class MyViewmodel
 {
    public ObservableCollection<MyObject> MyItems {get;set;}
    public MyObject MySelectedItem {get;set;}

 }

xaml datagrid

 <DataGrid ItemsSource="{Binding MyItems}" SelectedItem="{Binding MySelectedItem, Mode=TwoWay}"/>

这就是你所拥有的.如果您现在想创建一个"复制"行的命令,您可以创建一个新对象MyObject并从MySelectedItem复制值,然后将新的MyObject添加到您的集合中.

但也许我没有把你的问题弄好.