DataGrid中如何通过Trigger等方式实现右键选中Cell

[saybookcat]

实现了一个DataGrid,选中时获得行和选中的单元格，通过右键菜单可以复制单元格的值，不过右键选中时 Cell不能被选中。
通过什么方式可以在xaml中实现右键选择cell时，先选中cell呢？

    <Window.Resources>
        <local:DataGridTextCellValueConverter x:Key="converter"/>

    </Window.Resources>
    
    <Window.DataContext>
        <local:MainViewModel/>
    </Window.DataContext>
    
    <DataGrid ItemsSource="{Binding Persons}"
              SelectedItem="{Binding CurrentRow}"
              CurrentCell="{Binding CurrentText, Mode=OneWayToSource, Converter={StaticResource converter}}"
              IsReadOnly="True"
              SelectionMode="Single">
        <DataGrid.ContextMenu>
            <ContextMenu>
                <MenuItem Header="Copy" Command="{Binding CopyCommand}" CommandParameter="{Binding CurrentText}"/>
            </ContextMenu>
        </DataGrid.ContextMenu>
    </DataGrid>

DataGridTextCellValueConverter

    public class DataGridTextCellValueConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            var cellInfo = (DataGridCellInfo)value;
            if (cellInfo==null || cellInfo.Column == null || cellInfo.Item == null) return string.Empty;
            var cellControl = cellInfo.Column.GetCellContent(cellInfo.Item);
            var textBlock = cellControl as TextBlock;
            if (textBlock == null) return string.Empty;
            return textBlock.Text;
        }
    }

引用了MvvmLight
MainViewModel

public class MainViewModel
    {
        public MainViewModel()
        {
            Persons = new ObservableCollection<PersonViewModel>();
            Persons.Add(new PersonViewModel { Name = "ssss", Age = 12 });
            Persons.Add(new PersonViewModel { Name = "xxxx", Age = 30 });
        }

        public ObservableCollection<PersonViewModel> Persons { get; set; }


        private PersonViewModel currentRow;
        public PersonViewModel CurrentRow
        {
            get
            {
                return currentRow;
            }
            set
            {
                currentRow = value;

                if (currentRow != null)
                {
                    Console.WriteLine("CurrentRow: Name = {0}, Age = {1} ",
                        currentRow.Name, currentRow.Age);
                }
            }
        }

        private string currentText;
        public string CurrentText
        {
            get
            {
                return currentText;
            }
            set
            {
                currentText = value;
                Console.WriteLine("CurrentText: " + currentText);
            }
        }

        private ICommand _copyCommand;
        public ICommand CopyCommand
        {
            get
            {
                if (_copyCommand == null)
                {
                    _copyCommand = new RelayCommand<string>(OnCopyAction);
                }
                return _copyCommand;
            }
        }

        private void OnCopyAction(string param)
        {
            if (string.IsNullOrWhiteSpace(param)) return;
            Clipboard.Clear();
            Clipboard.SetDataObject(param);
        }
    }

[郑州高新区WPF小王子]

右键点击的时候 DataGrid已经失去焦点，除非在数据类中手动增加一个选中属性，选择行的时候更改它的值为True，再根据Trigger判定它的值改变背景色。

[saybookcat]

SelectedItem 已经可以标记选中的是哪一行，这里主要的问题是 DataGrid SelectionUnit的问题 ，当前默认是CellOrRowHeader ，由于需要获得行 又获得列，只能设置这一种了。而在鼠标点击行的时候 Cell先被记录 ，然后 Row被记录 ，这时候由于 已经切换到Row选中模式，Cell选中将不被触发 。 我现在用了一种不太好的方式实现实现这部分功能。

            <i:Interaction.Triggers>
                <i:EventTrigger EventName="PreviewMouseRightButtonDown">
                    <command:EventToCommand Command="{Binding DataContext.SelectedCellItemCommand,
                        RelativeSource={RelativeSource AncestorType={x:Type DataGrid}}}" PassEventArgsToCommand="True"/>
                </i:EventTrigger>
            </i:Interaction.Triggers>

        private readonly ICommand _selectCellItemCommand = null;

        public ICommand SelectedCellItemCommand
        {
            get { return _selectCellItemCommand.Relay<RoutedEventArgs>(SelectedCellItemCmdAction); }
        }

        private void SelectedCellItemCmdAction(RoutedEventArgs e)
        {
            var dataGridCell = VisualUpwardSearch<DataGridCell>(e.OriginalSource as DependencyObject) as DataGridCell;

            if (dataGridCell == null) return;
            dataGridCell.Focus();
            e.Handled = true;
        }

[saybookcat]

补上

        private static DependencyObject VisualUpwardSearch<M>(DependencyObject source)
        {
            while (source != null && source.GetType() != typeof(M))
            {
                if (source is Visual || source is Visual3D)
                    source = VisualTreeHelper.GetParent(source);
                else
                    source = LogicalTreeHelper.GetParent(source);
            }
            return source;
        }