1. 添加鼠标左键处理

AddHandler(DataGrid.MouseLeftButtonDownEvent, new RoutedEventHandler(grdStudyList_MouseLeftButtonDown), true);

2. 命中测试

 private void grdStudyList_MouseLeftButtonDown(object sender, RoutedEventArgs e)
        {
            Point CurrentPosition = System.Windows.Input.Mouse.GetPosition(grdStudyList);

            _hitResultsList.Clear();

            VisualTreeHelper.HitTest(grdStudyList, null,
                new HitTestResultCallback(DataGridHitTestResult),
                new PointHitTestParameters(CurrentPosition));

            if (0 >= _hitResultsList.Count)
            {
                return;
            }

            var element = _hitResultsList.Where(y => y.GetType() == typeof(DataGridHeaderBorder)
                || y.GetType() == typeof(ScrollViewer));

            bool isGridCell = true;
            foreach (var x in element)
            {
                isGridCell = false;
            }

            if (!isGridCell)
            {
                return;
            }
 
           //后续逻辑处理
        }


     //

private List<DependencyObject> _hitResultsList = new List<DependencyObject>();

 public HitTestResultBehavior DataGridHitTestResult(HitTestResult result)
        {
            // Set the behavior to return visuals at all z-order levels.

            if (3 > _hitResultsList.Count)
            {
                _hitResultsList.Add(result.VisualHit);

                return HitTestResultBehavior.Continue;
            }
            else
            {
                return HitTestResultBehavior.Stop;
            }
        }