Datagrid Selected Cells Row Index and Column Index into list.

Datagrid Selected Cells Row Index and Column Index into list. Using Attached Property. Huge Performance Issue.

 public class RowNumberDp
    {
        public static DependencyProperty DisplayRowNumberProperty =
            DependencyProperty.RegisterAttached("DisplayRowNumber",
                typeof(bool),
                typeof(RowNumberDp),
                new FrameworkPropertyMetadata(false, OnDisplayRowNumberChanged));

        public static bool GetDisplayRowNumber(DependencyObject target)
        {
            return (bool) target.GetValue(DisplayRowNumberProperty);
        }

        public static void SetDisplayRowNumber(DependencyObject target, bool value)
        {
            target.SetValue(DisplayRowNumberProperty, value);
        }

        private static void OnDisplayRowNumberChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)
        {
            if (!(target is DataGrid dataGrid)) return;       
            dataGrid.SelectedCellsChanged += Selectedcells;
        }

        private static void Selectedcells(object sender, SelectedCellsChangedEventArgs e)
        {
        
            if (!(sender is DataGrid datagrid)) return;           
            foreach (DataGridCellInfo obj in datagrid.SelectedCells)
            {
	    var rowIndex = datagrid.Items.IndexOf(obj.Item)
              var ColumnName = obj.Column.SortMemberPath;
            }           
               
        }      
        
    }

Problem Statement : Row Index is

causing huge performance Issue ...If I comment rowIndex  everything works Super Fast..

I need rowindex for SelectedCells.

I tried Different approach as well.

 1. 

     private static List<Tuple<int, int>> GetRowAndColumnIndicesFromGivenCell(DataGrid dataGrid, DataGridCell cell)
        {
            List<Tuple<int, int>> cellList = null;

            var columnIndex = cell.Column.DisplayIndex;
            var parent = VisualTreeHelper.GetParent(cell);
            while (parent != null && parent.GetType() != typeof(DataGridRow))
            {
                parent = VisualTreeHelper.GetParent(parent);
            }

            if (parent is DataGridRow)
            {
                var dataGridRow = parent as DataGridRow;
                var item = dataGridRow.Item;
                if (item != null)
                {
                    var rowIndex = dataGrid.Items.IndexOf(item);
                    if (rowIndex != -1)
                    {
                        cellList = new List<Tuple<int, int>>()
                        {
                            new Tuple<int, int>(rowIndex, columnIndex)
                        };
                    }
                }
            }

            return cellList;
        }

from above code...Only Visible Datagrid Rows will come....But Scrolling does not happen,

Example If i select 1 to 1000 Only 986 to 1000 Numbers will Show.