void UpdateCellNumber()
 {
     if (aux > 0)
     {//Si hay que actualizar el nº de la celda
         selectedCell.setNum(aux);
         //selectedCell.grid.Background = Brushes.Thistle;
         selectedCell.Solved = true;
         aux = -1;
     }
     else if (!selectedCell.Fixed && !selectedCell.Solved)
     {
         selectedCell.ShowPossibles();
     }
     //Marca como seleccionada
     Unselect();
     selectedCell.selected = true;
     selectedCell.SelectionChanged();
 }