public async Task AddCellAsync(Cell cell)
 {
     if (cell.Value != null && cell.Value != string.Empty)
     {
         _cellRepository.Add(cell);
         await _unitOfWork.SaveChangesAsync();
     }
 }
        public async Task ModifyCellAsync(Cell cell)
        {
            _cellRepository.Attach(cell);
            var entry = _unitOfWork.Entry(cell);

            if (cell.Value != null && cell.Value != string.Empty)
            {
                await this.SaveCellAsync(entry);
            }
            else
            {
                await this.RemoveCellAsync(entry);
            }
        }