使用POI導入excel文件時讀取格式相關問題

在excel文檔中，數字、日期類型數據在編輯後會變成numeric格式

導致在讀取過程中，如果按照原來格式讀取會遇到問題

故添加以下函數進行判斷

        /// <summary>
        /// 獲取字符串格式的值
        /// </summary>
        /// <param name="cell"></param>
        /// <returns></returns>
        private string GetCellStringValue(ICell cell)
        {
            try
            {
                if (cell == null || cell.CellType == CellType.Blank)
                {
                    return null;
                }
                string result;
                switch (cell.CellType)
                {
                    case CellType.Numeric:
                        result = cell.NumericCellValue.ToString(CultureInfo.InvariantCulture);
                        break;
                    default:
                        result = cell.StringCellValue?.Trim();
                        break;
                }
                return result;
            }
            catch
            {
                return null;
            }
        }

        /// <summary>
        /// 獲取日期格式的值
        /// </summary>
        /// <param name="cell"></param>
        /// <returns></returns>
        private DateTime? GetCellDateTimeValue(ICell cell)
        {
            try
            {
                if (cell == null || cell.CellType == CellType.Blank)
                {
                    return null;
                }
                DateTime? result;
                switch (cell.CellType)
                {
                    case CellType.Numeric:
                        result = cell.DateCellValue;
                        break;
                    case CellType.String:
                        result = DateTime.Parse(cell.StringCellValue);
                        break;
                    default:
                        result = null;
                        break;
                }
                return result;
            }
            catch
            {
                return null;
            }
        }

        /// <summary>
        /// 獲取數字格式的值
        /// </summary>
        /// <param name="cell"></param>
        /// <returns></returns>
        private double? GetCellNumericValue(ICell cell)
        {
            try
            {
                if (cell == null || cell.CellType == CellType.Blank)
                {
                    return null;
                }
                double? result;
                switch (cell.CellType)
                {
                    case CellType.Numeric:
                        result = cell.NumericCellValue;
                        break;
                    case CellType.String:
                        result = double.Parse(cell.StringCellValue);
                        break;
                    default:
                        result = null;
                        break;
                }
                return result;
            }
            catch
            {
                return null;
            }
        }