NPOI Read Excel to DataTable

 //2018-5-18  Yuan Xin  NOPI
        public DataTable Excel_To_DataTable(string filepath, int sheetindex)
        {
            // --------------------------------- //
            /* REFERENCIAS:
             * NPOI.dll
             * NPOI.OOXML.dll
             * NPOI.OpenXml4Net.dll */
            // --------------------------------- //
            /* USING:
             * using NPOI.SS.UserModel;
             * using NPOI.HSSF.UserModel;
             * using NPOI.XSSF.UserModel; */
            // --------------------------------- //
            DataTable dt = null;
            try
            {
                if (System.IO.File.Exists(filepath))
                {

                    IWorkbook workbook = null;            
                    ISheet worksheet = null;
                    string first_sheet_name = "";

                    using (FileStream FS = new FileStream(filepath, FileMode.Open, FileAccess.Read))
                    {
                        workbook = WorkbookFactory.Create(FS); 
                        worksheet = workbook.GetSheetAt(sheetindex);
                        first_sheet_name = worksheet.SheetName;  

                        dt = new DataTable(first_sheet_name);
                        dt.Rows.Clear();
                        dt.Columns.Clear();

                        
                        for (int rowIndex = 0; rowIndex <= worksheet.LastRowNum; rowIndex++)
                        {
                            DataRow NewReg = null;
                            IRow row = worksheet.GetRow(rowIndex);
                            IRow row2 = null;

                            if (row != null) 
                            {
                                if (rowIndex > 0) NewReg = dt.NewRow();

                                
                                foreach (ICell cell in row.Cells)
                                {
                                    object valorCell = null;
                                    string cellType = "";

                                    if (rowIndex == 0) 
                                    {
                                        row2 = worksheet.GetRow(rowIndex + 1);
                                        if (row2 != null)
                                        {
                                            ICell cell2 = row2.GetCell(cell.ColumnIndex);
                                            if (cell2 != null)
                                            {
                                                switch (cell2.CellType)
                                                {
                                                    case CellType.Boolean: cellType = "System.Boolean"; break;
                                                    case CellType.String: cellType = "System.String"; break;
                                                    case CellType.Numeric:
                                                        if (HSSFDateUtil.IsCellDateFormatted(cell2)) { cellType = "System.DateTime"; }
                                                        else { cellType = "System.Double"; } break;
                                                    case CellType.Formula:
                                                        switch (cell2.CachedFormulaResultType)
                                                        {
                                                            case CellType.Boolean: cellType = "System.Boolean"; break;
                                                            case CellType.String: cellType = "System.String"; break;
                                                            case CellType.Numeric:
                                                                if (HSSFDateUtil.IsCellDateFormatted(cell2)) { cellType = "System.DateTime"; }
                                                                else { cellType = "System.Double"; } break;
                                                        }
                                                        break;
                                                    default:
                                                        cellType = "System.String"; break;
                                                }
                                                DataColumn dc = new DataColumn(cell.StringCellValue, System.Type.GetType(cellType));
                                                dt.Columns.Add(dc);
                                            }
                                            else 
                                            {
                                                DataColumn dc = new DataColumn("", typeof(string));
                                                dt.Columns.Add(dc);
                                            }


                                            
                                        }
                                    }
                                    else
                                    {

                                        if (cell == null)
                                        {
                                            continue;
                                        }
                                        else
                                        {
                                            switch (cell.CellType)
                                            {
                                                case CellType.Blank: valorCell = DBNull.Value; break;
                                                case CellType.Boolean: valorCell = cell.BooleanCellValue; break;
                                                case CellType.String: valorCell = cell.StringCellValue; break;
                                                case CellType.Numeric:
                                                    if (HSSFDateUtil.IsCellDateFormatted(cell)) { valorCell = cell.DateCellValue; }
                                                    else { valorCell = cell.NumericCellValue; } break;
                                                case CellType.Formula:
                                                    switch (cell.CachedFormulaResultType)
                                                    {
                                                        case CellType.Blank: valorCell = DBNull.Value; break;
                                                        case CellType.String: valorCell = cell.StringCellValue; break;
                                                        case CellType.Boolean: valorCell = cell.BooleanCellValue; break;
                                                        case CellType.Numeric:
                                                            if (HSSFDateUtil.IsCellDateFormatted(cell)) { valorCell = cell.DateCellValue; }
                                                            else { valorCell = cell.NumericCellValue; }
                                                            break;
                                                    }
                                                    break;
                                                default: valorCell = cell.StringCellValue; break;
                                            }
                                            NewReg[cell.ColumnIndex] = valorCell;
                                        }
                                    }
                                }
                            }
                            if (rowIndex > 0) dt.Rows.Add(NewReg);
                        }
                        dt.AcceptChanges();
                    }
                }
                else
                {
                    throw new Exception("ERROR 404:NO existe.");
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }
            return dt;
        }