C#. xlsx date cell import to DataTable by NPOI 2.0

Question

I'm tried to convert .xlsx file to DataTable format by using NPOI 2.0 library. It's OK, but I have a problem with convert to string date cell. When I try to use construction like row.GetCell(j).ToString() - it's threw exception "Cannot get numeric value from a text cell". I tried to use DateCellValue property, but it also threw this exception. With other cell formats it's work good. Function, that I use it's:

private DataTable xlsxToDT(string fileName)
    {
        DataTable table = new DataTable();
        XSSFWorkbook workbook = new XSSFWorkbook(new FileStream(fileName, FileMode.Open, FileAccess.Read));
        ISheet sheet = workbook.GetSheetAt(0);
        IRow headerRow = sheet.GetRow(0);
        int cellCount = headerRow.LastCellNum;
        for (int i = headerRow.FirstCellNum; i < cellCount; i++)
        {
            DataColumn column = new DataColumn(headerRow.GetCell(i).StringCellValue);
            table.Columns.Add(column);
        }
        int rowCount = sheet.LastRowNum;
        for (int i = (sheet.FirstRowNum); i < sheet.LastRowNum; i++)
        {
            IRow row = sheet.GetRow(i);
            DataRow dataRow = table.NewRow();
            for (int j = row.FirstCellNum; j < cellCount; j++)
            {
                if (row.GetCell(j) != null)
                {
                    //EXCEPTION GENERATING IN THIS CODE
                    dataRow[j] = row.GetCell(j).ToString();
                    ////////////////////////////
                }
            }
            table.Rows.Add(dataRow);
        }
        workbook = null;
        sheet = null;
        return table;
    }

UPDATE: If I insert code like

row.GetCell(j).SetCellType(CellType.STRING);

in problem cell I have value like "36496.392581018517". Another cells converted correctly

Answer 1

Second column of your excel file has a date format (12/2/1999). This format is not recognized by NPOI in your current culture ("ru-RU"). This seems like a bug in NPOI, becuase when this happens, there is no way to read anything from that cell. The only way I came to, is to change the thread's culture before reading the excel file (and change it back after):

private DataTable xlsxToDT(string fileName)
{
    var prevCulture = Thread.CurrentThread.CurrentCulture;
    Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
    try
    {
        // Put your whole method body here.
    }
    finally
    {
        Thread.CurrentThread.CurrentCulture = prevCulture;
    }
}

Answer 2

ICell cell = row.GetCell(j);
if (cell != null)
{
    switch (cell.CellType)
    {
        case CellType.String:
            dataRow[j] = cell.StringCellValue;
            break;
        case CellType.Numeric:
            dataRow[j] = cell.NumericCellValue;
            break;
        case CellType.Boolean:
            dataRow[j] = cell.BooleanCellValue;
            break;
        default: dataRow[j] = "ERROR";
            break;
    }
}

Answer 3

My solution is create function getValue like this

FileStream fs = new FileStream(@"\export.xlsx", FileMode.Open);
XSSFWorkbook wb = new XSSFWorkbook(fs);
ISheet sheet = wb.GetSheetAt(0);
// GetValue here
string text = getValueFromCell(sheet.GetRow(row).GetCell(1));

public string getValueFromCell(ICell cell) {
            string output ="";
            if (cell != null)
            {
                switch (cell.CellType)
                {
                    case CellType.String:
                        output = cell.StringCellValue;
                        break;
                    case CellType.Numeric:
                        //dataRow[j] = cell.NumericCellValue;
                        output = cell.NumericCellValue.ToString();
                        break;
                    case CellType.Boolean:
                        output = cell.BooleanCellValue.ToString();
                        //dataRow[j] = cell.BooleanCellValue;
                        break;
                    default:
                        output = "";
                        break;
                }
            }
            return output;
        }

Answer 4

This is correct code for xls

public DataTable GetDataTableFromExcelFile(string excel_file_Path)
{
    HSSFWorkbook wb;
    NPOI.SS.UserModel.ISheet sh;
    string Sheet_name;

    using (var fs = new FileStream(excel_file_Path, FileMode.Open, FileAccess.Read))
    {
        wb = new HSSFWorkbook(fs);

        Sheet_name = wb.GetSheetAt(0).SheetName;  //get first sheet name
    }
    DataTable DT = new DataTable();
    DT.Rows.Clear();
    DT.Columns.Clear();

    // get sheet
    sh = wb.GetSheet(Sheet_name);

    // add neccessary columns
    if (DT.Columns.Count < sh.GetRow(0).Cells.Count)
    {
        for (int j = 0; j < sh.GetRow(0).Cells.Count; j++)
        {
            DT.Columns.Add(Convert.ToString(sh.GetRow(0).Cells[j]), typeof(string));
        }
    }

    // add row
    DT.Rows.Add();

    int i = 1;
    while (sh.GetRow(i) != null)
    {
        // write row value
        for (int j = 0; j < sh.GetRow(i).Cells.Count; j++)
        {
            var cell = sh.GetRow(i).GetCell(j);

            if (cell != null)
            {
                // TODO: you can add more cell types capatibility, e. g. formula
                switch (cell.CellType)
                {
                    case CellType.Numeric:
                        DT.Rows[i][j] = sh.GetRow(i).GetCell(j).NumericCellValue;
                        //dataGridView1[j, i].Value = sh.GetRow(i).GetCell(j).NumericCellValue;

                        break;
                    case CellType.String:
                        DT.Rows[i-1][j] = sh.GetRow(i).GetCell(j).StringCellValue;

                        break;
                }
            }
        }

        i++;
    }

    return DT;
}