Home » excel » c# – How to import large excel file to datatable?

c# – How to import large excel file to datatable?

Posted by: admin April 23, 2020 Leave a comment


I have an Excel file with 500 columns. I am using OLEDB to import it into a DataTable. But the DataTable contains only the first 255 columns. I can’t figure out why the rest of the columns aren’t imported.

My code is

public DataTable ToDataTable()
    DataSet dsEmpMaster = new DataSet();
    DataTable dtEmpMaster = null;
    string strConnectionString;
    string strSql;
    string FileNameWithPath = String.Format("{0}\{1}", System.IO.Path.GetDirectoryName(System.Diagnostics.Process.GetCurrentProcess().MainModule.FileName), _FileName);
        dtEmpMaster = new DataTable();

        strConnectionString = String.Format(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=Excel 12.0;", FileNameWithPath);
        strSql = String.Format("SELECT * FROM [{0}$]", _SheetName);
        OleDbDataAdapter adpMasterData = new OleDbDataAdapter(strSql, strConnectionString);
        dtEmpMaster = dsEmpMaster.Tables[0];
    catch (Exception ex)
        _ExcelError = ex.Message;
How to&Answers:

OLEDB cannot support >256 columns, see this for a workaround.

        var file_path = @"D:\doc\excel.xlsx";
        Microsoft.Office.Interop.Excel.Application xlApp =
            new Microsoft.Office.Interop.Excel.ApplicationClass();
        // Disabling messageboxes to prevent losing control on Excel app
        xlApp.DisplayAlerts = false;
        Microsoft.Office.Interop.Excel.Workbook xlWorkBook =
            xlApp.Workbooks.Open(file_path, 0, false, 5, "", "", true,
                Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);
        xlWorkBook.DoNotPromptForConvert = true;
        for (var k = 1; k <= xlWorkBook.Worksheets.Count; k++)
            Microsoft.Office.Interop.Excel.Worksheet xlWorkSheet =
                (Microsoft.Office.Interop.Excel.Worksheet) this.xlWorkBook.Worksheets.get_Item(k);
            int cCnt = xlWorkSheet.Cells.Count;
            // processing all cells used, but can call named ranges
            Microsoft.Office.Interop.Excel.Range range = xlWorkSheet.UsedRange;
            for (var rCnt = 1; rCnt <= range.Rows.Count; rCnt++)
                for (cCnt = 1; cCnt <= range.Columns.Count; cCnt++)
                    Microsoft.Office.Interop.Excel.Range rng =
                        (Microsoft.Office.Interop.Excel.Range) range.Cells[rCnt, cCnt];
                    // do something with range

But as mentioned in that thread Interop may be too slow for your needs, I personally havent used it but it might be worth looking at something like ExcelDataReader

edit: was fixing the formatting of the code from the link