Npoi: We found a problem with some content (C#)

Question

I am using NPOI to generate excel file from Sql table. Everything works fine but when i tried to open the file it give me following error.

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Data.SqlClient;
using Microsoft.EntityFrameworkCore;
using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;
using System.Data;

namespace SfApi.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class SuccessfactorController : ControllerBase
    {
        private DataContext _context;
        private string sqlstring;

        public SuccessfactorController(DataContext context)
        {
            _context = context;
            //sqlstring will be use in each method in this controller with query
            sqlstring = _context.Database.GetConnectionString();
        }

        [HttpGet("GetSfResults")]
        public async Task<ActionResult<List<Successfactor>>> Get()
        {
            
            DataTable ds = new DataTable();
            using (SqlConnection con = new SqlConnection(sqlstring))
            {
                string query = "SELECT * FROM test";
                using (SqlCommand cmd = new SqlCommand(query))
                {
                    cmd.Connection = con;
                    using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
                    {
                        sda.Fill(ds);
                    }
                }
            }

            DataTable_To_Excel(ds, "D:\\ExcelTest\\ExcelTest.xlsx");

            return Ok(_context.Successfactor);
        }

Above code is getting data from Sql and filling it into data table.

private void DataTable_To_Excel(DataTable pDatos, string pFilePath)
{
    try
    {
        if (pDatos != null && pDatos.Rows.Count > 0)
        {
            IWorkbook workbook = null;
            ISheet worksheet = null;

            using (FileStream stream = new FileStream(pFilePath, FileMode.Create, FileAccess.Write))
            {
                string Ext = System.IO.Path.GetExtension(pFilePath); //<- File extension
                switch (Ext.ToLower())
                {
                    case ".xls":
                        HSSFWorkbook workbookH = new HSSFWorkbook();
                        NPOI.HPSF.DocumentSummaryInformation dsi = NPOI.HPSF.PropertySetFactory.CreateDocumentSummaryInformation();
                        dsi.Company = "Saskpolytech"; dsi.Manager = "Learning Technology";
                        workbookH.DocumentSummaryInformation = dsi;
                        workbook = workbookH;
                        break;

                    case ".xlsx": workbook = new XSSFWorkbook(); break;
                }

                //worksheet = workbook.CreateSheet(pDatos.TableName); //<- Use table name as Sheet name
                worksheet = workbook.CreateSheet("testSheetName"); //<- Use table name as Sheet name

                //FORMATS FOR CERTAIN TYPES OF DATA
                ICellStyle _TextCellStyle = workbook.CreateCellStyle();
                _TextCellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("text");

                ICellStyle _doubleCellStyle = workbook.CreateCellStyle();
                _doubleCellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("#,##0.###");

                ICellStyle _intCellStyle = workbook.CreateCellStyle();
                _intCellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("#,##0");

                ICellStyle _boolCellStyle = workbook.CreateCellStyle();
                _boolCellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("BOOLEAN");

                ICellStyle _dateCellStyle = workbook.CreateCellStyle();
                _dateCellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("dd-MM-yyyy");

                ICellStyle _dateTimeCellStyle = workbook.CreateCellStyle();
                _dateTimeCellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("dd-MM-yyyy HH:mm:ss");

                //REAR IN THE FIRST ROW THE TITLES OF THE COLUMNS
                int iRow = 0;
                if (pDatos.Columns.Count > 0)
                {
                    int iCol = 0;
                    IRow fila = worksheet.CreateRow(iRow);
                    foreach (DataColumn columna in pDatos.Columns)
                    {
                        ICell cell = fila.CreateCell(iCol, CellType.String);
                        cell.SetCellValue(columna.ColumnName);
                        cell.CellStyle = _TextCellStyle;
                        iCol++;
                    }
                    iRow++;
                }

                //NOW CREATE A ROW FOR EACH RECORD IN THE TABLE
                foreach (DataRow row in pDatos.Rows)
                {
                    IRow fila = worksheet.CreateRow(iRow);
                    int iCol = 0;
                    foreach (DataColumn column in pDatos.Columns)
                    {
                        ICell cell = null; //<-Represents the current cell                             
                        object cellValue = row[iCol]; //<- The current value of the cell

                        switch (column.DataType.ToString())
                        {
                            case "System.Boolean":
                                if (cellValue != DBNull.Value)
                                {
                                    cell = fila.CreateCell(iCol, CellType.Boolean);

                                    if (Convert.ToBoolean(cellValue)) { cell.SetCellFormula("TRUE()"); }
                                    else { cell.SetCellFormula("FALSE()"); }

                                    cell.CellStyle = _boolCellStyle;
                                }
                                break;

                            case "System.String":
                                if (cellValue != DBNull.Value)
                                {
                                    cell = fila.CreateCell(iCol, CellType.String);
                                    cell.SetCellValue (Convert.ToString(cellValue));
                                    cell.CellStyle = _TextCellStyle;
                                }
                                break;

                            case "System.Int32":
                                if (cellValue != DBNull.Value)
                                {
                                    cell = fila.CreateCell(iCol, CellType.Numeric);
                                    cell.SetCellValue(Convert.ToInt32(cellValue));
                                    cell.CellStyle = _intCellStyle;
                                }
                                break;
                            case "System.Int64":
                                if (cellValue != DBNull.Value)
                                {
                                    cell = fila.CreateCell(iCol, CellType.Numeric);
                                    cell.SetCellValue(Convert.ToInt64(cellValue));
                                    cell.CellStyle = _intCellStyle;
                                }
                                break;
                            case "System.Decimal":
                                if (cellValue != DBNull.Value)
                                {
                                    cell = fila.CreateCell(iCol, CellType.Numeric);
                                    cell.SetCellValue(Convert.ToDouble(cellValue));
                                    cell.CellStyle = _doubleCellStyle;
                                }
                                break;
                            case "System.Double":
                                if (cellValue != DBNull.Value)
                                {
                                    cell = fila.CreateCell(iCol, CellType.Numeric);
                                    cell.SetCellValue(Convert.ToDouble(cellValue));
                                    cell.CellStyle = _doubleCellStyle;
                                }
                                break;

                            case "System.DateTime":
                                if (cellValue != DBNull.Value)
                                {
                                    cell = fila.CreateCell(iCol, CellType.Numeric);
                                    cell.SetCellValue(Convert.ToDateTime(cellValue));

                                    //If there is no Time value, use dd-MM-yyyy format
                                    DateTime cDate = Convert.ToDateTime(cellValue);
                                    if (cDate != null && cDate.Hour > 0)
                                    {
                                        cell.CellStyle = _dateTimeCellStyle;
                                }
                                else { cell.CellStyle = _dateCellStyle; }
                        }
                                break;
                            default:
                                break;
                        }
                        iCol++;
                    }
                    iRow++;
                }

                workbook.Write(stream);
                
                stream.Close();
            }
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }
}

I have put lot of time in finding out answer, I can't find anything on internet. if some one can guide me would be great.

Answer 1

There is no pre-defined format called "BOOLEAN" so using it in your cellstyle invalidates the Excel Cell.

This line should be changed:

_boolCellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("BOOLEAN");

to

_boolCellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("General");

It is worth mentioning that if you click Yes on that dialog you screenshotted in your question, my Excel version reports what it repaired:

Repaired Records: Format from /xl/styles.xml part (Styles)

which can narrow your search drastically for finding the root cause.