Cell index must be >= 0

var excelData = mapper.Take<CustomNpoiModel>(mapper.Workbook.GetSheetAt(0).SheetName).Select(x => x.Value).ToList();

I have used this line in 10 different “Actions” and every single approach this mapping works great, but in my last action I got this strange exception which is “Cell index must be >= 0” and the error does not provide any additional information!

Strangely, I have tried to use an Excel File which I’ve created last week, and when I use that File, I didn’t get any errors, then I simply copy that Excel file and create a new one, and copy those rows into the new Excel File, and yet I got the same error.

Additional Information :

public class CustomNpoiModel 
{
      [Column("No")]
      public int No { get; set; }
      
      [Column("Name")]
      public string Name { get; set; }
   
      [Column("Path")]
      public string Path { get; set; }
}

[donnytian]

But I will include more error details for any exception during import.

[donnytian]

ok, this property may mislead users to get the value after constructing a mapper. Actually it is initialized as -1 by design. The purpose of this property is to let user specify for the first row so the mapper can start to work from that row, even if there are non-blank rows above that index. for example you may have description rows at the beginning rows, and data rows just start after that.

public int FirstRowIndex { get; set; } = -1;

If you set it as zero explicitly, means there is no header row, the first row is data row already. if mapper see it’s -1 then mapper will use default value sheet.FirstRowNum.

private int GetFirstRowIndex(ISheet sheet) =>
    FirstRowIndex >= 0 ? FirstRowIndex : sheet.FirstRowNum;

I don’t see any issue with -1 as the default value, your exception may be related to the column index rather than the row index. Or may already been fixed 😃