How to sort data in excel in C# using NPOI library

Question

How do I sort data in an excel spreadsheet using C# and NPOI library?

The excel spreadsheet is very simple. There are two columns with header, "Name"(Column A) and "Birthday"(Column B). The data is in no way sorted.

My goal is to sort the list by alphabetical order by name. Of course, each Name should still matchup with the correct birthday.

How would I go about doing so?

Answer 1

Here is a working example. You'll need to modify it for your file as appropriate:

  // start by loading the workbook
  HSSFWorkbook workbook;
  using (var stream = new FileStream(@"c:\Temp\birthdays.xls", FileMode.Open))
  {
    var fs = new POIFSFileSystem(stream);
    workbook = new HSSFWorkbook(fs);
  }

  // now get the worksheet that has the birthdays; I am just using the first sheet
  var birthdaySheet = workbook.GetSheetAt(0);

  // we are going to populate a list of Birthday objects in memory that we can then sort and write back into the file;
  // the Birthday class is defined below
  var birthdays = new Collection<Birthday>();
  for (int i = 0; i < birthdaySheet.LastRowNum; i++) // the LastRowNum property is very useful!
  {
    birthdays.Add(new Birthday
                    {
                      Name = birthdaySheet.GetRow(i).GetCell(0).StringCellValue, // name is in column A, which is 0
                      Bday = birthdaySheet.GetRow(i).GetCell(1).NumericCellValue // birthday is in column B, which is 1
                    });
  }

  // now we sort the birthdays
  var sorted = birthdays.OrderBy(b => b.Name).ToArray();

  // now we go back through the cells and write over the values with the sorted values
  for (int i = 0; i < sorted.Length; i++)
  {
    birthdaySheet.GetRow(i).GetCell(0).SetCellValue(sorted[i].Name);
    birthdaySheet.GetRow(i).GetCell(1).SetCellValue(sorted[i].Bday);
  }

  // finally, save the workbook
  using (var stream = new FileStream(@"c:\temp\birthdays.xls", FileMode.Truncate))
  {
    workbook.Write(stream);
  }

The Birthday class:

class Birthday
{
  public string Name { get; set; }
  public double Bday { get; set; }
}