xls to csv format

//css_reference ExcelLibrary.dll
using System;
using System.IO;
using ExcelLibrary.SpreadSheet;

/*
 * 엑셀 파일의 각 시트를 csv 포맷으로 바꾸어주는 C# 코드입니다.
 * CS-Script (http://www.csscript.net/) 사용
 * 사용된 dll 라이브러리
 * - ExcelLibrary.dll https://www.nuget.org/packages/ExcelLibrary/
 * 작성자 : CH Kim
 */

namespace Xls2Csv
{
    class Xls2Csv
    {
        public static void Main(string[] args)
        {
            if (args.Length != 1)
            {
                Console.WriteLine("Usage");
                Console.WriteLine("xls2csv <xls filename>");
                return;
            }

            Xls2Csv app = new Xls2Csv();
            app.convert(args[0]);
        }

        private int convert(string filename)
        {
            // gametable.xls 를 읽는다.
            try
            {
                FileStream fs = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite, 4096);
                Workbook workBook = Workbook.Load(fs);
                int sheetCount = workBook.Worksheets.Count;
                if (sheetCount < 1)
                    return 0;

                for (int i = 0; i < sheetCount; ++i)
                {
                    Worksheet sheet = workBook.Worksheets[i];

                    int rowIndex = 1;
                    int lastColIndex = sheet.Cells.LastColIndex;
                    int lastRowIndex = sheet.Cells.LastRowIndex;

                    Row row = sheet.Cells.GetRow(rowIndex++);
                    int rowCount = row.LastColIndex + 1;

                    string csvFilename = sheet.Name + ".csv";
                    StreamWriter file = new StreamWriter(csvFilename);

                    for (int n = 0; n < rowCount; ++n)
                    {
                        string text = row.GetCell(n).ToString();
                        if (n != 0)
                            file.Write(",");

                        file.Write(text);
                    }

                    file.WriteLine();

                    row = sheet.Cells.GetRow(rowIndex++);

                    for (int n = 0; n < rowCount; ++n)
                    {
                        string text = row.GetCell(n).ToString();
                        if (n != 0)
                            file.Write(",");

                        file.Write(text);
                    }

                    file.WriteLine();

                    for (int j = rowIndex; j <= lastRowIndex; ++j)
                    {
                        row = sheet.Cells.GetRow(j);
                        if (!row.GetCell(0).IsEmpty)
                        {
                            for (int n = 0; n < rowCount; ++n)
                            {
                                Cell cell = row.GetCell(n);
                                string text = cell.ToString();

                                if (n != 0)
                                    file.Write(",");

                                file.Write(text);
                            }

                            file.WriteLine();
                        }
                    }

                    file.Flush();
                    file.Close();

                    System.Console.WriteLine(csvFilename);

                } // end of sheet count

                fs.Close();
                return sheetCount;
            }

            catch (Exception ex)
            {
                System.Console.WriteLine(ex.ToString());
                return 0;
            }
        }
    }
}