C# - Excel Data Reader Library - Convert Excel (XLSX or XLS) to CSV

ExcelDataReader.cs

/*
 * Dependency : Excel Data Reader from http://exceldatareader.codeplex.com/
 * You must add the references to the Dlls (downloaded from the link above) with Visual Studio.
 */

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Excel;
using System.Data;
using System.IO;

namespace ExcelDataReaderTest
{
    class ExcelDataReader
    {
        static void Main(string[] args)
        {
            //Reading from a binary Excel file ('97-2003 format; *.xls)
            //IExcelDataReader excelReader2003 = ExcelReaderFactory.CreateBinaryReader(stream);
            
            //Reading from a OpenXml Excel file (2007 format; *.xlsx)
            FileStream stream = new FileStream("../../myxlsx/sample.xlsx", FileMode.Open);
            IExcelDataReader excelReader2007 = ExcelReaderFactory.CreateOpenXmlReader(stream);
            
            //DataSet - The result of each spreadsheet will be created in the result.Tables
            DataSet result = excelReader2007.AsDataSet();

            //Data Reader methods
            foreach (DataTable table in result.Tables)
            {
                for (int i = 0; i < table.Rows.Count; i++)
                {
                    for (int j = 0; j < table.Columns.Count; j++)
                        Console.Write("\"" + table.Rows[i].ItemArray[j] + "\";");
                    Console.WriteLine();
                }
            }

            //Free resources (IExcelDataReader is IDisposable)
            //excelReader2003.Close();
            excelReader2007.Close();
            Console.Read();
        }
    }
}

A detailed c# excel tutorial

http://csharp.net-informations.com/excel/csharp-excel-tutorial.htm

clint

Also check https://gist.github.com/Munawwar/924404.