C#

<pre>

using Microsoft.Office.Interop.Excel;
using System;
using Excel = Microsoft.Office.Interop.Excel;

namespace ExcelTestConsoleApp1
{
    class Program
    {
        public static string filePath = @"f:\ExcelTest\Tst_Excel.xlsx";

        static void Main(string[] args)
        {
            CreateExcelFile();
            ReadExcelFile();
            Console.ReadLine();
        }

        private static void CreateExcelFile()
        {
            Excel.Application xlApp = new Excel.Application();


            if (xlApp == null)
            {
                Console.WriteLine("Excel is not installed on this system... ");
                return;
            }

            object misValue = System.Reflection.Missing.Value;

            Workbook xlWorkBook = xlApp.Workbooks.Add(misValue);
            Worksheet xlWorkSheet = (Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1);

            xlWorkSheet.Cells[1, 1] = "FirstName";
            xlWorkSheet.Cells[1, 2] = "LastName";
            xlWorkSheet.Cells[2, 1] = "Greg";
            xlWorkSheet.Cells[2, 2] = "Gonzales";

            xlWorkBook.SaveAs(filePath, XlFileFormat.xlExcel12, misValue, misValue, misValue, misValue,
            XlSaveAsAccessMode.xlExclusive, misValue, misValue, misValue, misValue);



            xlWorkBook.Close();
            xlApp.Quit();

            releaseObject(xlWorkSheet);
            releaseObject(xlWorkBook);
            releaseObject(xlApp);

            Console.BackgroundColor = ConsoleColor.DarkBlue;
            Console.WriteLine("Excel file created successfully... ");
            Console.BackgroundColor = ConsoleColor.Green;
            
            }

        private static void ReadExcelFile()
        {
            Console.BackgroundColor = ConsoleColor.DarkBlue;
            Console.WriteLine("\nReading the Excel File... ");
            Console.BackgroundColor = ConsoleColor.Green;

            Excel.Application xlApp = new Excel.Application();
            Excel.Workbook xlWorkBook = xlApp.Workbooks.Open(filePath);
            Excel.Worksheet xlWorkSheet = (Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1);

            Excel.Range xlRange = xlWorkSheet.UsedRange;
            int totalRows = xlRange.Rows.Count;
            int totalColumns = xlRange.Columns.Count;

            string firstValue, secondValue;

            for (int rowCount = 1; rowCount <= totalRows; rowCount++)
            {

                firstValue = Convert.ToString((xlRange.Cells[rowCount, 1] as Excel.Range).Text);
                secondValue = Convert.ToString((xlRange.Cells[rowCount, 2] as Excel.Range).Text);

                Console.WriteLine(firstValue + "\t" + secondValue);

            }

            xlWorkBook.Close();
            xlApp.Quit();

            releaseObject(xlWorkSheet);
            releaseObject(xlWorkBook);
            releaseObject(xlApp);

            Console.WriteLine("End of File... ");
        }

        private static void releaseObject(object obj)
        {
            try
            {
                System.Runtime.InteropServices.Marshal.ReleaseComObject(obj);
                obj = null;
            }
            catch (Exception ex)
            {
                obj = null;
                Console.WriteLine("Unable to release the Object " + ex.ToString());
            }
            finally
            {
                GC.Collect();
            }
        }
    }
}

xlWorkBook.SaveAs(filePath, XlFileFormat.xlExcel12, misValue, misValue, misValue, misValue,
XlSaveAsAccessMode.xlExclusive, misValue, misValue, misValue, misValue);

Every time I try to run this code I get this error… 
Exception Unhandled

System.Runtime.InteropServices.COMExceptions:'This extension can not be used with the selected file type. Change the file extension in the File name text box or select a different file type by changing the Save as type.'
<pre>

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

string htmltext = "my html string";
byte[] pdf = null;
var workStream = new MemoryStream();
using (var pdfWriter = new PdfWriter(workStream))
 {
   pdfWriter.SetCloseStream(false);

   using (var document = HtmlConverter.ConvertToDocument(htmltext, pdfWriter))
           {
              pdf = workStream.GetBuffer();
          }
   }
 workStream.Position = 0;
 return pdf; 

List<Rectangle>