Generating vCalendar files (.vcs) to download in ASP.NET

Introduction

Very simple to create vCalendar files, it is basically like creating text files, the only difference is the format.

In this example, a physical file is not created (no need to clean up a temp directory afterwards), the file is kept in memory using memory stream. Once the file is created in memory, it is sent for download.

vCalendar is using UTC, so the function ToUniversalTime is used to convert the local time to UTC.

<%@ Page Language="vb" ContentType="text/html" 
    ResponseEncoding="iso-8859-1" Debug="False" trace="False"%>
<%@ import Namespace="System.IO" %>

<script runat="server"> 
Sub Page_Load(Sender As Object, E As EventArgs) 

 'PARAMETERS

   Dim beginDate as Date = #01/07/2005 4:00 PM#

   Dim endDate as Date  = #01/07/2005 6:00 PM#
   Dim myLocation as String = "Computer Room"
   Dim mySubject as String = "Training"
   Dim myDescription as String = "Event details" 
 'INITIALIZATION

   Dim mStream As new MemoryStream()
   Dim writer As new StreamWriter(mStream)
   writer.AutoFlush = true 
 'HEADER

   writer.WriteLine("BEGIN:VCALENDAR")
   writer.WriteLine("PRODID:-//Flo Inc.//FloSoft//EN")
   writer.WriteLine("BEGIN:VEVENT") 
 'BODY

   writer.WriteLine("DTSTART:" & _
            beginDate.ToUniversalTime.ToString("yyyyMMdd\THHmmss\Z") )
   writer.WriteLine("DTEND:" & _
           endDate.ToUniversalTime.ToString("yyyyMMdd\THHmmss\Z") )
   writer.WriteLine("LOCATION:" & myLocation)
   writer.WriteLine("DESCRIPTION;ENCODING=QUOTED-PRINTABLE:" & myDescription)
   writer.WriteLine("SUMMARY:" & mySubject) 
 'FOOTER

   writer.WriteLine("PRIORITY:3")
   writer.WriteLine("END:VEVENT")
   writer.WriteLine("END:VCALENDAR") 
 'MAKE IT DOWNLOADABLE

   Response.Clear() 'clears the current output content from the buffer

   Response.AppendHeader("Content-Disposition", _
            "attachment; filename=Add2Calendar.vcs")
   Response.AppendHeader("Content-Length", mStream.Length.ToString())
   Response.ContentType = "application/download"
   Response.BinaryWrite(mStream.ToArray())
   Response.End() 
End Sub
</script>