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Tutorial: How to Implement Autoversioning with ASP.NET Master Pages

Example Master Page Markup
    <title>Your Website Title</title>
    <link rel="stylesheet" type="text/css" href="<% =auto_version("CSS/myStyle.css") %>" />
    <script type="text/javascript" language="javascript" src="<% =auto_version("js/myScript.js") %>"></script>
Code Behind Dependencies
using System.IO;
Master Page Code Behind
//appends a version number to the end of css and js files
protected string auto_version(string filename)
    //check if file exists
    string filepath = Server.MapPath("~/" + filename);
    if(!File.Exists( filepath ))
        return filename + "?ver=noexist";

    //get last modified date of file to use as version number
    DateTime madetime = File.GetLastWriteTime(filepath);
    string mtime = madetime.Month.ToString() + madetime.Day.ToString() + madetime.Year.ToString();

    //make filename relative to root directory
    filename = "/" + filename;

    //append version number to end of filename
    if (filepath.EndsWith(".css"))
        return filename.Replace(".css", ".css?ver=" + mtime);
    else if (filepath.EndsWith(".js"))
        return filename.Replace(".js", ".js?ver=" + mtime);
        return filename;

Published: September 17, 2011

Author's Note: CSS and JS file paths in the Master Page markup head section must be relative to the root directory without using a leading "/", "../", etc.