This article (PHP/.htaccess example) explains the idea behind it. Basically, you could append the timestamp of the last time you modified the file to the filename but still serve the original file. This way every time you save a new version of the CSS file, the filename will change which will force the browser to download the new version. This will work for many kinds of files, including both CSS and JS files. (An alternative to using the filename would be using the query string.)
A ASP.NET sample is this:
public static string GetBreaker(string fileName)
{
string cacheBreaker = null;
try
{
if (fileName.StartsWith("~"))
{
fileName = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, fileName.Remove(0));
}
cacheBreaker = File.GetLastWriteTime(fileName).ToFileTime().ToString();
}
catch { }
return string.IsNullOrEmpty(cacheBreaker) ? string.Empty : string.Format("?cachebreaker={0}", cacheBreaker);
}
And you call this method in your MasterPage in this way:
<link href="<%= this.ResolveClientUrl("~/CSS/style.css") %><%=CacheBreaker.GetBreaker("~/CSS/style.css") %>"
rel="stylesheet" type="text/css" />
