Static File Browser Caching for ASP.NET Web Forms Application

Question

We want browser caching on the content from certain folders on the site (images / styles / scripts) and setting them to remain fresh for 7 days. Also, we use a CMS called Ektron.

Here is the code we were using, any ideas as to why this isn't working?

From global.asax

void Application_PreSendRequestHeaders(object sender, EventArgs e)
{
    System.Web.HttpCacheability cachelevel = System.Web.HttpCacheability.Private;

    if (Request.FilePath.ToLower().StartsWith("/images") || Request.FilePath.ToLower().StartsWith("/styles") || 
        Request.FilePath.ToLower().StartsWith("/js") || Request.FilePath.ToLower().StartsWith("/scripts"))
    {
        cachelevel = System.Web.HttpCacheability.Public;

        if (cachelevel == System.Web.HttpCacheability.Public) Response.Cache.SetCacheability(cachelevel);

        var staticExtensions = new List<string> { ".js", ".css", ".jpg", ".gif", ".png" };

        if (staticExtensions.Any(ext => Request.FilePath.ToLower().EndsWith(ext)))
        {
            Response.Cache.SetMaxAge(TimeSpan.FromDays(7));
        }
    }

The content is not being cached, there's no difference in the headers, and everything is still set with maxage=0 and cache control is private. I believe it should be set as public and the max age=604800. — Andy Jr.
– Andy Jr., Commented Sep 26, 2016 at 21:39

Robert Benyi · Accepted Answer · 2020-02-26 11:13:27Z

2

Don't think Application_PreSendRequestHeaders will not fire for every static content. Instead use the Web.config system.webServer - staticContent - clientCache setting, like this:

<system.webServer>
 <staticContent>
  <clientCache cacheControlMaxAge="7.00:00:00" cacheControlMode="UseMaxAge" />
 </staticContent>

This will set it to 7 days

answered Feb 26, 2020 at 11:13

Robert Benyi

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