Mads Kristensen

My personal blog about everything tech

I’ve been working lately with some ASP.NET performance optimization automation HTTP modules. In one of them I needed to know if the last-modified header had been set through the Response.Cache.SetLastModified(DateTime) method. For some reason, there is no API available anywhere within the BCL to retrieve the last modified date of a response – you can only set it.

Since the module wouldn’t work without a way to read the last modified date of the response, I had to use Reflector to figure out how to pull the information out using reflection. The result became a simple little method to retrieve the date. It looks like this:

private static DateTime ReadLastModifiedFromResponse(HttpCachePolicy cache)

{

  BindingFlags flags = BindingFlags.NonPublic | BindingFlags.GetField | BindingFlags.Instance;

  return (DateTime)cache.GetType().GetField("_utcLastModified", flags).GetValue(cache);

}

And you can use it like this:

DateTime responseModified = ReadLastModifiedFromResponse(Response.Cache);

 

if (responseModified > DateTime.MinValue)

{

  // Last-modified is set. Do something...

}

If you know of another way to retrieving the last-modified date, please let me know.

When I was building the mobile TV guide I found that there are a couple of things needed to make the website look better on the iPhone and iPod. They both have some extra capabilities that is easy to utilize when you know how.

Zoom level

The first is the zoom level. By adding the meta-tag below, you can specify the viewport to fit perfectly with the iPhone/iPod. The meta-tag tells the Safari browser to zoom in to a specific level as specified. It was a trial and error process of finding the correct zoom level, but very easy as well.

<meta name="viewport" content="width=280, user-scalable=yes" />

Bookmark icon

Another tag tells Safari that when a website is bookmarked, it should use a specific icon to put on the dashboard of the iPhone or iPod. For some reason Apple invented a new link-tag for this instead of just supporting the favicon standard. The link-tag looks like this:

<link rel="apple-touch-icon" href="favicon.ico" />

Programmatically

Since the TV guide is made especially for mobile phones, it was important to keep the download size of the page as small as possible. That’s why I choose not to add these two tags by default, but only when the browser visiting the site was either an iPhone or iPod.

To do that programmatically, I simple added this method to my master page:

private void AddIPhoneHeaderTags()

{

  string ua = Request.UserAgent;

  if (ua != null && (ua.Contains("iPhone") || ua.Contains("iPod")))

  {

    HtmlMeta meta = new HtmlMeta();

    meta.Name = "viewport";

    meta.Content = "width=280, user-scalable=yes";

    Page.Header.Controls.Add(meta);

 

    HtmlLink link = new HtmlLink();

    link.Attributes["rel"] = "apple-touch-icon";

    link.Href = "favicon.ico";

    Page.Header.Controls.Add(link);

  }

}


Of course, these two tags will work for all websites – not just the ones made especially for mobile phones.