Try our conversational search powered by Generative AI!

Stephan Lonntorp
Nov 18, 2016
(2 votes)

Ensuring image extension for content URLs

When using an image resizing component, like we do in the Focal Point plugin, it's really important that the file extension is there. If it's not, the resizing engine won't kick in for the request, and that enormous image is sent straight to your mobile users, and they will forever hate your guts.

I've implemented a solution using the new (in CMS 10) IUrlSegmentCreator events, and a regular InitializationModule. Code below. It uses the first registered extension for your media type as the default extension for the URL segment. This works for me, since I have separate Media types for all image files, like JpegImage, PngImage etc, to be able to more granularly control their usage, through the AllowedTypes attribute. If you have a single MediaData for all your images, I recommend altering the extension mapping to maybe use the MimeType property and get an appropriate extension based on that. 

/*using System;
using System.IO;
using System.Linq;

using EPiServer;
using EPiServer.Core;
using EPiServer.Framework;
using EPiServer.Framework.DataAnnotations;
using EPiServer.Framework.Initialization;
using EPiServer.Web;

[InitializableModule, ModuleDependency(typeof(EPiServer.Web.InitializationModule))]
	public class ImageDataInitialization : IInitializableModule {
		private bool eventsAttached;
		public void Initialize(InitializationEngine context) {
			if(!this.eventsAttached) {
				var creator = context.Locate.Advanced.GetInstance<IUrlSegmentCreator>();
				creator.Created += CreatedMediaSegment;
				this.eventsAttached = true;
		private static void CreatedMediaSegment(object sender, UrlSegmentEventArgs e) {
			var content = e.Content as ImageData;
			if(content != null) {
				var extension = Path.GetExtension(content.RouteSegment);
				if(string.IsNullOrWhiteSpace(extension)) {
					var type = content.GetOriginalType();
					var fileExtension = GetExtensionForType(type);
					if(!string.IsNullOrWhiteSpace(fileExtension)) {
						content.RouteSegment = content.RouteSegment + "." + fileExtension;
		private static string GetExtensionForType(Type contentType) {
			var mediaDescriptorAttribute = contentType?.GetCustomAttributes(typeof(MediaDescriptorAttribute), false).OfType<MediaDescriptorAttribute>().FirstOrDefault();
			return mediaDescriptorAttribute?.Extensions?.FirstOrDefault();
		public void Uninitialize(InitializationEngine context) {
			var creator = context.Locate.Advanced.GetInstance<IUrlSegmentCreator>();
			creator.Created -= CreatedMediaSegment;
			this.eventsAttached = false;
Nov 18, 2016


valdis Nov 22, 2016 09:55 PM

I'm not fan of hacks, but theoretically if you happen to have project with extension less images (which is weird) in it, you can tell IR to kick-in. See Nathanael answer.

Stephan Lonntorp
Stephan Lonntorp Nov 22, 2016 10:27 PM

Thanks, but that seems like a can of worms. I cannot know all paths that csn, or cannot, contain an image. I think I'll stick with this approach. :)

Please login to comment.
Latest blogs
Join the Content Recommendations Work Smarter webinar May 8th 16.00-16.45 CET with expert Aidan Swain

Learn more about Content Recommendations, with Optimizely’s very own Senior Solutions consultant, Aidan Swain . He will discuss best practices and...

Karen McDougall | Apr 12, 2024

Plugin for Identifying and Bulk Deleting Orphaned Missing Properties in Optimizely

I am aware that the Optimizely World community has extensively discussed this topic, with numerous solutions and code snippets available to help...

Adnan Zameer | Apr 11, 2024 | Syndicated blog

Enhancing the Authoring Experience: Extending the LinkItem

The LinkItem field is one of the most demanded properties by the community, allowing editors to effortlessly create and manage links across pages a...

Santiago Morla | Apr 10, 2024 | Syndicated blog

The distinctions between Optimizely Web Experimentation and Optimizely Feature Experimentation

This blog is part of the series - Unlocking the Power of Experimentation: A Marketer's Insight. Let’s dive into Optimizely's powerful experimentati...

Holly Quilter | Apr 9, 2024