- While we're in here looking at caching rules for our CDN cache, let's take a look at a custom caching rule. What we're going to do in this demonstration is define a custom caching rule that invalidates our CDN cache after a specified amount of time. What we're going to do in this demonstration is use a custom caching rule to set a cache duration of one second on our cdndemo.htm file. What this will do is override any cache control or expires http headers that are sent by the originating server. 

So to create our custom caching rule, we'll browse down here, down to the custom caching rule section. So to define our custom caching rule, we'll go down to the bottom here where it says custom caching rules. So to create our custom caching rule, what we're going to do is go down to the bottom here where it says custom caching rules. What we're going to do for the match condition field is set it to path. The value we're going to match on is our cdndemo.htm file. The caching behavior we're going to set is override and we're going to tell it that we want a cache duration of one second. We can go ahead and save our new rule. 

With our new rule in place, what we'll do is go up to our web app and we'll refresh it. And we can see we have black text. If we switch over to our end point, we can refresh and we see we have black text. Now what I'm going to do is go into my FTP client again and I'm going to edit the text color back to red. Now if I go back up to my application and refresh, we can see I get red text. Now what I would expect in my end point is that a refresh also displays red text. This is because the custom rule down here should override the default cache expiration of seven days because I'm focused on the cdndemo.htm match. So let's go up here and do a refresh and as you can see here, the text is in fact red. So what this demonstrates is that I can control individual caching with custom caching rules. Our custom rule here that matches on the cdndemo.htm file overrides the default caching expiration duration of seven days. And if you read closely under the custom caching rule section, Microsoft will tell you that these rules override the default settings above and that they're evaluated from top to bottom. That being said, rules that are lower in this list can override rules that are further above it. So keep that in mind when you start creating custom caching rules.