--- title: "Caching in WinForms" url: "https://osherove.com/blog/2003/8/12/caching-in-winforms.md" canonical: "https://osherove.com/blog/2003/8/12/caching-in-winforms.html" published: "2003-08-12T16:44:00" updated: "2003-08-12T16:44:00" tags: [".Net Original"] author: "Roy Osherove" description: "Just out of curiosity I decided to try out some caching experiments in winforms. I wasn’t out to do any performance counting or anything, but I was playing around with the caching application block. After messing with…" usage: "Licensed under CC BY 4.0 — reuse, quote and adapt with attribution (Roy Osherove, link to the original page)." license: "https://creativecommons.org/licenses/by/4.0/" --- # Caching in WinForms By Roy Osherove August 12, 2003 In [.Net Original](https://osherove.com/blog/category/net-original) **Historical article** · Originally published August 12, 2003; technical details may be outdated. Just out of curiosity I decided to try out some caching experiments in winforms.  I wasn’t out to do any performance counting or anything, but I was playing around with the caching application block. After messing with it for a while, I remembered that I had already seen a very easy implementation for caching even **before** the caching application block was released.  This caching implementation actually used the System.**Web.Caching.Cache** class (usually used in ASP.NET applications) for the caching. So, I decided to try it out. It turned out to be one of the simplest things ever. Simple steps to using the ASP.NET cache in a non-web application: - Add System.Web to your references - Get the actual cache object using private Cache m\_Cache; m\_Cache = HttpRuntime.Cache; - Now you can use all those wonderful cache features such as expirations and file dependencies in your application. One more thing: \-         You do **not** need IIS installed on the machine in order to work with the Cache object Now, here’s something funny I discovered when using the Cache object; one of the coolest features that it exposes it “sliding expiration time” and “absolute expiration time” for stuff you put in there. Basically this means that I can put my stuff in the cache, and make that stuff “expire” say, 20 minutes from now(sliding expiration). Not only that. I provide a callback function that will be called when that item actually expires so I can re-fill the cached item and thus “refresh” it.  If we’re dealing with absolute expiration time, it will only be called on a specific date and time provided by me. For example  “expire this item on 12/12/03 00:00”. Very cool. BUT – here’s a little snag I fell into: I added an item to the cache like so: m\_Cache.Add("ds",ds, null,DateTime.MaxValue,TimeSpan.FromSeconds(3),CacheItemPriority.High,new CacheItemRemovedCallback(OnItemRemove)); without getting into too much detail – I’m adding an item that will expire 3 seconds from now (sliding expiration) and want my callback function to be call when it expires. On my callback function I re-add the expired item in the same way – to expire in 3 seconds. And so on. I have a form and a button that when clicked tries to get the value of  the cached item. I put a Debug message in my callback function to know when I have an expired item. Now I run the application. I don’t click anything for 10 seconds. Then I click the button. What do you think happened? **The callback was not called until I clicked the button** Yep – that’s right. I get the callback only the first time my code tries to access the item after it has already expired. Can you see why this might be a bad thing? Suppose I have some very complicated data cached in there. And suppose it takes me 30 seconds to refresh that data.  Instead of this data being refreshed an given intervals, I am faced with the fact that the next used that tries to access this data will have to wait 30 seconds for it. This fact is also stated in [this MSDN article](http://msdn.microsoft.com/asp.net/default.aspx?pull=/library/en-us/dnaspp/html/aspnet-cachingtechniquesbestpract.asp#aspnet-cachingtechniquesbestpract_topic4). I wish I had a more deterministic way of using this event.  Anyway – some pointers about using this **Web.Caching.Cache** (some may not agree, but there are my views): \-         If you need caching within your appdomain, and not shared in other places – this is the fastest and easiest way to go. \-         For more complicated stuff (like sharing on a larger scope, deterministic expiry times and the ability to provide your own dependency resources) look to the [Caching application block](http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnpag/html/CachingBlock.asp) ## More in .Net Original [All posts in .Net Original](https://osherove.com/blog/category/net-original) - Aug 12, 2003 ### [Catch ex As Exception When...](https://osherove.com/blog/2003/8/12/catch-ex-as-exception-when.html) - Aug 12, 2003 ### [My new favorite book](https://osherove.com/blog/2003/8/12/my-new-favorite-book.html) - Aug 11, 2003 ### [Server.Transfer vs. Response.Redirect](https://osherove.com/blog/2003/8/11/servertransfer-vs-responseredirect.html) - Jul 28, 2003 ### [About coding standards](https://osherove.com/blog/2003/7/28/about-coding-standards.html) --- ## About the author **Roy Osherove**: Senior Solutions Architect at AWS working on AI for production and AI-driven development; author of The Art of Unit Testing and Elastic Leadership, with about 20 years of consulting and training on unit testing, TDD, team leadership and continuous delivery. ### Sites - [RobotPaper](https://robotpaper.ai/): This blog: AI patterns and anti-patterns, AI and coding agents, and engineering leadership. - [osherove.com](https://osherove.com): Roy's personal site. Author of The Art of Unit Testing and Elastic Leadership; consulting and training on unit testing, TDD, team leadership and continuous delivery, plus about 20 years of blog posts. - [The Art of Unit Testing](https://www.artofunittesting.com): The Art of Unit Testing, 3rd Edition (Manning): readable, maintainable, trustworthy unit tests, plus TDD workshops in C#, JavaScript, Java and Kotlin. - [5whys.com](https://www.5whys.com): Roy's writing on software team leadership: self-organizing teams, surviving chaos, learning mode and the Elastic Leadership model. - [Pipeline Driven](https://pipelinedriven.org): Continuous delivery and DevOps practices: build patterns, pipeline-friendly testing, DevOps metrics and enterprise DevOps. - [Elastic Leadership](https://www.elasticleadership.com): Elastic Leadership, Roy's framework for software team leaders (survival, learning and self-organizing modes). ### Social - X: https://x.com/royosherove - LinkedIn: https://www.linkedin.com/in/osherove/ ### Contact - Contact form: https://forms.gle/jQSx5KoXvrVA1JCK7 ### License Licensed under CC BY 4.0 — reuse, quote and adapt with attribution (Roy Osherove, link to the original page). License: https://creativecommons.org/licenses/by/4.0/