Dictionary cache regression

JamieT · October 1, 2025, 12:35pm

Thanks, issue in progress.

Looks like Callum did this feature in

github.com/umbraco/Umbraco-CMS

Cache null dictionary values by key

v13/dev ← callumbwhyte:15533-dictionary-cache

opened 10:12AM - 15 Jan 24 UTC

callumbwhyte

+45 -11

As discussed on #15533 a small performance issue can exist at scale whereby each… subsequent call to `Umbraco.GetDictionaryValue("...")` for non-existent keys results in a database lookup. This PR implements an option to cache null values in the repository layer, and enables for the `DictionaryByKeyRepository` repository, following @Migaroez's stellar recommended implementation [here](https://github.com/umbraco/Umbraco-CMS/issues/15533#issuecomment-1885007320).

and then regressed here

github.com/umbraco/Umbraco-CMS

fix: check for NullRepresentationInCache in AppCacheExtensions

main ← crjc:fix/app-cache-ex

opened 11:59AM - 17 May 25 UTC

crjc

+15 -9

### Description I have noticed the back-office being noticeably slow during d…evelopment of some websites (V13). The console output is **flooded** with the following while navigating the CMS: ``` Exception thrown: 'System.InvalidCastException' in System.Private.CoreLib.dll Exception thrown: 'System.InvalidCastException' in Umbraco.Core.dll Exception thrown: 'System.InvalidCastException' in System.Private.CoreLib.dll Exception thrown: 'System.InvalidCastException' in Umbraco.Core.dll ...(thousands of times)... ``` This PR updates `GetCacheItem` to check for `NullRepresentationInCache`. This prevents the above flood of exception handling and also improves performance. Umbraco was seemingly trying to cast the string `"*NULL*"` to `IDictionaryItem` thousands of times while doing basic operations such as opening a page in the CMS. I moved `NullRepresentationInCache` to AppCacheExtensions.cs in this PR. I understand this may not be the best place for this constant.