Error ‘An item with the same key has already been added’

As you already know Microsoft releases a Cumulative update every month. This update not only includes application fixes but also new client and server components. Recently I ran into a problem after copying the dll’s of the RTC and Service manually. When I restarted the service and try to connect I got stuck.

Instead of opening the client, I got the not very much saying error “The server ‘DynamicsNAV80’ was unable to process the request. The application will close”.

So, my reflex was to go to the server and check the Event Log.
There I found an even more none saying error “An item with the same key has already been added”.


After searching in SQL and trying multiple things I saw that the error was right in front of me all the time. I only need to investigate the StackTrace in detail to see that the problem must be related to the Language modules.


Then I went to the installation folder of my service and checked the language folders one by one.
First I deleted all the installed languages and restarted my service tier and try to reconnect.
And yes the client opens but only in English off course.

But what was the problem with the other language folders.
I undid the deletion and investigated the files in detail.


 And yes I found the problem. When I applied the cumulative update I forgot to copy the language dll’s. They have a version too as you can see.

After experiencing this, I’ve learned my lesson and strongly recommend everybody to automate these update actions and maybe you can take a look at the PowerShell scripts of Waldo at GitHub.

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