https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.keynotfoundexception?view=netframework-4.8.1&redirectedfrom=MSDN
KeyNotFoundException Class (System.Collections.Generic) | Microsoft Learn
The exception that is thrown when the key specified for accessing an element in a collection does not match any key in the collection.
class systemcollectionsgenericmicrosoftlearn