Calculation expression evaluation error

If the custom function ID (guid) specified in the class for the assembly does not match with the ID of the custom function specified in the extensions.json file, the user is presented with the following error message:

Calculation expression evaluation error.. Stack Trace: System.Exception: Calculation expression evaluation error. ---> Intelatrac.Mobile.ProcedureController.Calculation.CalcEngineException: Invalid operator/function in the calculation expression: @CSGetCatalogCodes

at Intelatrac.Mobile.ProcedureController.Calculation.CalcBuilder.GetTokenType (System.String s) <0x6cb9da90 + 0x002ac> in <filename unknown>:0

at Intelatrac.Mobile.ProcedureController.Calculation.CalcBuilder.BuildTokens (System.Collections.Generic.List`1 arrTokens, System.Collections.Generic.List`1 arrPrefix, IDataContext dataContext, Boolean OldCalcExpression) <0x6cb9a028 + 0x00413> in <filename unknown>:0

at Intelatrac.Mobile.ProcedureController.Calculation.CalcEngine.GetRootToken (System.String calcExpression) <0x6cb99210 + 0x000e7> in <filename unknown>:0

at Intelatrac.Mobile.ProcedureController.ProcedureNodeBase.CalcValue (Intelatrac.Mobile.ProcedureController.MobileProcedure currentProcedure, Boolean updateReferenceNodes) <0x6cb54b10 + 0x00177> in <filename unknown>:0

--- End of inner exception stack trace ---

To resolve this issue, make sure the custom function ID (guid) and the ID of the custom function specified in the extensions.json file are the same.