Check if all values exist

Hi jacccodezwart 

Here's one way to do it.  This is a measure that will give you True or False for each OrderKey.

I've assumed your model is 2 disconnected tables

Has All Activity Codes = 
VAR _Orders = 
SELECTCOLUMNS(orderlines, 
    "ContractNumber", orderlines[OrderContractNumber] & "",
    "ActivityKey", orderlines[ActivityKey] & ""
)
VAR _Contracts = 
SELECTCOLUMNS(contractlines, 
    "ContractNumber", contractlines[ContractNumber] & "",
    "ActivityKey", contractlines[ActivityKey] & ""
)
VAR _Joined = 
NATURALINNERJOIN(_Contracts, _Orders)
VAR _ContractActivityCount = 
CALCULATE(
    COUNTROWS(contractlines),
    contractlines[ContractNumber] = SELECTEDVALUE(orderlines[OrderContractNumber])
)
RETURN
    _ContractActivityCount <= COUNTROWS(_Joined)

The '& ""' are there to break lineage, so NATURALINNERJOIN will combine _Orders and _Contracts