The error is:
I appreciate the helpful "(are you missing a using directive or an assembly reference?)" but I don't know what that means. It could be for the programmer.Generated code at (1245, 31) 'voter' does not contain a definition for 'one_ODCV' and no accessible extension method 'one_ODCV' accepting a first argument of type 'voter' could be found (are you missing a using directive or an assembly reference?) (context: executing StoreVariablesyAndResetBuffers(); aggregate "Sum one", in collec-tion_of_voter_by_politician_supported)
Here's when the error occurred, so that you might be able to replicate the error. I created a collection of Voter partitioned on politician supported. Now I need the count of voters for each politician. On the Voter[politician supported] diagram, I dragged and dropped an aggregate, and then edited it. I changed Aggregation Function to Sum and Target Variable to one. The one auxiliary equals 1. I did this because there is no Aggregation Function for Count. Then I ran the model and the error occurred.
Testing, I see that if I change Aggregation Function to None there is no error, only a warning: 'Aggregate "Aggregate1" Chosen aggregate function is "None"; the value will always be 0.' Thus the error is provoked by setting Aggregation Function to Sum.
Is there perhaps a better way to count the entities in each partition in a partitioned collection?
Thanks. This is a showstopper, though I've not yet explored how I can get past it.