Using values from two tables to create a calculated DAX column with Switch()/IN() statement

Hi Mariusz 

Thank you for taking the time to respond. I am surprised how simple the M code is to do this! I did run into one issue though. When I attempt to duplicate this code in my own pbix project, my expanded custom column gives me null values. Due to the sensitive nature of the actual information I am working with, I cannot post my pbix file, but I can at least give the structure of the two real tables with their actual column names and some dummy data. All columns are text columns.

AD Complete

CLC_CSI

let
  (ommitted for brevity)
  #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each 
        Table.SelectRows( 
            CLC_CSI, (b) => Text.Contains( [CN], b[CLC] ) 
        )
    ),
  #"Expanded Custom" = Table.ExpandTableColumn(#"Added Custom", "Custom", {"CSI"}, {"CSI"})
in
    #"Expanded Custom"

I don't get any errors, but every value is null.