How to assign null or blank value to an extended data type/Enum type field in X++

In a SSRS report DP class, I have a in memory table called bookingsTmp. I want some fields be blank in my report.  So I hard coded them as following: 

bookingsTmp.ProjectStage = ""; -----Data type of ProjectStage is EnumTypeProjStatus

bookingsTmp.FiscalYear = ""; -----Data type of FiscalYear is ExtendedDataType Year

bookingsTmp.ProjectBookedDate= ""; ---Data type of ProjectBookedDate is ExtendedDataType TransDate

I got error message "Operand types are not compatible with the operator". if I change 

bookingsTmp.ProjectStage =0; 

bookingsTmp.FiscalYear = 0; 

No compiler error. But there are values in my report. 

For the Date field ---bookingsTmp.ProjectBookedDate , I tried assign it 1900-01-01 , still get error. I also tried convert it to string, no luck. 

Basically, I  don't want to display any values in my report for those 3 fields. How to do it?