how to use controller and contract class in query based report

hi all,   

  i have created a Query based report , for this report, I need to pass the parameter enum type for that i had created contract class (note : That enum field doesn,t exist in dataset and table) and controller class , in controller class calling this contract class after i am trying to open the report this error comes "The value "EAMGraphGlobalContract" is not found in the map"

Actual scenario is I am passing parameter enum is currentyear/previous year , in my dataset having the field year if  I select currentyear it takes current year value and if i select previous year it taken as currentyear-1 . based on that selection enum  I want to filter the year wise data

Thanks

veer