Web api :format api/controller?parameter= not working

Question

Hi friends

 

when I am trying with this format api not working.

 

Web Api development(.net core 2.MVC)

 

api/controller?parameter= 

 

where as when I am giving / in place of question mark it is giving the json result.

 

api/controller/parameter= 

 

please help me to fix the above issue.

 

Thanks in advance.