POSTMAN requests work but C# request does not work

I want to set text range. Mastership request is require. Firstly request mastership in POSTMAN. Use this call curl --digest -u "Default User":robotics -X POST "http://localhost/rw/mastership?action=request" after that I try set text range with this curl --digest -u "Default User":robotics -d "task=T_ROB1&replace-mode=After&query-mode=Force&startrow=4&startcol=8&endrow=4&endcol=15&text=SampleTest" -X POST "http://localhost/rw/rapid/modules/Hareket_Noktalari?action=set-text-range" in POSTMAN. Working without error. When I want to same thing in C#, I use POSTMAN Code Snippet C# codes. I get this error "User does not have required mastership". Please help me this situation.