Hello Akhil,
Great, sounds like you are using the core/command example I gave you first, where you get the output (stream) in the response.
I may have confused you by changing from the simple core/command request used in the first example to the more advanced sync/copy request.
I changed because you need to use the sync/copy command to be able to get the copy progress. It will return immediately with an OK (job started) and then you can use repeated core/stats requests to monitor the progress.
Here is a step by step guide to use sync/copy and then monitor status:
First start "rclone rcd --rc-no-auth", then initiate the copy something like this (note the URL):
it will return almost immediately and then you can monitor status with repeated calls something like this:
you can see the returned status in the middle of my above screenshot.
I think you can easily translate the above REST requests into C# by editing the example I gave for the core/command request.