Thanks for ur reply Lukas Pokorny..
The problem with my code was, I missed to set the HostKeyAlgorithms property before opening the connection..
I am getting the right keys after writing the below code:
sshSession.Parameters.HostKeyAlgorithms = SshHostKeyAlgorithm.RSA;
sshSession.Connect(new IPEndPoint(Dns.GetHostAddresses(hostname), sshPort));
My SshSession code was working fine without setting HostKeyAlgorithms, but the only problem was that, I was not getting the unique fingerprint...
Please let me know if there is any side effect of assigning the HostKeyAlgorithms of SshSession???