I figured out the problem causing for the issue. It is due to the misconfigured runspace i created.
InitialSessionState initalState = InitialSessionState.Create();
initalState.ImportPSModule(new String[] { "msonline" });
//initalState.LanguageMode = PSLanguageMode.FullLanguage;
Office365Runspace = RunspaceFactory.CreateRunspace(initalState);
Office365Runspace.Open();
i was creating the initalstate with empty one,When i changed it to default one it worked fine.On creating the default one it includes all the modules that were obtained by default.
InitialSessionState initalState = InitialSessionState.CreateDefault();
it worked fine.
Thanks, Satya