new to ssh,I can not get a command from 'crm_mon'

[chiglish]

i would like to access remote HA server cluster ,use 'crm_mon' to check server status,i can not get a result from sshcommand.result
also I tried params like 'crm_mon -1','crm_mon --as-xml',neither could get result

using (var client = new SshClient(my servers info) { client.Connect(); using SshCommand cmd = client.RunCommand("crm_mon'"); Console.WriteLine(cmd.Result); // no result return }

but when I excute 'df -h' or 'free -h', I can get a result.

could anyone help?Thanks.