c# - Skype4COMLIB skype.message.chat.sendmessage -

i have problem c# code trying change group chat topic not work

private void button10_click(object sender, eventargs e)     {         skype skype = new skype();         skype.message.chat.sendmessage("/topic " + textbox9.text);     } 

and when press button says unknown message

you have attach skype skype.attach(); should make 1 global skype object , on form load should attach skype.