For now i create topic using
in thats require one token
right now i create thats token at android and ios.
Now as i need to create Topic with rest call at server side in c#
so anythings in that i am able to create that token at c# side and create TOPIC at server side ?
You can't create token on server side. Your application should register the device it is running on Google Cloud Messaging. Then your application generates the token and sends it to your server which can then use it.
See the Instance ID lifecycle documented here https://developers.google.com/instance-id/#instance_id_lifecycle
You can check this sample here: http://avilyne.com/?p=267 The client and server code are written in Java but it should be easy to convert it in its C# equivalent.