Wcf - using duplex - callbacks

Question

I'm creating a wcf project with a wpf client using mvvm design pattern, Where do I need to implement the ICallback interface so I will be able to update the window.

Answer 1

The callback contract should be implemented on the client-side. Likewise, the service contract should be implemented on the server-side, with which the server can send data to the client-side by the callback contract.
Please refer to my example of the previous post.
TimeOut exception in WCF while implementing duplex
the client sends a parameter to the server by using the service interface, subsequently, the server sends the handled result to the client with the callback contract so that the client application gets the updated.
Feel free to let me know if there is anything I can help with.