I heard of SignalR library which provide duplex communication in .NET . I want to develop some game (in web browser), let's say 2 users move their points on canvas in real time. Both players need to have refreshed canvas as fast as possible. Would signalR handle it?
I read few topics on the internet where people hate it because of low performance. I'd like try it if it would handle it.
If you have to stay with .net Stack, then SignalR would be one of your main choices and if you want to make it faster use OWIN self-host app rather than ordinary web app which needs to be hosted on IIS. So, you can remove tons of overheads. Here you can find a tutorial on how to implement self-host SignalR:
http://www.asp.net/signalr/overview/deployment/tutorial-signalr-self-host
Otherwise, if you can choose you're tech stack I'd suggest using SocketIO which is faster (in most of the senarios) and is a full-stack (NodeJs and Browser) javascript library.
Here you can find a comparison between these 2 techs :
http://stevendavistechnotes.blogspot.com.au/2016/05/comparison-signalr-vs-socketio.html