.NET 4.5 WebSockets vs SignalR

I think SignalR is the way to go, and is going to be part of .NET itself anyway (and likely extend/merge/replace web-sockets support). It uses web sockets when it's supported, and consistent client polling hack when it's not, so, it's the way to go.

Update:

Since this answer is still getting upvoted, it's worth mentioning that SignalR is now officially part of ASP.NET.

Check http://asp.net/signalr

Update: .NET Core

SignalR is also being added to .NET Core as @yazanpro noted in comments.

It's available in .NET Core 2.1, and has official documentation as well.

1. I'm wondering if the WebSocket feature does actually do the same as SignalR and fall back to long polling when WebSockets aren't available?

   WebSockets is a new protocol independent of other communication techniques. From the RFC

   The goal of this technology is to provide a mechanism for browser-based applications that need two-way communication with servers that does not rely on opening multiple HTTP connections (e.g., using XMLHttpRequest or s and long polling).

2. Surely Microsoft would implement the same technology as SignalR in their approach to this technology?

   Not if they want to conform to the specification they won't. There's certainly nothing stopping Microsoft from developing a higher level API similar to SignalR that would abstract away communication detail and offer graceful fallback. However that hypothetical API would probably build on top of WebSocket class as opposed to replacing it.

SignalR uses OWIN which will use WebSockets connection if the browser supports web sockets and long polling if the browser doesn't support WebSockets.