Is there a .NET API available to get data from your XBox Live account? All I'm really interested in is who's online, but messages would be cool too. And some sort of event driven notifications of user sign-on would be great, but I'll poll if need be.
Check out the Xbox Community Developer Program.
You can also try and take a look at https://xboxapi.com/ They provide a API system to get all sorts of info. Example dev: https://xboxapi.com/dev/profile/Major+Nelson
their documentation is here, https://xboxapi.com/documentation it provides info to get data in PHP json, xml, or dev.
Sadly I dont think anything like Messages and some notifications, only publicly visible info. But if you track profile info one can generate a history and if you poll the online status, you can make a popup or something
来源：https://stackoverflow.com/questions/2564692/net-xbox-live-account-api