HelpSteam API for C#?

Hello,
I've been looking for a long time on the web for a Steam API or any other thing that would allow my C# application to keep connect a steam account. And if possible, an API that allows user to buy stuff on steam with steam wallet (I doubt it exists but it worths nothing to ask, huh?).

Thanks!

Some API wrapper links:
https://developer.valvesoftware.com/wiki/Steam_Web_API
https://github.com/Overv/SteamWebAPI
NuGet Gallery | Fluent Steam Web API for C# 1.0.9

As for accessing the Steam Wallet don't think you can from the web API. You can try using the open-steamworks, but I'm not sure it still works anymore:
VoiDeD / Open Steamworks — Bitbucket