To handle the concurrency in ASP.NET application, the Entity Framework 6 Code First and Visual Studio is a good option. What say?
Concurrency is a remarkably vague term when it comes to web development; in what sense are you referring to? Though given what a train wreck ASP.NET vomits up for website if you rely on junk like Visual Studio, I'd have to do a Nancy Reagan impersonation; Just say no. You want to build a native application, Visual Studio is fine... you want to build a website that people will visit, you're shooting the horse in the foot before the gate even opens. Though really that depends a LOT on what it is you want to make go on simultaneously... which you didn't say.