ASP.NET has gone fully open source. The new ASP.NET is version 5.0 (and is called vNext), is very powerful and all-encompassing.
Some of the highlights are:
1. Built in DI (dependency injection)
2. MVC 6 is built in
3. Dynamic compilation – so you change the C# code and refresh your browser and it will reflect the changes.
4. Configurable HTTP stack so sites are faster.
5. Integrated SignalR 3.0
View the introduction at: https://weblogs.asp.net/scottgu/introducing-asp-net-5
For in-depth understanding: https://msdn.microsoft.com/en-us/magazine/dn913182.aspx