Android Studio is best tool for android development.
It includes Android 5.0 (Lollipop) Platform
Android 5.0 emulator system image with Google APIs (New features).
You can download it from the below link:
DNS Gold Member
"Failure is the path of least persistence"
If you are comfortable with .net then go for software called "XAMRIN".
In this we can code using c#.
Hope this helps!
However, if you are set on using .NET, Sunil suggestion is a good one and you can also use mono sdk with it.
Here is a useful link that you can take a look at: