How can I use Bootstrap Sass at Visual Studio?
There're many way to achieve this, but you can just use Nuget with visual studio to do this.
Nuget + Web Compiler
Use nuget to download the sass bootstrap to your web application.
PM> Install-Package Twitter.Bootstrap.Sass
Once you have installed bootstrap file to your application, you can install following visual studio plugin to compile the sass to css.
This web compiler will compile the sass into css file for you.