I just published a code sample to demonstrate the most basic way to enable file uploading in ASP.NET MVC 5. It supports both single file uploading and multiple file uploading. The code sample does not use any 3rd party/jQuery controls.
Code Sample Download: http://scottge.net/product/asp-net-mvc5-sample-file-upload/ (The code sample has high quality, and I maintain it constantly. Please feel free to leave your technical questions in the sample download page. I will help you.)
After you download the sample, you will get the complete source code to debug and run. The code sample can be easily extended to support more advanced functions