Microsoft has a series of tutorials using Unity for Hololens. Udacity just launched a new VR course using Unity as well.

However, performance can be a critical factor depending on the app, and C++ may be the only solution. For that you need low-level knowledge of shader+texture+render techniques, which for Hololens is generally all in DirectX.

There are very few business-oriented frameworks for any of the devices, almost everything is designed for gaming (short scripts and machine-oriented code organization). Implementing most of what we normally imagine being part of an 'app' has to be done from scratch.

Source: I am doing a Hololens startup.

Get Unity or Unreal. Unity uses C#, Unreal uses C++ or a visual scripting system called Blueprints.