MVVM Light is a popular, 3rd party framework based on the Model-View-ViewModel pattern by Laurent Bugnion. The MVVM Light Toolkit helps you to separate your View from your Model which creates applications that are cleaner and easier to maintain and extend. It also creates testable applications and allows you to have a much thinner user interface layer (which is more difficult to test automatically).
This toolkit puts a special emphasis on the "blend ability" of the created application (i.e. the ability to open and edit the user interface into Blend), including the creation of design-time data to enable the Blend users to "see something" when they work with data controls.
You can find more out at MVVM Light's homepage
MVVM Light also provide an extension for Visual Studio 2017 that includes templates, snippets, and other resources you may find helpful.