I started working on something very similar for .NET and EntityFramework 7 based on some other ideas I've implemented over the years.

https://github.com/lukemurray/EntityQueryLanguage

Super early days as I haven't had too much time on it, and now GraphQL has specs etc. I might support more of it's syntax.

I actually build .NET expression so you can execute things against any LINQ provider - in-memory, Entity Framework, or some other ORM