How to query many-to-many releationship in EF Core

You'll need to manually do this since EF Core won't load associated properties automatically, but something like the following should work:

var result = context.Begrip
    .Include(x => x.Categories)
    .ThenInclude(x => x.category);

Note that Intellisense may not always function on.ThenInclude at the present, but even if it receives a red underlining, the code should still compile.

You should probably map this to a DTO if you're returning this to the view or an API so you don't have to worry about.Categories[0].category.Name etc.