Consolidate "C# concepts" and "C# programming guide"

There are two sections of the C# documentation which seem to fill overlapping if not identical areas, under [Docs](https://docs.microsoft.com/en-us/) -> [.NET](https://docs.microsoft.com/en-us/dotnet/) -> [C# guide](https://docs.microsoft.com/en-us/dotnet/csharp/):

* C# concepts (for example, [this page](https://docs.microsoft.com/en-us/dotnet/csharp/nullable-references))
* [C# Programming guide](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/)

For example, both have sections on LINQ ([here](https://docs.microsoft.com/en-us/dotnet/csharp/linq/) and [here](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/linq/)) and expression trees ([here](https://docs.microsoft.com/en-us/dotnet/csharp/expression-trees) and [here](https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/expression-trees/)).

Which hierarchy should be preferred?

Would it be useful to draw up a table of the duplicate sections?