LINQ is on the right track but doesn't quite go far enough with query composition. For instance, you can't "unquote" a query within another query (although I believe there is a library that tries to add this).

EF code-first is also on the right track, but the fluent and attribute mapping are awkward, foreign key associations often have to be unpacked directly as value type keys, there's no smooth transition between in-memory native types and durable types, and schema migration could be smoother.

Lots of the bits and pieces of what I'm describing are around but they aren't holistically combined.

Can you elaborate on what you mean by "unquote"? I've not heard this term and I can't find any relevant info from search.

In F# and MetaOCaml it's called splicing:

https://learn.microsoft.com/en-us/dotnet/fsharp/language-ref...