That's part of .NET Framework and therefore legacy, right? Do the database libraries from recent versions of .NET do this?

In any case, it's just one framework; previous comment said "all major languages". And it's useful to be able to abstract and compose over expressions and predicates and such, not just data values, which this still doesn't help with.

> That's part of .NET Framework and therefore legacy, right? Do the database libraries from recent versions of .NET do this?

ADO.NET is available both in the legacy Windows-only .NET Framework and in the new cross-platform .NET (previously known as .NET Core).

> In any case, it's just one framework; previous comment said "all major languages".

Well, you are not implementing a piece of code in "all major languages" - you can pick the one that fits the problem best.

> And it's useful to be able to abstract and compose over expressions and predicates and such, not just data values, which this still doesn't help with.

You can do that via LINQ - there is even special query-like syntax built right into C# for that that looks like this:

    var companyNameQuery =
        from cust in nw.Customers
        where cust.City == "London"
        select cust.CompanyName;

But anything non-trivial is much better done in SQL proper, IMO. Most of the time, at least for OLTP, you'll be using static SQL - that is you will not need to change the text of the SQL query, just parameters. But dynamic SQL is a thing and can be very useful on occasion - which is string concatenation with all the problems that might bring.