Net 9.0 LINQ Performance Improvements

For me, the most useful part of LINQ is neither the IQueryable syntax tree based extension mechanism, nor the language integrated part (which I dislike), but simply the IEnumerable extensions. Originally known somewhat confusingly as linq to objects. Those allow me to write c# in functional style, keeping the code concise.

The post I submitted refers mostly to optimizations to those extension methods.

This clicked for me after having learned Haskell. It also shares some of Haskell's features/pitfalls, such as laziness.

There are pitfalls, sure, and honestly I wouldn't advise a team having no one somewhat experienced with basic functional idioms (including laziness) to use it. It can lead to obtuse and slow code if used indiscriminately. I try to lead by example myself.

Totally. I couldn't care less if the LINQ syntax had gone tomorrow, but functional composition is so powerful, and easier to maintain too.

I would miss it for `let`, and for multiple `from` clauses. These are things that can be done with extension methods and callbacks, just not as elegantly.

`let` is just a .Select(), isn't it?

A `Select` to a tuple or anonymous class which you have to carry around all the way.

If you look at how a LINQ query gets translated to a method chain (e.g. via SharpLab or let Rider/ReSharper rewrite them) you'll notice that multiple `from`s or `let`s can become quite ugly.