[kreutzwj]

> they made it possible to provide your own implementation of all the query operators so it was possible for me to define my own methods and make my linq queries not allocate at runtime. really nice (though it comes with its own tradeoffs).

I would like to know more about this, would be really useful. So you have any recommended docs to read?

[kevingadd]

I don't have a bookmarked page about this, but essentially if you implement your own version of the extension methods from the Linq namespace, the compiler will prefer those over the IEnumerable<T> extension methods. If you want to debug this a great way to do it is to examine the generated binary in a decompiler and you should see which methods the compiler decided to use. The async/await support also works this way - it will just look for methods with an appropriate signature and try to use them if possible: https://devblogs.microsoft.com/pfxteam/await-anything/

For both of the above examples, it's sufficient to write extension methods that target a specific type, so you don't have to change the actual types you want to query or await - just provide extension methods. This means you can do it for types you didn't write, as well.

For more advanced scenarios, you can write a query provider that consumes expression trees, and the compiler will generate an expression tree for your library to consume instead of calling a bunch of methods: https://docs.microsoft.com/en-us/archive/blogs/mattwar/linq-...