> (I don't understand what you mean by "it won't compile", because it will, in most cases System.Linq namespace is already referenced anyway, either through glo

> (I don't understand what you mean by "it won't compile", because it will, in most cases System.Linq namespace is already referenced anyway, either through global usings or at the top of the file) The "in most cases" is doing all the lifting here. Rust's Iterator is in the prelude. Even if you #![no_std] you get the core prelude which has core::iter::Iterator. You would need to explicitly write code to tell Rust "No, I don't want the prelude" to get rid of it, I'm sure people do that, otherwise it wouldn't be possible, but few enough that I've never seen it. But in C# there is no such promise. In most (but not all) real world C# projects somebody already brought in LINQ. If you're using a technology that gives you a "ready to go" standard C# project template it undoubtedly folds in LINQ too. But it's not actually provided by the language and that's a meaningful gap. Notably in several of the playground type tools, since LINQ is not there by default this won't work - like I said it won't compile and it doesn't suggest "Oh you need LINQ" because the C# compiler doesn't provide such suggestions.