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Comment by kaidon | Hacker News Reader

Type inference with `var` as well; which was necessary for LINQ anyway IIRC.

Why is it useful for LINQ? I feel like it’s mostly dependent on lambdas and generics.

There are anonymous types for intermediate results in the linq stream. And since they are anonymous types you need the c var keyword when working with the outcome.

….All these years and I’ve never known about Anonymous types. I know about records and dynamic objects. I’m guessing they aren’t used often because I have yet to find them.

LINQ GroupBy() is the most common use I can think of. I would definitely look into that as it's a nice tool to have. Otherwise, keep them in mind if you're ever pulling data from an external source (SQL, JSON, GQL, Redis, etc) and you're annoyed about having to make a class for some trivial operation.

If a library doesn't have an API for using them with generics, you can paper over that with:

    T fn<T>(T throwAway) => Library.Deserialize<T>();

Another example of Anonymous types would be a simple .Select(x=> new {x.ID, x.Name});

Sometimes people lump these in with dynamic objects but those are a very different class of thing indeed.

Now, what would be -really- nice is if we had a way to specify that an anonymous type implements an interface. That could potentially simplify a -lot- of DTO modeling.

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