They aren't structural because the following doesn't work in C#, but would work (with tweaks to make it valid code) in a structurally typed language such as Typ

They aren't structural because the following doesn't work in C#, but would work (with tweaks to make it valid code) in a structurally typed language such as TypeScript: var transformed = media.Select(m => { var parts = m.Split('/'); return new { addedAtUtc = "2023-05-15T05:59:31.398Z", originTripUid = parts[4], path = $"{parts[4]}/{parts[5]}", rank = "", size = 103978, stored = true, type = "document", }; }).ToList(); transformed.AddRange(otherMedia.Select(m => { var parts = m.Split('/'); return new { addedAtUtc = "2023-05-15T05:59:31.398Z", originTripUid = parts[4], path = $"{parts[4]}/{parts[5]}", rank = "", size = 103978, stored = true, type = "document", documentType = parts[6] }; })); Adding "documentType" breaks in C# but would work in a structurally typed language as a structural type checker can see that the second result fulfills all of the necessary properties. Doing this in C# would require creating an interface and being explicit.