> They really aren't, and they are IMHO an antipattern since they break encapsulation.

They don't. Java had to come up with the extremely verbose builder pattern for the exact same thing. And withers are basically the same tedious manual builder pattern, just with a different name.

For withers C# just has the with keyword: https://learn.microsoft.com/en-us/dotnet/csharp/language-ref...