Comment by Timwi

> int is different to Integer

Having separate types for these is the problem; not the boxing. C#/IL/CLR handles boxing in a way that doesn't exhibit the problem. If your code is dealing with integers, they are never boxed. They are only boxed when you cast to a reference type such as object. As soon as you cast back to int, you are unboxing.

Java exhibits the problem in a big way because it doesn't have true generics, so you can't have (say) a list of integers or a dictionary with integer values, so they must always be boxed, so you need a separate “boxed integer” type to maintain type safety. In C# you can just use unboxed integers everywhere.