Why are const parameters not allowed in C#?

Question

It looks strange especially for C++ developers. In C++ we used to mark a parameter as const in order to be sure that its state will not be changed in the method

Answer 1

I believe there are two reasons C# is not const-correct.

The first is understandibility. Few C++ programmers understand const-correctness. The simple example of const int arg is cute, but I've also seen char * const * const arg - a constant pointer to constant pointers to non-constant characters. Const-correctness on pointers to functions is a whole new level of obfuscation.

The second is because class arguments are references passed by value. This means there's already two levels of constness to deal with, without an obviously clear syntax. A similar stumbling point is collections (and collections of collections, etc).

Const-correctness is an important part of the C++ type system. It could - in theory - be added to C# as something that is only checked at compile-time (it doesn't need to be added to the CLR, and wouldn't affect the BCL unless the notion of const member methods were included).

However, I believe this is unlikely: the second reason (syntax) would be quite difficult to solve, which would make the first reason (understandibility) even more of a problem.