Why doesn't C# offer constness akin to C++?

Question

References in C# are quite similar to those on C++, except that they are garbage collected.

Why is it then so difficult for the C# compiler to support the following:

Answer 1

The question is, do we need constness in C#?

1. I'm pretty sure that the JITter knows that the given method is not going to affect the object itself and performs corresponding optimizations automagically. (maybe by emitting call instead of callvirt ?)

2. I'm not sure we need those, since most of the pros of constness are performance related, you end up at the point 1.

Besides that, C# has the readonly keyword.