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

One of the reasons why there's no const correctness in C# is because it doesn't exist at the runtime level. Remember that C# 1.0 did not have any feature unless it was part of the runtime.

And several reasons why the CLR does not have a notion of const correctness are for example:

1. It complicates the runtime; besides, the JVM didn't have it either, and the CLR basically started as a project to create a JVM-like runtime, not a C++-like runtime.
2. If there is const correctness at the runtime level, there should be const correctness in the BCL, otherwise the feature is pretty much pointless as far as the .NET Framework is concerned.
3. But if the BCL requires const correctness, every language on top of the CLR should support const correctness (VB, JavaScript, Python, Ruby, F#, etc.) That's not going to happen.

Const correctness is pretty much a language feature only present in C++. So it pretty much boils down to the same argumentation as to why the CLR does not require checked exceptions (which is a Java language-only feature).

Also, I don't think you can introduce such a fundamental type system feature in a managed environment without breaking backward compatibility. So don't count on const correctness ever entering the C# world.