Why might a System.String object not cache its hash code?

Question

A glance at the source code for string.GetHashCode using Reflector reveals the following (for mscorlib.dll version 4.0):

public override unsafe int GetHashCo         


        

Answer 1

I may have made a wrong conclusion here, but isn't it true that while the string is immutable in the context of a .NET String object, it's still possible to change the value?

For instance, if you were so inclined to do this...

String example = "Hello World";

unsafe
{
    fixed (char* strPointer = myString) {
        strPointer[1] = 'a';
    }
} 

...wouldn't example still represent the same String object, but now with a value that would compute a different value for GetHashCode()? I may be off-base here, but since you could easily (if not pointlessly) do this, that would cause some issues as well.