C＃中的变量范围，Java

Question

No, this is not my homework.
(Because there is a stack of answer sheets beside me, waiting to be marked.)

Q: If a local variable in a method has the same name as a variable in the main program, what will occur?
a) an error is generated
b) the variable in the main program is "hidden" until the method is finished executing
c) the variable in the main program will override the variable from the method
d) None of the above.

And the textbook answer is b, quite straightforward.

But on a second thought, is it really "hidden"?
As far as I know, in pure object-oriented languages like C# and Java,
we can always use

this.x

or

MainProgram.x

for static variables.

So my question is:
Can option b be considered true for C#? Why?

Please share your thoughts.

Answer 1

Yes, the local variable x hides (or more precisely, shadows - thanks to @pst) the member variable x within the scope of that method / block. You can refer to the latter with its qualified name as this.x , to make life easier, but nevertheless the answer is correct. A (fully) qualified name is not scope-dependent anymore so it can't be hidden or shadowed.

Answer 2

I refer you to section 3.7.1 of the C# 4 specification, the beginning of which I quote here for your convenience:

The scope of an entity typically encompasses more program text than the declaration space of the entity. In particular, the scope of an entity may include declarations that introduce new declaration spaces containing entities of the same name. Such declarations cause the original entity to become hidden . Conversely, an entity is said to be visible when it is not hidden .

Correctly understanding this portion of the specification requires that you understand the difference between the scope of an entity and its declaration space . The scope is the region of program text in which the entity may be referred to by its unqualified name. The declaration space is the region of program text in which an entity's name is unique.

Read the rest of section 3.7.1 for the details.

I note also that the specified term is "hidden", though "shadowed" is also frequently used.