C#: Why is this variable in scope and out of scope at the same time?

Question

Possible Duplicate:
C# Variable Scoping

I've run into something I've never encountered before. I'm not looking for a fix as I know how to solve it. What I'd like to know is what the compiler is doing. This is just example code:

if (true)
{
    int x = 0;
}
int x = 0;

That code produces the error "A local variable 'x' cannot be declared in this scope because it would give a different meaning to 'x'".

However, it I change the code to this:

if (true)
{
    int x = 0;
}
x = 0;

I get the error "Cannot resolve symbol 'x'".

So, what's going on here? How is it that x is both in scope and out of scope?

I've noticed this before and wondered about it. Personally I'm surprised the first doesn't compile, while it seems right that the second one should not compile. — Rob Levine, Mar 31 '11 at 16:46

Jon Skeet · Answer 1 · 2011-03-31T18:16:04.740

5

A variable's scope is the entire block in which it is declared. However, you can't refer to it until after the declaration.

Eric Lippert has a blog post on this which goes into more detail. EDIT: And as Eric points out, another one...

edited Mar 31 '11 at 18:16

answered Mar 31 '11 at 16:45

Jon Skeet

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You could just point them to a related answer from him :o)http://stackoverflow.com/questions/2049330/c-variable-scoping/2050864#2050864 – Matthew Whited Mar 31 '11 at 16:46
@Matthew: I knew there was a blog post; I didn't know Eric had answered an SO question. – Jon Skeet Mar 31 '11 at 16:48
Neither did I at first but I knew I saw the question before. – Matthew Whited Mar 31 '11 at 16:52
Thanks Jon; actually this article is more germane to the specific question: http://blogs.msdn.com/b/ericlippert/archive/2009/11/02/simple-names-are-not-so-simple.aspx – Eric Lippert Mar 31 '11 at 17:58

score 0 · Answer 2 · answered Mar 31 '11 at 16:47

0

Its not, simply because C# allows you to declare/define variables anywhere in the program its scope is the entire block in which it is declared ans so it is making the x predeclared/(in scope) for x in if block

answered Mar 31 '11 at 16:47

Shekhar_Pro

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C#: Why is this variable in scope and out of scope at the same time?

2 Answers2