Why c# compiler generates a compile error?

Question

I have following code

using(some code)
{
var b = .... 
}
var b = ...

Erorr: A local variable named 'b' cannot be declared in this scope because it would give a different meaning to 'b', which is already used in a 'child' scope to denote something else

Ok, editing

using(some code)
{
var b = .... 
}
b = ...

Error: The name 'b' does not exist in the current context

Answer 1

can you do this?

for (int i = 0; i < 10; i++)
{
    int j = 1;
}
 int j = 2;

The answer is NO which means it pretty much consistent everywhere. Now it begs the question why. Answer to this question is It is illegal to have two local variables of the same name in the same local variable declaration space or nested local variable declaration spaces. And in the above case declaration of J is within the same nested scope.