Why c# compiler generates a compile error? [duplicate]

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

"The local variable declaration space of a block includes any nested blocks. Thus, within a nested block it is not possible to declare a local variable with the same name as a local variable in an enclosing block." Variable Scopes, MSDN