Question

Given this code:

List<string> things = new List<string>();

foreach (string thing in things)
{
    string foo = thing.ToUpper();
}

string foo = String.Empty;

Why does the compiler complain that foo is declared twice? Surely the instance declared in the foreach loop is only valid within the scope of the loop?

Answer 1

While you can only refer to the outer foo after you declared it, locals are allocated at the beginning of a function which means the inner foo will overshadow the outer one, even if it hasn’t been declared yet.