Should variable declarations always be placed outside of a loop?

Question

Is it better to declare a variable used in a loop outside of the loop rather then inside? Sometimes I see examples where a variable is declared inside the loop. Does this ef

Answer 1

I am going to agree with most of these other answers with a caveat.

If you are using lambada expressions you must be careful with capturing variables.

static void Main(string[] args)
{
    var a = Enumerable.Range(1, 3);
    var b = a.GetEnumerator();
    int x;
    while(b.MoveNext())
    {
        x = b.Current;
        Task.Factory.StartNew(() => Console.WriteLine(x));
    }
    Console.ReadLine();
}

will give the result

3
3
3

Where

static void Main(string[] args)
{
    var a = Enumerable.Range(1, 3);
    var b = a.GetEnumerator();
    while(b.MoveNext())
    {
        int x = b.Current;
        Task.Factory.StartNew(() => Console.WriteLine(x));
    }
    Console.ReadLine();
}

will give the result

1
2
3

or some order there of. This is because when the task finally starts it will check the current value of it's reference to x. in the first example all 3 loops pointed at the same reference, where in the second example they all pointed at different references.