c# - Why am I getting wrong results when calling Func<int>?

Question

I have the following code snippet in C#:

var actions = new List<Func<int>>();

IEnumerable<int> values = new List<int> { 1, 2, 3 };

foreach (int value in values)
{
    actions.Add(() => value * value);
}

foreach (var action in actions)
{
    Console.WriteLine(action()); ;
}

Console.ReadLine();

It's running fine, but I am not getting the result I expect.

Actual result

9,9,9

Expected result

1,4,9

Why am I not getting the result I expect?

Answer 1

You need to capture the variable inside the loop. Right now your delayed execution actions are using the last value of value from the first foreach loop.

var actions = new List<Func<int>>();
        IEnumerable<int> values = new List<int> { 1, 2, 3 };
        foreach (int value in values)
        {
            var v = value;
            actions.Add(() => v * v);
        }
        foreach (var action in actions)
        {
            Console.WriteLine(action()); ;
        }
        Console.ReadLine();

Note the var v = value; line.