What does => mean in a Linq Expression [duplicate]

Answer 1

To better understand this. I would rewrite your code without LINQ as below:

public static class Extend
    {
        public static double StandardDeviation(this IEnumerable values)
        {
            double avg = values.Average();
            var newValues = new List();
            foreach (var v in values)
            {
                newValues.Add(Math.Pow(v - avg, 2));
            }

            return Math.Sqrt(newValues.Average());
        }
    }

Now you can compare these two versions of code and see the relation.