Question

I am not sure how to use an extension method on a dictionary. How do I specify that I need the function applied to the value and not the key?

Here’s a sample code applying the Sum extension method on a list of doubles and a dictionary whose values are doubles. The list extension methods works fine but the dictionary extension method is asking for a selector function.

    static void Main(string[] args)
    {
        List<double> list = new List<double>();
        list.Add(34.2);
        list.Add(234);
        Console.WriteLine(list.Sum());

        Dictionary<string, double> dictioanary = new Dictionary<string, double>();
        dictioanary.Add("a", 5.34);
        dictioanary.Add("b", 44);

        Console.WriteLine(dictioanary.Sum());
        Console.ReadKey();
    }

Answer 1

You have to pass a lambda to the Sum() function:

Console.WriteLine(dictioanary.Sum(kvp => kvp.Value));