List<float> numbers = new List<float> { 43.68F, 1.25F, 583.7F, 6.5F };

float sum = numbers.AsQueryable().Sum();

Console.WriteLine("The sum of the numbers is {0}.", sum);

float?[] points = { null, 0, 92.83F, null, 100.0F, 37.46F, 81.1F };

float? sum = points.AsQueryable().Sum();

Console.WriteLine("Total points earned: {0}", sum);

class Package
{
    public string Company { get; set; }
    public double Weight { get; set; }
}

public static void SumEx3()
{
    List<Package> packages =
        new List<Package> 
            { new Package { Company = "Coho Vineyard", Weight = 25.2 },
              new Package { Company = "Lucerne Publishing", Weight = 18.7 },
              new Package { Company = "Wingtip Toys", Weight = 6.0 },
              new Package { Company = "Adventure Works", Weight = 33.8 } };

    // Calculate the sum of all package weights.
    double totalWeight = packages.AsQueryable().Sum(pkg => pkg.Weight);

    Console.WriteLine("The total weight of the packages is: {0}", totalWeight);
}

//引入命名空间
using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Linq;
using System.Reflection;

public class MainClass{
   public static void Main(){
            int[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
            var query = numbers.Sum();
   }
}

//引入命名空间
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class MainClass {
    public static void Main() {
        string[] words = { "cherry", "apple", "blueberry" };

        double totalChars = words.Sum(w => w.Length);

        Console.WriteLine("There are a total of {0} characters in these words.", totalChars);
    }
}