[C#/General] Enumerable.ToLookup 메서드 사용법

Enumerable.ToLookup 메서드 사용법

public class Example
{
    public static void Main()
    {
        Console.Write("<< Enumerable.ToLookup 출력 예제 >> \n");

        List<Production> productions =
            new List<Production> { new Production { Company = "A.Soft", Weight = 15.2, PhoneNumber = 0415236987 },
              new Production { Company = "B.Soft", Weight = 28.7, PhoneNumber = 021534789 },
              new Production { Company = "C.Soft", Weight = 8.0, PhoneNumber = 0651234569 },
              new Production { Company = "D.Soft", Weight = 12.3, PhoneNumber = 0140253698 },
              new Production { Company = "E.Soft", Weight = 15.8, PhoneNumber = 0854712586 } };

        ILookup<char, string> lookup =
            productions.ToLookup(p => p.Company[0], p => p.Company + " " + p.PhoneNumber);

        foreach (IGrouping<char, string> productGroup in lookup)
        {
            Console.WriteLine(productGroup.Key);
            foreach (string str in productGroup)
                Console.WriteLine("    {0}", str);
        }

        Console.WriteLine(System.Environment.NewLine);
        Console.WriteLine("Press any key to exit");
        Console.ReadKey();
    }
}

class Production
{
    public string Company { get; set; }
    public double Weight { get; set; }
    public long PhoneNumber { get; set; }
}