using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public class Test

    {

        public Status St {get;set;}

    }

    public enum Status

    {

        One = 1,

        Two = 2,

        Three = 3,

        Four = 4

    }

    public static Test GetTest()

    {

        return null;

    }

    public class TestDict

    {

        public int I {get;set;}

        public string S{get;set;}

    }

    public static void PrintArr(int[] arr)

    {

        foreach(var a in arr)

            Console.Write($"{a} ");

        Console.WriteLine();

    }

    public class Test2

    {

        public string Name{get;set;}

        public int Type {get;set;}

    }

    public static void Main()

    {

        List<Test2> dict2 = new List<Test2>{new Test2{Name="Name1", Type=1},new Test2{Name="Name2", Type=1}, new Test2{Name="Name3",Type=2}};

        var kk = dict2.GroupBy(x=>x.Type);

        foreach (var k in kk)

        {

            Console.WriteLine(k.Key);

            foreach (var k1 in k)

            {

                Console.WriteLine(k1.Name);

            }

        }

        var arr1 = new int[]{1,2,3};

        var arr2 = arr1;

        arr1[2] = 4;

        PrintArr(arr1);

        PrintArr(arr2);

        var arrT = new int[0];

        Console.WriteLine(arrT.Any());

        var dict = new Dictionary<int, TestDict>

        {

            {1, new TestDict

                {

                    I=1,

                    S="one"

                }

            },

            {2, new TestDict

                {

                    I=2,

                    S="two"

                }

            }

        };

        var list = new List<int>{1,2,3};

        list.ForEach(l=>{

            if (dict.TryGetValue(l, out var v))

            {

                Console.WriteLine(v.I);

            }

            else

            {

                Console.WriteLine("error");

            }

            if (v != null)

                Console.WriteLine(v.S);

        });

        var t = GetTest();

        switch (t?.St)

        {

            case null:

            case Status.One:

                Console.WriteLine("nullOrone");

                break;

            default:

                Console.WriteLine("default");

                break;

        }

        Console.WriteLine("Hello World");

    }

}