สอบถามเรื่องการใช้งานและการประยุกต์ไปใช้งานของ Dictionary (Collection)

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
	Dictionary<string, int> dictionary =
	    new Dictionary<string, int>();

	dictionary.Add("cat", 2);
	dictionary.Add("dog", 1);
	dictionary.Add("llama", 0);
	dictionary.Add("iguana", -1);
    }
}

using System.Collections.Generic;

class Program
{
    static void Main()
    {
	List<int> list = new List<int>();
	list.Add(2);
	list.Add(3);
	list.Add(5);
	list.Add(7);
    }
}

class Program
{
    static void Main()
    {
	// String arrays with 3 elements:
	string[] arr1 = new string[] { "one", "two", "three" };
	string[] arr2 = { "one", "two", "three" };
	var arr3 = new string[] { "one", "two", "three" };

	string[] arr4 = new string[3];
	arr4[0] = "one";
	arr4[1] = "two";
	arr4[2] = "three";
    }
}

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
	IEnumerable<int> result = from value in Enumerable.Range(0, 2)
				  select value;

	// Loop.
	foreach (int value in result)
	{
	    Console.WriteLine(value);
	}

	// We can use extension methods on IEnumerable<int>
	double average = result.Average();

	// Extension methods can convert IEnumerable<int>
	List<int> list = result.ToList();
	int[] array = result.ToArray();
    }
}

public class _UncerMulti
    {
        public double KeysValue; public double UncerValue;
        public double Multi()
        {
            return UncerValue / KeysValue;
        }
        public double MultiPow()
        {
            return System.Math.Pow(UncerValue / KeysValue,2);
        }
        public double MultiSqrt()
        {
            return System.Math.Sqrt(UncerValue / KeysValue);
        }
    }