Some sample about lambda

lambda.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
 
namespace WindowsFormsApplication1
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            List<string> myStringLists = new List<string>();
            myStringLists.Add("1145");
            myStringLists.Add("22");
            myStringLists.Add("1");
            myStringLists.Add("55");
            myStringLists.Add("519");
            List<int> retList = new List<int>();
            retList = GetSquaresOfPositiveByLambda(myStringLists);
/////
            
 
            string[] days = { "ass", "asdasd", "bbsd", "ass", "www", "bbs", "ee", "sss", "wwss"};
            Dictionary<char, List<string>> s1 = GetIndex(days);
            Dictionary<char, List<string>> s2 = GetIndexByLambda(days);
 
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
        static List<int> GetSquaresOfPositiveByLambda(List<string> strList)
        {
            return strList
                .Select(s => Int32.Parse(s)) // 转成整数
                .Where(i => i % 2 == 0) // 找出所有偶数
                .Select(i => i * i) // 算出每个数的平方
                .OrderBy(i => i) // 按照元素自身排序
                .ToList(); // 构造一个List
        }
 
        static Dictionary<char, List<string>> GetIndexByLambda(IEnumerable<string> keywords)
        {
            return keywords
                .GroupBy(k => k[0])
                .ToDictionary(
                    g => g.Key,
                    g => g.OrderBy(k => k).ToList());
        }
 
        static Dictionary<char, List<string>> GetIndex(IEnumerable<string> keywords)
        {
            // 定义字典
            var result = new Dictionary<char, List<string>>();
 
            // 填充字典
            foreach (var kw in keywords)
            {
                var firstChar = kw[0];
                List<string> groupKeywords;
 
                if (!result.TryGetValue(firstChar, out groupKeywords))
                {
                    groupKeywords = new List<string>();
                    result.Add(firstChar, groupKeywords);
                }
 
                groupKeywords.Add(kw);
            }
 
            // 为每个分组排序
            foreach (var groupKeywords in result.Values)
            {
                groupKeywords.Sort();
            }
 
            return result;
        }
    }
}