Add .NET 9 中 LINQ 新增的功能

Author: YSGStudyHards

DotNetGuidePractice/HelloDotNetGuide/CSharp语法/LinqExercise.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace HelloDotNetGuide.CSharp语法
+{
+    public class LinqExercise
+    {
+        #region .NET 9 中 LINQ 新增的功能
+
+        //public static void CountByExample()
+        //{
+        //    //这里wordCounts是一个字典，包含每个单词及其出现次数的键值对
+        //    var sourceText = "This is a test text. This is only a test. This is the best. This，This，This";
+        //    KeyValuePair<string, int> mostFrequentWord = sourceText
+        //    .Split(new char[] { ' ', '.', ',' }, StringSplitOptions.RemoveEmptyEntries)
+        //    .Select(word => word.ToLowerInvariant())
+        //    .CountBy(word => word)
+        //    .MaxBy(pair => pair.Value);
+
+        //    Console.WriteLine($"最常见的词是：'{mostFrequentWord.Key}'  {mostFrequentWord.Value}");
+        //}
+
+        //public static void AggregateByExample()
+        //{
+        //    (string id, int score)[] data =
+        //        [
+        //            ("0", 88),
+        //        ("1", 5),
+        //        ("2", 4),
+        //        ("1", 10),
+        //        ("6", 5),
+        //        ("4", 10),
+        //        ("6", 25)
+        //        ];
+
+        //    // aggregatedData 是一个序列，包含按姓名分组并计算总分的元素
+        //    var aggregatedData =
+        //        data.AggregateBy(
+        //            keySelector: entry => entry.id,
+        //            seed: 0,
+        //            (totalScore, curr) => totalScore + curr.score
+        //            );
+
+        //    foreach (var item in aggregatedData)
+        //    {
+        //        Console.WriteLine(item);
+        //    }
+        //}
+
+        //public static void IndexExample()
+        //{
+        //    var lines = new List<string> { "First line", "Second line", "Third line" };
+        //    foreach (var (index, line) in lines.Index())
+        //    {
+        //        Console.WriteLine($"Line {index + 1}: {line}");
+        //    }
+        //}
+
+        #endregion
+    }
+}