.NET 9 中 LINQ 新增功能实现过程

        public static void CountByExample()
        {
            var sourceText = "This is a test text. This is only a test. This is the best. This，This，This";
            // 统计每个单词出现的次数
            KeyValuePair<string, int> mostFrequentWord = sourceText
            .Split([' ', '.', ','], StringSplitOptions.RemoveEmptyEntries)
            .Select(word => word.ToLowerInvariant())
            .CountBy(word => word)
            .MaxBy(pair => pair.Value);
            Console.WriteLine($"最常见的词是：'{mostFrequentWord.Key}' 出现次数： {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}");
            }
        }