在C#中将几个Parallel.ForEach合并为一个

using System;
using System.Collections.Generic;
using System.Threading.Tasks;

class Program
{
    static void Main(string[] args)
    {
        List<int> numbers = new List<int> { 1, 2, 3, 4, 5 };

        Task<List<int>> task1 = Task.Run(() =>
        {
            List<int> results = new List<int>();
            Parallel.ForEach(numbers, number =>
            {
                // 执行任务1的操作
                results.Add(number * 2);
            });
            return results;
        });

        Task<List<int>> task2 = task1.ContinueWith(previousTask =>
        {
            List<int> results = previousTask.Result;
            Parallel.ForEach(numbers, number =>
            {
                // 执行任务2的操作
                results.Add(number * 3);
            });
            return results;
        });

        Task<List<int>> task3 = task2.ContinueWith(previousTask =>
        {
            List<int> results = previousTask.Result;
            Parallel.ForEach(numbers, number =>
            {
                // 执行任务3的操作
                results.Add(number * 4);
            });
            return results;
        });

        // 等待最后一个任务完成并获取结果
        List<int> finalResults = task3.Result;

        // 输出结果
        foreach (int result in finalResults)
        {
            Console.WriteLine(result);
        }
    }
}