.NET：如何并行的从集合中返还元素？

实现代码

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using System.Threading;
 using System.Collections.Concurrent;

 namespace CSharpStudy.ParallelStudy
 {
     class HowToReturnList
     {
         public static void Error_Test()
         {
             var list = Enumerable.Range(, );

             var results = new List<string>();
             Parallel.ForEach(list, (item) =>
             {
                 results.Add("item:" + item);
             });

             Console.WriteLine(results.Count);
         }

         public static void Lock_Test()
         {
             var list = Enumerable.Range(, );

             var results = new List<string>();
             Parallel.ForEach(list, (item) =>
             {
                 lock (results)
                 {
                     results.Add("item:" + item);
                 }
             });

             Console.WriteLine(results.Count);
         }

         public static void Concurrent_Collections_Test()
         {
             var list = Enumerable.Range(, );

             var results = new ConcurrentQueue<string>();
             Parallel.ForEach(list, (item) =>
             {
                 lock (results)
                 {
                     results.Enqueue("item:" + item);
                 }
             });

             Console.WriteLine(results.Count);
         }

         public static void Task_Test()
         {
             var list = Enumerable.Range(, );

             var tasks = list.Select(item =>
             {
                 return Task.Run<string>(() =>
                 {
                     return "item:" + item;
                 });
             }).ToArray();
             Task.WhenAll(tasks);

             Console.WriteLine(tasks.Select(x => x.Result).Count());
         }

         public static void PLinq_Test()
         {
             var list = Enumerable.Range(, );

             var results = list.AsParallel().Select(item => "item:" + item);

             Console.WriteLine(results.Count());
         }
     }
 }