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法律研究C# 中的 Foreach 和 Parallel.Foreach 有什么区别？
C# 中的 Foreach 循环在单线程上运行，处理按顺序一个接一个进行。而 C# 中的 Parallel.Foreach 循环则在多线程上运行，并行地进行处理。这意味着它会一次性地遍历所有项而无需等待之前的项完成。
Parallel.Foreach 的执行速度比普通 ForEach 要快。要使用 Parallel.ForEach 循环，我们需要导入 System.Threading.Tasks 命名空间。
示例
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
namespace DemoApplication{
class Demo{
static void Main(string[] args){
var animals = new List<string>{
"cat", "rat", "deer", "elephant", "lion", "tiger", "dog", "pig", "buffalo", "rabbit", "horse", "cheetah", "cow", "goat", "sheep", "donkey", "zebra", "wolf", "fox", "lepoard", "monkey", "kangaroo", "girafee", "hippo"
};
var stopWatch = Stopwatch.StartNew();
foreach (string animal in animals){
Console.WriteLine($"Fruit Name: {animal}, Thread Id={Thread.CurrentThread.ManagedThreadId}");
}
Console.WriteLine($"foreach loop execution time = {stopWatch.Elapsed.TotalSeconds} seconds");
var stopWatch2 = Stopwatch.StartNew();
Parallel.ForEach(animals, animal =>{
Console.WriteLine($"Fruit Name: {animal}, Thread Id={Thread.CurrentThread.ManagedThreadId}");
});
Console.WriteLine($"Parallel foreach loop execution time = {stopWatch2.Elapsed.TotalSeconds} seconds");
Console.ReadLine();
}
}
}输出
以上代码的输出为
Fruit Name: cat, Thread Id= 1 Fruit Name: rat, Thread Id= 1 Fruit Name: deer, Thread Id= 1 Fruit Name: elephant, Thread Id= 1 Fruit Name: lion, Thread Id= 1 Fruit Name: tiger, Thread Id= 1 Fruit Name: dog, Thread Id= 1 Fruit Name: pig, Thread Id= 1 Fruit Name: buffalo, Thread Id= 1 Fruit Name: rabbit, Thread Id= 1 Fruit Name: horse, Thread Id= 1 Fruit Name: cheetah, Thread Id= 1 Fruit Name: cow, Thread Id= 1 Fruit Name: goat, Thread Id= 1 Fruit Name: sheep, Thread Id= 1 Fruit Name: donkey, Thread Id= 1 Fruit Name: zebra, Thread Id= 1 Fruit Name: wolf, Thread Id= 1 Fruit Name: fox, Thread Id= 1 Fruit Name: lepoard, Thread Id= 1 Fruit Name: monkey, Thread Id= 1 Fruit Name: kangaroo, Thread Id= 1 Fruit Name: girafee, Thread Id= 1 Fruit Name: hippo, Thread Id= 1 foreach loop execution time = 0.0129221 seconds Fruit Name: cat, Thread Id= 1 Fruit Name: rat, Thread Id= 1 Fruit Name: deer, Thread Id= 1 Fruit Name: elephant, Thread Id= 1 Fruit Name: lion, Thread Id= 1 Fruit Name: tiger, Thread Id= 1 Fruit Name: pig, Thread Id= 1 Fruit Name: buffalo, Thread Id= 1 Fruit Name: dog, Thread Id= 3 Fruit Name: sheep, Thread Id= 3 Fruit Name: donkey, Thread Id= 3 Fruit Name: rabbit, Thread Id= 1 Fruit Name: goat, Thread Id= 5 Fruit Name: fox, Thread Id= 5 Fruit Name: lepoard, Thread Id= 5 Fruit Name: cow, Thread Id= 4 Fruit Name: hippo, Thread Id= 4 Fruit Name: kangaroo, Thread Id= 9 Fruit Name: girafee, Thread Id= 6 Fruit Name: monkey, Thread Id= 5 Fruit Name: horse, Thread Id= 1 Fruit Name: cheetah, Thread Id= 1 Fruit Name: zebra, Thread Id= 3 Fruit Name: wolf, Thread Id= 3 Parallel foreach loop execution time = 0.0092988 seconds
从以上结果中，我们可以看出，Parallel.Foreach 在不同的线程中执行，并且与普通 foreach 相比耗时更少。
更新于：04-8-2020
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