性能测试笔记

想比较 as , is , typeof , GetType , 强制类型转换这几个哪个性能更好。

以下是测试代码：

            object a = "hello";
            Stopwatch sw = Stopwatch.StartNew();
            sw.Restart();
            for (int i = 0; i < 10000; i++)
            {
                var d = a as string;
            }
            Console.WriteLine("As:" + sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < 10000; i++)
            {
                var d = (string)a;
            }
            Console.WriteLine("(string):" + sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < 10000; i++)
            {
                var d = a.GetType();
            }
            Console.WriteLine("GetType:" + sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < 10000; i++)
            {
                var d = typeof(string);
            }
            Console.WriteLine("typeof:" + sw.ElapsedTicks);

            for (int i = 0; i < 10000; i++)
            {
                var d = a is int;
            }
            Console.WriteLine("Is:" + sw.ElapsedTicks);

单元测试下Debug
第一次	第二次	第三次	平均
As:142	As:147	As:160	As:150
Is:157	Is:152	Is:177	Is:162
(string):146	(string):147	(string):165	(string):153
typeof:611	typeof:616	typeof:687	typeof:637
GetType:314	GetType:313	GetType:353	GetType:327

单元测试下Release
第一次	第二次	第三次	平均
As:21	As:20	As:20	As:20
Is:20	Is:20	Is:20	Is:20
(string):98	(string):98	(string):98	(string):98
typeof:20	typeof:20	typeof:20	typeof:20
GetType:333	GetType:333	GetType:348	GetType:339

Console程序Debug
第一次	第二次	第三次	平均
As:183	As:184	As:184	As:184
Is:295	Is:295	Is:411	Is:334
(string):231	(string):177	(string):241	(string):216
typeof:278	typeof:216	typeof:213	typeof:236
GetType:477	GetType:430	GetType:424	GetType:443

Console程序Release
第一次	第二次	第三次	平均
As:11	As:11	As:11	As:11
Is:6	Is:6	Is:6	Is:6
(string):45	(string):45	(string):45	(string):45
typeof:7	typeof:6	typeof:6	typeof:6
GetType:6	GetType:7	GetType:7	GetType:7

单元测试下，性能是不准的。

Release 下性能比较： is = typeof 高于 GetType 高于 As 高于强制类型转换。

----------------------------------------------------------

持续对以上结果表示怀疑，增加循环次数。

using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using MyCmn;
using System.Collections.Generic;
using System.Reflection;
using System.Reflection.Emit;
using System.Diagnostics;
using System.Threading;
using System.Linq;

namespace Test
{
    public class Main_Cls
    {
        const int TIMES = 100000;
        public static void Main()
        {
            object a = "hello world";
            var str = "hello world!";
            Stopwatch sw = Stopwatch.StartNew();

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = typeof(string);
            }
            MyConsole.WriteLine("typeof:", sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = a.GetType();
            }
            MyConsole.WriteLine("GetType:", sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = object.Equals(a, null);
            }
            MyConsole.WriteLine("object.Equals:", sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = default(string);
            }
            MyConsole.WriteLine("default:", sw.ElapsedTicks);

            MyConsole.WriteLine("String______________");
            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = "hello";
            }
            MyConsole.WriteLine("new string:", sw.ElapsedTicks);
            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = str.Length;
            }
            MyConsole.WriteLine("String.Length:", sw.ElapsedTicks);
            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = string.IsNullOrEmpty(str);
            }
            MyConsole.WriteLine("string.IsNullOrEmpty:", sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = a as string;
            }
            MyConsole.WriteLine("As:", sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = a is int;
            }
            MyConsole.WriteLine("Is:", sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = (string)a;
            }
            MyConsole.WriteLine("(string):", sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = i.ToString();
            }
            MyConsole.WriteLine("ToString:", sw.ElapsedTicks);
            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = i.AsString();
            }
            MyConsole.WriteLine("AsString:", sw.ElapsedTicks);


            MyConsole.WriteLine("                            ______________String");
            MyConsole.WriteLine("类型转换______________");

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = DateTime.Now;
            }
            MyConsole.WriteLine("DateTime:", sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = Guid.NewGuid();
            }
            MyConsole.WriteLine("Guid:", sw.ElapsedTicks);


            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = i.AsDecimal();
            }
            MyConsole.WriteLine("AsDecimal:", sw.ElapsedTicks);

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var d = i.AsFloat();
            }
            MyConsole.WriteLine("AsFloat:", sw.ElapsedTicks);
            MyConsole.WriteLine("                            ______________类型转换");

            sw.Restart();
            for (int i = 0; i < TIMES; i++)
            {
                var t = typeof(string).GetProperties();
            }
            MyConsole.WriteLine("Reflect:", sw.ElapsedTicks);
        }
    }

    public static class MyConsole
    {
        public static void WriteLine(string title, long msg = 0)
        {
            if (msg > 0)
            {
                Console.WriteLine(string.Format("{0,27} {1,-8}", title, msg));
            }
            else
            {
                Console.WriteLine(title);
            }
        }
    }
}

View Code

结果：

typeof: 45
GetType: 44
object.Equals: 1620
default: 44
String______________
new string: 45
String.Length: 45
string.IsNullOrEmpty: 900
As: 44
Is: 46
(string): 391
ToString: 53567
AsString: 146645
______________String
类型转换______________
DateTime: 35750
Guid: 69539
AsDecimal: 72932
AsFloat: 289442
______________类型转换
Reflect: 71428

As 的性能略高于 Is , 但判等的性能却是出忽意料的差。

再加入 == 判定测试和 a.Equals 的判定测试：

typeof: 58
GetType: 50
object.Equals: 1736
==: 49
a.Equals: 2420
default: 50
String______________
new string: 50
String.Length: 50
string.IsNullOrEmpty: 969
As: 50
Is: 50
(string): 441
ToString: 52179
AsString: 139356
______________String
类型转换______________
DateTime: 35400
Guid: 69725
AsDecimal: 82086
AsFloat: 321944
______________类型转换
Reflect: 63618

查看源码：

public static bool IsNullOrEmpty(string value)
{
    if (value != null)
    {
        return (value.Length == 0);
    }
    return true;
}