C# · 12月 29, 2021

c# – 为什么StringBuilder比字符串连接慢?

为什么StringBuilder与连接相比较慢?
StringBuilder旨在避免额外的对象创建,但是为什么会影响性能? static void Main(string[] args) { int max = 1000000; for (int times = 0; times < 5; times++) { Console.WriteLine(“\ntime: {0}”,(times+1).ToString()); Stopwatch sw = Stopwatch.StartNew(); for (int i = 0; i < max; i++) { string msg = “Your total is “; msg += “$500 “; msg += DateTime.Now; } sw.Stop(); Console.WriteLine(“String +\t: {0}ms”,((int)sw.ElapsedMilliseconds).ToString().PadLeft(6)); sw = Stopwatch.StartNew(); for (int j = 0; j < max; j++) { StringBuilder msg = new StringBuilder(); msg.Append(“Your total is “); msg.Append(“$500 “); msg.Append(DateTime.Now); } sw.Stop(); Console.WriteLine(“StringBuilder\t: {0}ms”,((int)sw.ElapsedMilliseconds).ToString().PadLeft(6)); } Console.Read(); }

编辑:根据建议移出范围变量:

解决方法 更改,以使StringBuilder不被实例化,而不是.Clear()它: time: 1String + : 3348msStringBuilder : 3151mstime: 2String + : 3346msStringBuilder : 3050ms

等等

请注意,这仍然测试完全相同的功能,但尝试重新使用资源一点更聪明.

代码:(也住在http://ideone.com/YuaqY)

using System;using System.Text;using System.Diagnostics;public class Program{ static void Main(string[] args) { int max = 1000000; for (int times = 0; times < 5; times++) { { Console.WriteLine(“\ntime: {0}”,(times+1).ToString()); Stopwatch sw = Stopwatch.StartNew(); for (int i = 0; i < max; i++) { string msg = “Your total is “; msg += “$500 “; msg += DateTime.Now; } sw.Stop(); Console.WriteLine(“String +\t: {0}ms”,((int)sw.ElapsedMilliseconds).ToString().PadLeft(6)); } { Stopwatch sw = Stopwatch.StartNew(); StringBuilder msg = new StringBuilder(); for (int j = 0; j < max; j++) { msg.Clear(); msg.Append(“Your total is “); msg.Append(“$500 “); msg.Append(DateTime.Now); } sw.Stop(); Console.WriteLine(“StringBuilder\t: {0}ms”,((int)sw.ElapsedMilliseconds).ToString().PadLeft(6)); } } Console.Read(); }}