C# 少量字符串链接方法及测试（3）+=与StringBuilder

测试方法

使用+= 和StringBuilder 分别链接字符串10次，100次，1000次，100000次并计时使用 指定 capacity 和未指定capacity分别构造string builder 并循环10000000次测试环境为VS2017

结论

处理大量的字符串链接时，超过1000，string builder快。+= 的消耗是非线性的。处理少量字符串链接时，1000以内，不在意性能的情况下可以使用+=。当字符串超过16个以后，构建指定缓存区大小的string builder来链接字符串要快一些。

测试1 - Link strings by += - Total 10 - 1 += 0ms - 2 StringBuilder 0ms - Total 100 - 1 += 0ms - 2 StringBuilder 0ms - Total 1000 - 1 += 13ms - 2 StringBuilder 0ms - Total 10000 - 1 += 301ms - 2 StringBuilder 2ms - Total 100000 - 1 += 69806ms - 2 StringBuilder 21ms

测试2 - Link strings by += - Total 10 - 1 += 0ms - 2 StringBuilder 0ms - Total 100 - 1 += 0ms - 2 StringBuilder 0ms - Total 1000 - 1 += 11ms - 2 StringBuilder 0ms - Total 10000 - 1 += 166ms - 2 StringBuilder 1ms - Total 100000 - 1 += 43162ms - 2 StringBuilder 12ms

测试3 - String builder with default creator: 1895ms - String builder with capacity creator: 535ms - String builder with default creator: 1823ms - String builder with capacity creator: 577ms

Code1

var str = "+= i:0"; var sw = new System.Diagnostics.Stopwatch(); Console.WriteLine("Link strings by +="); for (var total = 10; total < 1000000; total *= 10) { Console.WriteLine("Total " + total.ToString()); sw.Reset(); sw.Start(); for (int i = 1; i < total; i++) { str += ", i:" + i.ToString(); } sw.Stop(); Console.WriteLine("1 += " + sw.ElapsedMilliseconds.ToString() + "ms"); var builder = new System.Text.StringBuilder(); builder.Append("+= i:0"); sw.Reset(); sw.Start(); for (int i = 1; i < total; i++) { builder.Append(", i:"); builder.Append(i.ToString()); } str = builder.ToString(); sw.Stop(); Console.WriteLine("2 StringBuilder " + sw.ElapsedMilliseconds.ToString() + "ms");

Code2

var sw = new System.Diagnostics.Stopwatch(); sw.Reset(); sw.Start(); for (var total = 10; total < 10000000; total++) { var builder = new System.Text.StringBuilder(); // 默认为缓冲16 builder.Append("string 1, length : 21"); // 创建32的缓冲区，并把原来的copy过来 builder.Append("string 2, length : 21"); // 创建64的缓冲区，并把原来的copy过来 } sw.Stop(); Console.WriteLine("String builder with default creator: " + sw.ElapsedMilliseconds.ToString() + "ms"); sw.Reset(); sw.Start(); for (var total = 10; total < 10000000; total++) { var builder = new System.Text.StringBuilder(64); // 直接创建64的缓冲区 builder.Append("string 1, length : 21"); builder.Append("string 2, length : 21"); } sw.Stop(); Console.WriteLine("String builder with capacity creator: " + sw.ElapsedMilliseconds.ToString() + "ms");