指针 for循环 foreach 以及 lamda 的性能比较.

var count = 10000 * 10000;

//几种写法
            /*
             * if (*pb++ == fn)
             * if (li[i] == fn)
             * if (i == fn)
             * li.First(j => j == fn);
*/

var li = new int[count];
for (var i = 0; i < count; i++)
            {
                li[i] = i;
            }
            count = li.Length;

var s = "";

var fn = li.Last();

var sw = new Stopwatch();

            sw.Start();

fixed (int* _pb = li)
            {
int* pb = _pb;

for (int i = 0; i < count; i++)
                {
if (*pb++ == fn)
break;
                }
            }

            s += "\r\n指针 \t" + sw.ElapsedMilliseconds;

            sw.Restart();

for (int i = 0; i < count; i++)
            {
if (li[i] == fn)
                {
break;
                }
            }

            s += "\r\nFor循环 \t" + sw.ElapsedMilliseconds;

            sw.Restart();
foreach (var i in li)
            {
if (i == fn)
                {
break;
                }
            }

            s += "\r\nForeach \t" + sw.ElapsedMilliseconds;

            sw.Restart();
            li.First(j => j == fn);

            s += "\r\nLamda \t" + sw.ElapsedMilliseconds;

            MessageBox.Show(s);

结果

 

 

 

指针直接访问内存,做的是最基础的运算,最快.

for循环 有下标 堆栈消耗+1

foreach Call NextElement 堆栈消耗 +1

lamda 用foreach 调用 func 堆栈消耗 +2