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forÑ­»·C#ÓëC/C++µÄÐÔÄÜÇø±ð¡£ ÒÔC#ΪÀýµÄ3ÖÖÑ­»·£º int [] foo = new int[100]; Loop1: foreach(int i in foo)  Console.WriteLine(i.ToString()); Loop2: for(int i=0; i<foo.Length; i++)  Console.WriteLine(foo[i].ToString()); Loop3: int len=foo.Length; for(int i=0; i<len; i++)  Console.WriteLine(foo[i].ToString()); In C/C++, we know that compared to Loop3, Loop2 does not need compute the length of foo again and again. However, different with C/C++ the performance of Loop3 is worse than Loop2. C#code runs in a safe, managed enviroment. Every memory location is checked, including indexes. For Loop3: generated by complier: int len=foo.length; for(int i=0; i<len; i++) {  if(i<foo.Length)   Console.WriteLine(foo[i].ToString());  else   throw new IndexOutOfRangeException(); } ref: [Bill Wagner] Effective C#-50 Specific ways to improve Your C#.    Êղؠ  ·ÖÏí   ¶¥(1)

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Don¡®t try so hard, the best things come when you least expect them to.

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Get it ,the one more "if" may reduce the C# efficiency. I remember .  be in case of using it any more.

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