string str1="i want to eat an apple"; string str2="i want eat apple"; Console.WriteLine(str1.Length); Console.Write(str2.Length); Console.ReadKey();第一个长度是...谢谢，那我怎么知道少了什么呢。。。string[] aa;string[] bb; string str1="i want to eat an apple"; string str2="i want eat apple"; aa = str1.Split(' '); bb = str2.Split(' '); int count=0; foreach(string c in aa) { count = 0; for (int i = 0; i < bb.Length; i++) { if (c != bb[i]) { count++;} if (count == bb.Length) { Console.Write(c+' '); } } }Console.ReadKey();已经把to和an两个缺失的单词在控制台输出了。你拿去用吧。