双引号是定义字符串的,如
string s1 = "abcdefg";
string[] ss = new string[]{"ab","cd","ef"};
单引号是定义单个字符的,如
char ch = 'a';
char[] chs = new char[]{'a','b','c'};
另外split 函数中用到的是char,即单引号的,而非双引号的.