c# 截取字符串两特定字符中间的字符

string str = "abcdefg";

string stra = "a";

string strg = "g";

int start = str.IndexOf(stra);

int end = str.IndexOf(strg);

string date = str.Substring (start + 1 ,end - start - 1);

则结果为 date = bcdef;