字符串之Raplace函数的实现

 //这是普通的repalce的方法，不知道c#中的string如何实现的
        public static string Repalce(string str, string oldValue, string newValue)
        {
            for (int i = 0; i < str.Length - oldValue.Length; i++)
            {
                if (str.Substring(i, oldValue.Length) == oldValue)
                {
                    string forStr = str.Substring(0, i);
                    string afterStr = str.Substring(i + oldValue.Length);
                    str = forStr + newValue + afterStr;
                    i = i + newValue.Length - 1;
                }
            }
            return str;
        }

        //递归实现
        public static string RepalceD(string Str, string oldValue, string newValue)
        {
            int index = Str.IndexOf(oldValue);
            if (index == -1)
            {
                return Str;
            }
            else
            {
                return Str.Substring(0, index) + newValue + RepalceD(Str.Substring(index + oldValue.Length), oldValue, newValue);
            }
        }