/// <summary>

        /// ToInt

        /// </summary>

        /// <param name="str"></param>

        /// <returns></returns>

        public static int atoi(string str)

        {

            string strNew = str.Trim();

            string ch = strNew.Substring(0, 1);

            string result = "";

            int bl = 0;

            double re;

            bool flag = true;

            for (int i = 1; i < strNew.Length; i++)

            {

                string s = strNew.Substring(i, 1);

                if (int.TryParse(s, out bl))

                {

                    if (Convert.ToInt32(s) == 0)

                        continue;

                    switch (ch)

                    {

                        case "0":

                            result = result + s.ToString();

                            break;

                        case "+":

                            result = result + s.ToString();

                            break;

                        case "-":

                            flag = false;

                            result = result + s.ToString();

                            break;

                        default:

                            if (i == 1)

                                result = result + ch.ToString();

                            result = result + s.ToString();

                            break;

                    }

                }

                else

                    break;

            }

            if (!string.IsNullOrEmpty(result))

            {

                re = Convert.ToDouble(result);

                if (!flag)

                    re = -re;

                if (re < int.MinValue || re > int.MaxValue)

                    re = 0;

            }

            else

                re = 0;

            return (int)re;

        }

static void Main(string[] args)

        {

            Console.WriteLine("请输入要转化的字符串：");

            string str = Console.ReadLine();

            int re = atoi(str);

            if (re != 0)

                Console.WriteLine("转化后：" + re);

            else

                Console.WriteLine("该字符串不能转换为整数！");

            Console.ReadKey();

        }