判断字符串是否为数字

  /// <summary>
        /// 判断字符串是否全部由数字组成
        /// </summary>
        /// <param name="str">字符串</param>
        /// <returns></returns>
        public static bool IsNum(String str)
        {
            if (str.Trim() == "")
            {
                return false;
            }
            if (str.IndexOf(".") == -1)
            {
                // 没有小数点
                return IsNumber(str);
            }
            else
            {
                // 存在小数点
                string[] strTemp = str.Split(".");
                if (strTemp.Length != 2)
                {
                    // 存在多个小数点，不是数字
                    return false;
                }
                // 对小数点分隔后的字符串进行判断
                foreach (string strSpilt in strTemp)
                {
                    if (IsNumber(strSpilt) == false)
                    {
                        return false;
                    }
                }
            }
            return true;
        }

        /// <summary>
        /// 判断字符串是否由数字组成
        /// </summary>
        /// <param name="str">字符串</param>
        /// <returns></returns>
        private static bool IsNumber(String str)
        {
            for (int i = 0; i < str.Length; i++)
            {
                if (Char.IsNumber(str, i) == false)
                {
                    return false;
                }
            }
            return true;
        }