当对函数的返回值有多种需求时（执行是否成功，及业务数据的返回值），可采用的方法

（1）bool+out

（2）返回值为实体模式：
 public  class DiskResult
    {
        private bool successful;
        private string result;
        private string errorMessage;

        public bool Successful
        {
            get
            {
                return successful;
            }

            set
            {
                successful = value;
            }
        }

        public string Result
        {
            get
            {
                return result;
            }

            set
            {
                result = value;
            }
        }

        public string ErrorMessage
        {
            get
            {
                return errorMessage;
            }

            set
            {
                errorMessage = value;
            }
        }