C# 使用运算符重载 简化结果判断

　　执行某个方法后, 一般都要对执行结果判断, 如果执行不成功, 还需要显示错误信息, 我先后使用了下面几种方式

        /// <summary>
        /// 返回int类型结果, msg输出错误信息
        /// </summary>
        /// <param name="param">输入参数</param>
        /// <param name="msg">错误信息</param>
        /// <returns>0-成功, 其他值-失败</returns>
        public int Foo(object param, out string msg);

        /// <summary>
        /// 直接返回值(string)为空, 表示成功; 不成功的话, 输出错误信息
        /// </summary>
        /// <param name="param">输入参数</param>
        /// <param name="result">结算结果</param>
        /// <returns>null或者""(string.Empty)-成功, 非空-失败</returns>
        public string Bar(object param, out object result);

        public struct Result
        {
            /// <summary>
            /// 执行结果
            /// </summary>
            public int Code;

            /// <summary>
            /// 错误信息
            /// </summary>
            public string Msg;
        }

        /// <summary>
        /// 直接返回Result结果, Result.Code表示执行结果, Result.Msg包含错误信息
        /// </summary>
        /// <param name="param"></param>
        /// <param name="calculateResult"></param>
        /// <returns>Result.Code表示执行结果, Result.Msg包含错误信息</returns>
        public Result Baz(object param, out object calculateResult);


        public void Test()
        {
            object calculateResult;
            var result = Baz(null, out calculateResult);
            if (result.Code!=0)
            {
                // ...
            }
        }

　　第3种方法, 每次判断都需要键入Code, 有点麻烦, 可以使用C#的运算符重载简化一点点代码

    /// <summary>
    /// 带结果代码和提示信息的结构体, 可以很方便的以结果代码(Code)与int比较, Code==0表示成功
    /// </summary>
    public struct Result
    {
        /// <summary>
        /// 结果代码
        /// </summary>
        public int Code;

        /// <summary>
        /// 提示信息
        /// </summary>
        public string Msg;



        #region 构造函数

        public Result(string msgParam)
            : this(-1, msgParam)
        { }


        public Result(int codeParam, string msgParam)
        {
            Code = codeParam;
            Msg = msgParam;
        }

        #endregion



        #region 快速生成结构体
        public static Result Pass { get { return new Result(); } }


        public static Result PassWithMsg(string msgParam)
        {
            return new Result() { Code = 0, Msg = msgParam };
        }


        public static Result Fail(string msgParam)
        {
            return new Result(msgParam);
        }

        //如果codeParam==0 的话, 强制变 -1
        public static Result Fail(int codeParam, string msgParam)
        {
            codeParam = codeParam == 0 ? -1 : codeParam;
            return new Result(codeParam, msgParam);
        }
        #endregion



        #region 重载与int的比较

        public static bool operator ==(int lhs, Result rhs)
        {
            return lhs == rhs.Code;
        }

        public static bool operator !=(int lhs, Result rhs)
        {
            return lhs != rhs.Code;
        }

        public static bool operator ==(Result lhs, int rhs)
        {
            return rhs == lhs;
        }

        public static bool operator !=(Result lhs, int rhs)
        {
            return rhs != lhs;
        }
        #endregion



        #region 还得实现同类型的比较

        public static bool operator ==(Result lhs, Result rhs)
        {
            return lhs.Code == rhs.Code;
        }

        public static bool operator !=(Result lhs, Result rhs)
        {
            return lhs.Code != rhs.Code;
        }
        #endregion



        #region 按要求重载 Equals()和GetHashCode()两个方法, 完全以Code为比较值

        public override bool Equals(object obj)
        {
            if (obj is int)
            {
                return this.Code == (int)obj;
            }
            if (obj is Result == false)
            {
                return false;
            }
            return this.Code == ((Result)obj).Code;
        }

        public override int GetHashCode()
        {
            return this.Code.GetHashCode();
        }

        #endregion




        #region int显示转换为Result结构(示例: Result result=(Result)0;  ), 弃用这个的原因是: 当结果不为0时, 不能赋值Msg;
        //public static explicit operator Result(int result)
        //{
        //    return new Result() { Code = result };
        //}
        #endregion
    }

　　这样的话, 就不用每次都输入Code了

    class Program
    {
        static void Main(string[] args)
        {
            var result = PassMethod();
            if (result==0)  //直接与int比较
            {
                Console.WriteLine("PassMethod成功");
            }
            else
            {
                Console.WriteLine("PassMethod失败: "+result.Msg);
            }


            result = FailMethod();
            if (result == Result.Pass) //与Result类型比较
            {
                Console.WriteLine("FailMethod成功");
            }
            else
            {
                Console.WriteLine("FailMethod失败: " + result.Msg);
            }
        }


        public static Result PassMethod()
        {
            return Result.Pass;
        }

        public static Result FailMethod()
        {
            return Result.Fail("Something is wrong");
        }
    }