C# 转换关键字 operator

operator

使用 operator 关键字重载内置运算符，或在类或结构声明中提供用户定义的转换。

假设场景，一个Student类，有语文和数学两科成绩，Chinese Math，加减两科成绩，不重载运算，代码如下。

    class Student
    {
        /// <summary>
        /// 语文成绩
        /// </summary>
        public double Chinese { get; set; }

        /// <summary>
        /// 数学成绩
        /// </summary>
        public double Math { get; set; }
    }

比较两个成绩差距

			var a = new Student
            {
                Chinese = 90.5d,
                Math = 88.5d
            };

            var b = new Student
            {
                Chinese = 70.5d,
                Math = 68.5d
            };

            //a的语文比b的语文高多少分
            Console.WriteLine(a.Chinese - b.Chinese);
            //a的数学比b的数学高多少分
            Console.WriteLine(a.Math - b.Math);

使用operator 重载 -

    class Student
    {
        /// <summary>
        /// 语文成绩
        /// </summary>
        public double Chinese { get; set; }

        /// <summary>
        /// 数学成绩
        /// </summary>
        public double Math { get; set; }

        public static Student operator -(Student a, Student b)
        {
            return new Student
            {
                Chinese = a.Chinese - b.Chinese,
                Math = a.Math - b.Math
            };
        }
    }

比较成绩差距的代码可以改为

    class Program
    {
        static void Main(string[] args)
        {
            var a = new Student
            {
                Chinese = 90.5d,
                Math = 88.5d
            };

            var b = new Student
            {
                Chinese = 70.5d,
                Math = 68.5d
            };

            var c = a - b;
            //a的语文比b的语文高多少分
            Console.WriteLine(c.Chinese);
            //a的数学比b的数学高多少分
            Console.WriteLine(c.Math);
        }
    }

参考：运算符（C# 参考）