class Salary
{
    public int RMB { get; set; }

    public static Salary operator +(Salary s1, Salary s2)
    {
        return new Salary { RMB = s1.RMB + s2.RMB };
    }
}

//调用
Salary mikeIncome = new Salary { RMB = 10 };
Salary roseIncome = new Salary { RMB = 11 };
Salary familyIncome = mikeIncome + roseIncome;