C#继承和转换

Question

我有以下代码,我得到以下异常"InvalidCastException:无法将'Employee'类型的对象强制转换为'EmployeeProfile'."

    private class Employee
    {
        public string Name { get; private set; }

        public Employee()
        {
            this.Name = "employee";
        }

        public override string ToString()
        {
            return this.Name;
        }
    }

    private class EmployeeProfile : Employee
    {
        public string Profile { get; private set; }

        public EmployeeProfile() : base()
        {
            this.Profile = string.Format("{0}'s profile", this.Name);
        }

        public override string ToString()
        {
            return this.Profile;
        }
    }

    public void RunTest()
    {
        Employee emp = new Employee();
        EmployeeProfile prof = (EmployeeProfile)emp; // InvalidCastException here

        System.Console.WriteLine(emp);
        System.Console.WriteLine(prof);
    }

也许我的大脑已经烧坏了,但我认为你可以将一个子类型转换为它的基类型？我在这里错过了什么？也许是假期......谢谢!

Answer 1

您可以将子类型转换为其基类型.但是您要将基类型的实例转换为子类型.

EmployeeProfile是一名员工.不一定相反.

因此,这将工作:

EmployeeProfile prof = new EmployeeProfile();
Employee emp = prof;

然而,这个模型充满了糟糕的设计.员工档案不是一种特殊的员工,是吗？员工拥有个人资料更有意义.你是在这里的组成模式.

Answer 2

所有的答案都是正确的...只是提供一个简单的简单解释......

class Employee

class Female : Employee

class Male: Employee

只是因为你是一个Employee不会让你成为Female......