纳入泛型

Question

我正在使用C＃.net进行开发，我相信我需要使用泛型来解决我遇到的问题，但我不知道从哪里开始。

以下是我需要做的步骤：

1. 从用户处获取ID - DONE
2. 使用ID - DONE
查询数据库表
3. 拉回一行 - 完成
4. 创建依赖于ID的对象类型
5. 根据类型填充对象

不同的约会需要从数据库中拉回（填充）不同的信息。例如，一个约会可能只需要用户forename / surname，其他人可能需要forename / surname / dob。

我希望首先执行子类，然后调用父方法。问题是myAppointment在通过Switch语句后仍然被视为Appointment对象而不是DoctorAppointment / OtherAppointment。在声明myAppointment的地方，我实际上不知道它将是什么类型的对象

以下是我目前的代码：

        tblAppointment getAppointment = (from getApp in dc.tblAppointments
                                         where getApp.appID == Id
                                         select getApp).SingleOrDefault();

// Needs to be set the something. I really want this be to set to a generic type as I don’t really know what type it will be until it has been through the switch statement
Appointment myAppointment = null; 

            switch (getAppointment.tblAppointment.appTypeID)
            {
                case 2:
                    {
// Changes myAppointment from Appointment to DoctorsAppointment
                        myAppointment = new DoctorsAppointment();

                    }
                    break;
                case 1:
                    {
                        myAppointment = new OtherAppointment();
                    }
                    break;
                default:

                    break;

            }

// I want this to set myAppointment to DoctorsAppointment.Populate(getAppointment)
            return myAppointment.Populate(getAppointment);

约会是父类。 DoctorsAppointment / OtherAppointment是儿童班。

子类中的Populate需要一个参数，而父类则不需要。我目前收到的错误是：

No overload for method 'Populate' takes '1' arguments

希望我已经足够解释了自己。

谢谢，

克莱尔

Answer 1

一种解决方案是在父类Appointment中创建这样的方法：

public virtual void Populate( getAppointment) 
{
   // does nothing
}

然后在儿童班：

public override void Populate( getAppointment) 
{
// do what you need
}

Answer 2

听起来像是继承的案例

abstract class Appointment
{
    public abstract void Populate(AppointmentData data);
}

class DoctorsAppointment : Appointment
{
    public override void Populate(AppointmentData data)
    {
        // implementation specific to DoctorsAppointment
    }
}
class OtherAppointment : Appointment
{
    public override void Populate(AppointmentData data)
    {
        // implementation specific to OtherAppointment
    }
}

Answer 3

建议您采取上述继承答案之一

我认为你是否在使用LINQ to SQL是值得的？如果您有一个存储不同类型对象的表，则可以部分实现所需的功能。

请参阅here以获取示例

Answer 4

Appointment类应该声明适当的Populate方法。您还可以设置约会工厂类：

static class AppointmentFactory
{
    public static Appointment Create(int type) 
    {
        switch (type)
        {
            case 2:
                return new DoctorsAppointment();
            case 1:
                return new OtherAppointment();
            default:
                throw new AppointmentTypeNotSupportedException();
        }
    }
}

class Appointment
{
    public virtual void Populate(getAppointment data) { }
}

class DoctorsAppointment : Appointment
{
    public override void Populate(getAppointment data) {  }
}

class OtherAppointment : Appointment
{
    public override void Populate(getAppointment data) {  }
}

Answer 5

你应该将约会的Populate方法改为抽象（可能是虚拟的）并采用任何类型的getAppointment。子类DoctorsAppointment和OtherAppointment通过覆盖Appointment的默认值来实现Popuplate。

Answer 6

abstract class Appointment 
{
    public abstract string Populate(AppointmentData d);
}

class OtherAppointment : Appointment
{
    public override string Populate(AppointmentData d)
    {

    }
}

使Appointment成为一个抽象类，它不能自己实例化，并使populate方法也是抽象的，所以它必须由它的继承类实现