將對象轉換為通用抽象類

Question

我來到這里的是一個像這樣的課程：

public abstract class SIBRegisterHardware2<T> : Register.IRegisterHardware<UInt16, UInt16> where T : IDevice
{
    protected T open()
    {
       // connect to server and return device T 
    }

    // ..
}

public class Device : SIBRegisterHardware2<IDevice>
{
    // ..
}

和一些派生類：

internal class DeviceA: SIBRegisterHardware2<IDeviceA>
{
}

internal class DeviceB: SIBRegisterHardware2<IDeviceB>
{
}

現在，我正在尋找一種允許我這樣做的解決方案：

if(createDevA == true) {
  Device<IDevice> devHandle = new DeviceA();
} else {
  Device<IDevice> devHandle = new DeviceB():
}

問題是這樣的代碼會產生如下錯誤：

Cannot implicitly convert type 'DeviceA' to 'SIBRegisterHardware2<IDevice>'

有沒有一種方法可以讓我抽象出這樣的模板？

---

我嘗試過的方法是創建另一個可以進行反射的類：

public class DeviceX : SIBRegisterHardware2<IDevice>
{
    private Register.IRegisterHardware<UInt16, UInt16> device = null;
    private Type deviceType = null;

    public DeviceX (String hwInterfaceClassName)
    {
        if (hwInterfaceClassName.Equals("DeviceA")) {

            device = new DeviceA();
            deviceType = device.GetType();
        }
        else if (hwInterfaceClassName.Equals("DeviceB")) {

            device = new DeviceB();
            deviceType = device.GetType();
        }
    }

    public override String doSomething(int param)
    {
        return (String)deviceType.GetMethod("doSomething").Invoke(device, new object[] { param }); ;
    }
}

但這是一個整潔的設計嗎？

Answer 1

對於SIBRegisterHardware2類型，應使用接口而不是抽象類。 然后，您可以在泛型中使用協方差 ：

public interface IDevice { }

public interface IDeviceA : IDevice { }
public interface IDeviceB : IDevice { }

public interface ISIBRegisterHardware2<out T> where T : class, IDevice
{
    void DoSomething();
}

internal class DeviceA : ISIBRegisterHardware2<IDeviceA>
{
    //...
}

internal class DeviceB : ISIBRegisterHardware2<IDeviceB>
{
    //...
}

if (createDevA == true)
{
    ISIBRegisterHardware2<IDevice> devHandle = new DeviceA();
}
else
{
    ISIBRegisterHardware2<IDevice> devHandle = new DeviceB();
}

更新0

public interface ISIBRegisterHardware2<out T> : Register.IRegisterHardware<UInt16, UInt16> where T : class, IDevice
{
    T Open();
}

public abstract class SIBRegisterHardware2<T> : ISIBRegisterHardware2<T> where T : class, IDevice
{
    T ISIBRegisterHardware2<T>.Open()
    {
        return OpenInternal();
    }

    protected virtual T OpenInternal()
    {
        //Common logic to open.
    }
}

internal class DeviceA : SIBRegisterHardware2<IDeviceA>
{
    //...
}

internal class DeviceB : SIBRegisterHardware2<IDeviceB>
{
    //...
}

ISIBRegisterHardware2<IDevice> devHandle;
if (createDevA == true)
{
    devHandle = new DeviceA();
}
else
{
    devHandle = new DeviceB();
}
devHandle.Open();