All I want to do is make sure that child classes of the class Item implement a static method and I want this to be checked at compile time to avoid runtime errors.
abstract classes with static methods don't seem to work:
ERROR: A static member cannot be marked as override, virtual, or abstract
public abstract class Item
{
public static abstract Item GetHistoricalItem(int id, DateTime pastDateTime);
}
public class Customer : Item
{
public static override Customer GetHistoricalItem(int id, DateTime pastDateTime)
{
return new Customer();
}
}
public class Address : Item
{
public static override Address GetHistoricalItem(int id, DateTime pastDateTime)
{
return new Address();
}
}
and interfaces don't seem to work either:
ERROR: Customer does not implement interface member GetHistoricalItem()
public class Customer : Item, HistoricalItem
{
public static Customer GetHistoricalItem(int id, DateTime pastDateTime)
{
return new Customer();
}
}
public class Address : Item, HistoricalItem
{
public static Address GetHistoricalItem(int id, DateTime pastDateTime)
{
return new Address();
}
}
interface HistoricalItem
{
Item GetHistoricalItem();
}
Is there some workaround for this to have the compiler check if inheriting classes implement a static method with a certain signature or not?
There is a workaround i figured out for your scenario:
public class Customer : Reference<Customer>, IHistoricalItem
{
}
public class Address : Reference<Address>, IHistoricalItem
{
}
public interface IHistoricalItem
{
}
public class Reference<T> where T : IHistoricalItem, new()
{
public static T GetHistoricItem(int id, DateTime pastDateTime)
{
return new T();
}
}
Hope this helps!!
This cannout be done.
Have a look at Why can't I have abstract static methods in c#?
It doesn't make sense to force clients to implement a static method - static methods are "immutable." (There's probably a better way to describe them but that's all my mind can come up with right now!)
If some sort of overriding is required, I would consider re-visiting the design, possibly using some form of a combination of singletons and injection.
看起来不可能,看看: 有没有办法强制C#类实现某些静态函数?
根据定义,静态方法不能在派生类中实现。
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