[英]C# - list of subclass Types
I'd like to have a List of Class Types (not a list of Class instances) where each member of the List is a Subclass of MyClass. 我想要一个类类型列表(不是类实例列表),其中List的每个成员都是MyClass的子类。
For example, i can do this: 例如,我可以这样做:
List<System.Type> myList;
myList.Add(typeof(mySubClass));
but i'd like to restrict the list to only accept subclasses of MyClass. 但我想限制列表只接受MyClass的子类。
This is distinct from questions like this . 这与此类问题截然不同。 Ideally i'd like to avoid linq, as it's currently unused in my project.
理想情况下,我想避免linq,因为它在我的项目中目前尚未使用。
Servy is right in his comment , and Lee in his : it's much more preferable to compose than inherit . Servy在他的评论中是正确的 , Lee 在他的评论 中 : 组合比继承更为可取 。 So this is a good option:
所以这是一个很好的选择:
public class ListOfTypes<T>
{
private List<Type> _types = new List<Type>();
public void Add<U>() where U : T
{
_types.Add(typeof(U));
}
}
Usage: 用法:
var x = new ListOfTypes<SuperClass>();
x.Add<MySubClass>()
Note that you can make this class implement an interface like IReadOnlyList<Type>
if you want to give other code read access to the contained Type
s without other code having to depend on this class. 请注意,如果要为其他代码提供对包含的
Type
的读访问权,而不需要依赖此类的其他代码,则可以使此类实现类似IReadOnlyList<Type>
的接口。
But if you want to inherit anyway, you could create your own class that inherits from List
, then add your own generic Add
method like this: 但是如果你想继承,你可以创建自己继承自
List
的类,然后添加你自己的通用Add
方法,如下所示:
public class ListOfTypes<T> : List<Type>
{
public void Add<U>() where U : T
{
Add(typeof(U));
}
}
Just be aware of what Lee said : with this second version you can still Add(typeof(Foo))
. 只要知道Lee说的话 :用第二个版本你仍然可以
Add(typeof(Foo))
。
You should derive a list class from List and override the Add method to perform the type checking that you need. 您应该从List派生一个列表类,并覆盖Add方法以执行您需要的类型检查。 I'm not aware of a way in .NET to do that automatically.
我不知道在.NET中自动执行此操作的方法。
Something like this could work: 像这样的东西可以工作:
public class SubTypeList : List<System.Type>
{
public System.Type BaseType { get; set; }
public SubTypeList()
: this(typeof(System.Object))
{
}
public SubTypeList(System.Type baseType)
{
BaseType = BaseType;
}
public new void Add(System.Type item)
{
if (item.IsSubclassOf(BaseType) == true)
{
base.Add(item);
}
else
{
// handle error condition where it's not a subtype... perhaps throw an exception if
}
}
}
You would need to update the other methods that add/update items to the list (index setter, AddRange, Insert, etc) 您需要更新向列表添加/更新项的其他方法(索引setter,AddRange,Insert等)
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