本文介绍了使用更多指定的返回类型(协方差)覆盖抽象属性的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
class Base {}
abstract class A
{
abstract public List<Base> Items { get; set; }
}
class Derived : Base {}
class B : A
{
private List<Derived> items;
public override List<Derived> Items
{
get
{
return items;
}
set
{
items = value;
}
}
}
编译器说B.Items必须是匹配匹配的重写成员" A.Items的基本元素列表.我该怎么做?
解决方案
最初尝试完成的工作是不可能的-.属性也是一样,因为属性只是这对方法. /p>
但是您可以使您的类通用:
class Base {}
abstract class A<T>
where T : Base
{
abstract public List<T> Items { get; set; }
}
class Derived : Base {}
class B : A<Derived>
{
private List<Derived> items;
public override List<Derived> Items
{
get
{
return items;
}
set
{
items = value;
}
}
}
class Base {}
abstract class A
{
abstract public List<Base> Items { get; set; }
}
class Derived : Base {}
class B : A
{
private List<Derived> items;
public override List<Derived> Items
{
get
{
return items;
}
set
{
items = value;
}
}
}
The compiler says that B.Items must be List of Base elements "to match overridden member" A.Items. How can i make that work?
解决方案
What you've tried to accomplish initially is impossible - .NET does not support co(contra)variance for method overload. The same goes for properties, because properties are just the pair of methods.
But you can make your classes generic:
class Base {}
abstract class A<T>
where T : Base
{
abstract public List<T> Items { get; set; }
}
class Derived : Base {}
class B : A<Derived>
{
private List<Derived> items;
public override List<Derived> Items
{
get
{
return items;
}
set
{
items = value;
}
}
}
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