具有通用基类的派生类的集合 [英] Collection of derived classes that have generic base class

问题描述

说我有几个派生类的基类是一个通用类。每个派生类继承具有特定类型覆盖的基类（但是所有类型也都派生自单个基本类型）。

例如：

我有一个基本行类

  class RowBase 
 {
 //一些属性和抽象方法
} 
  

派生自行基类

  class SpecificRow1：RowBase 
 {
 //一些额外的属性和覆盖
} 
 
 class SpecificRow2：RowBase 
 {
 //一些额外的属性和覆盖
} 
  

然后我有一个第二个基类是一个泛型类，它包含一个来自RowBase派生类的集合

  class SomeBase< T>其中T：RowBase 
 {
 ICollection< T> Collection {get;组; } 
 //其他一些属性和抽象方法
} 
  

从SomeBase派生但是使用不同的特定行类的两个类

  class SomeClass1：SomeBase< SpecificRow1& 
 {
 //一些属性和覆盖
} 
 
 class SomeClass2：SomeBase< SpecificRow2> 
 {
 //一些属性和覆盖
} 
  

在我的主要或更大的范围，我想创建一个包括SomeClass1和SomeClass2对象的列表/集合。喜欢

  ICollection< CombinedCollection = new ... 
 CombinedCollection.Add（new SomeClass1（））
 CombinedCollection.Add（new SomeClass2（））
。 
。 
。 
 //添加更多对象并对集合
做一些事情。 
。 
。 
  

问题是：有可能有这样的收集吗？如果可能，我该如何实现呢？如果没有，什么可以替代方法？

解决方案

这可以通过协变和对照。

添加一个新接口，并使T参数协变（使用 out 关键字）：

  interface ISomeRow< out T>其中T：RowBase 
 {
} 
  

SomeBase应该继承该接口：

  class SomeBase< T> ：ISomeRow< T>其中T：RowBase 
 {
 //一些其他属性和抽象方法
} 
  

然后，以下将工作：

  List< ISomeRow< RowBase> myList = new List< ISomeRow< RowBase>>（）; 
 myList.Add（new SomeClass1（））; 
 myList.Add（new SomeClass2（））;希望这是您要查找的内容：）
 
 
Say I have several derived classes whose base class is a generic class. Each derived class inherit the base class with a specific type override(but all types are also derived from a single base type).

For example:

I have a base row class
class RowBase
{
    //some properties and abstract methods
}
And I have two specific row classes that are derived from the row base class
class SpecificRow1 : RowBase
{
    //some extra properties and overrides
}

class SpecificRow2 : RowBase
{
    //some extra properties and overrides
}
Then I have a second base class that is a generic class which contains a collection of derived classes from RowBase
class SomeBase<T> where T : RowBase
{
    ICollection<T> Collection { get; set; }
    //some other properties and abstract methods
}
Then I have two classes that derive from SomeBase but are using different specific row class
class SomeClass1 : SomeBase<SpecificRow1>
{
     //some properties and overrides
}

class SomeClass2 : SomeBase<SpecificRow2>
{
     //some properties and overrides
}
Now that in my main or a bigger scope, I want to create a list/collection that consist both SomeClass1 and SomeClass2 objects. Like
ICollection<???> CombinedCollection = new ...
CombinedCollection.Add(new SomeClass1())
CombinedCollection.Add(new SomeClass2())
.
.
.
//add more objects and do something about the collection
.
.
.
The question is: is it possible to have such collection? If it is possible, how can I achieve this? If no, what can be an alternative way?
解决方案
This can be done with the help of Covariance and Contravariance.

Add a new interface that and make the T parameter covariant (using the out keyword):
interface ISomeRow<out T> where T : RowBase
{
}
SomeBase should inherit that interface like this:
class SomeBase<T> : ISomeRow<T> where T : RowBase
{
    //some other properties and abstract methods
}
Then, the following will work:
List<ISomeRow<RowBase>> myList = new List<ISomeRow<RowBase>>();
myList.Add(new SomeClass1());
myList.Add(new SomeClass2());
Hope this is what you're looking for :)

                        
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