如何将基本类型的列表转换为派生类型的列表 [英] How to cast a list of a base type to list of the derived type

问题描述

从派生类到基类，似乎有许多问题反过来，但我的问题是如何将基类型列表转换为派生类型列表?

There seems to be a number of questions going the other way, from a derived class to a base class but my issue is how to cast a list of a base type to list of the derived type?

public class MyBase {
    public int A;
}

public class MyDerived : MyBase {
    public int B;
}

public void MyMethod() {
    List<MyBase> baseCollection = GetBaseCollection();
    List<MyDerived> derivedCollection = (List<MyDerived>)baseCollection; // Which doesn't work
}

我最终得出的解决方案不是很好.

Solution I ended up with which is not very elegant.

public class MyBase {
    public int A;
}

public class MyDerived {
    public int B;
    public MyBase BASE;
}
public void MyMethod() {
    List<MyBase> baseCollection = GetBaseCollection();
    List<MyDerived> derivedCollection = new List<MyDerived>();
    baseCollection.ForEach(x=>{
        derivedCollection.Add(new derivedCollection(){ BASE = x});
    });
}

一定有更好的方法...

There must be a better way...

推荐答案

您可以使用Linq方法 OfType< MyDerived>()，例如:

You can use Linq method OfType<MyDerived>(), e.g.:

List<MyDerived> derivedCollection = baseCollection.OfType<MyDerived>().ToList();

它将删除所有不是 MyDerived 类的项目

It will remove all the items which are not MyDerived class though

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