c# - 如何在 C# 中将 X 列表转换为 Y 列表？

Question

我有两个基类 FirstBase 和 SecondBase。我也有 2 个类派生自它们，DerivedFirst 和 DerivedSecode，它们都具有几乎相同的属性。源代码如下。

public abstract class FirstBase
{
    //some method
}

public abstract class SecondBase
{
    //some method
}

public class DerivedFirst : FirstBase
{
    //override methods of its parent

    public static implicit operator DerivedFirst(DerivedSecond second)
    {
        //doing some logic here
    }
}

public class DerivedSecond : SecondBase
{
    //override methods of its parent

    public static implicit operator DerivedSecond(DerivedFirst first)
    {
        //doing some logic here
    }
}

从这段代码中，我可以毫无问题地创建 DerivedFirst 的实例并分配给 DerivedSecond。但是，当我尝试像下面的代码那样转换它们的列表时，它没有结果。

List<DerivedFirst> firstList;
List<DerivedSecond> secondList;

//doing some operation here

List<DerivedSecod> test = firstList.Cast<DerivedSecond>(); // don't have any output here.

如何将 firstList 转换为 List()？

Answer 1

用户定义的隐式转换仅在编译时被考虑，而不是在运行时(source)。您可以改用 Select:

List<DerivedSecond> foo = firstList.Select(x => (DerivedSecond)x).ToList();