将List <Base>与List <Derived>组合在一起

Question

我怎样才能做到这一点:

public class BaseItem
{
    public string Title { get; set; }
}

public class DerivedItem : BaseItem
{
    public string Description { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        List<BaseItem> baseList = new List<BaseItem>();
        List<DerivedItem> derivedList = new List<DerivedItem>();
        baseList.Add(new BaseItem() { Title = "tester"});
        derivedList.Add(new DerivedItem() { Title = "derivedTester", Description = "The Description" });

        baseList.AddRange(derivedList);
    }
}

谢谢,亨克

Answer 1

在C#3.0/.NET 3.5中,IEnumerable<T>不是协变的.但是,这可能在C#4.0/.NET 4.0中正常工作.

现在,您可以(在.NET 3.5中)使用:

baseList.AddRange(derivedList.Cast<BaseItem>());

(注意你需要" using System.Linq;"在文件的顶部)

在此之前...可能最容易循环:

foreach(BaseItem item in derivedList) {baseList.Add(item);}