摘要class投射问题

Question

我有这个代码：

public abstract class Animal
{
    public string Name { get; set; }
}

public class Dog : Animal
{
    [JsonProperty("name")]
    public new string Name { get; set; }
}

public static void Main()
{
    var dog = new Dog
    {
        Name = "Spark"
    };

    Console.WriteLine(dog.Name);
    Console.WriteLine(((Animal)dog).Name == null);
}

将输出：

Spark
True

为什么 Name 属性 null 转换为 Animal 时？

如果我想将我的对象转换为 Animal，如何修复它？如何保留属性值？

Answer 1

你所期望的是由override实现的，所以你必须重写属性:

public override string Name { get; set; }

但是为了做到这一点，你需要将属性标记为 abstract，否则你会得到一个错误：

error CS0506: 'Dog.Name': cannot override inherited member 'Animal.Name' because it is not marked virtual, abstract, or override

Refer to this post. 在那里你可以阅读：

The override modifier may be used on virtual methods and must be used on abstract methods. This indicates for the compiler to use the last defined implementation of a method. Even if the method is called on a reference to the base class it will use the implementation overriding it.

Answer 2

public class Dog : Animal
{
     string name = null;
     public new string Name { get { return name; } set { name = value; base.Name = name; } } }
}

摘要class投射问题

Abstract class cast issue

c#

abstract-class