在c#中实例化泛型类

Question

在下面的代码中,输出是;

厄尼伯特埃尔莫

为什么最后的输出是Elmo？不应该是厄尼吗？因为我实例化dog.Creature对象new Cat();.我认为,Name财产Cat类覆盖Name财产Creature类.

class Class1
{
    public static void Main(string[] args)
    {
        var dog = new Dog();
        var cat = new Cat();
        dog.Creature = new Cat();

        Console.WriteLine(cat.Name); //outputs Ernie
        Console.WriteLine(dog.Name); //outputs Bert 
        Console.WriteLine(dog.Creature.Name); //outputs Elmo, why not Ernie?
        Console.Read();
    }
}
public class Animal<T> where T : Creature
{
    public T Creature { get; set; }
    private string _name = "Oscar";
    public string Name { get { return _name; } set { _name = value; } }
}
public class Creature
{
    private string _name = "Elmo";
    public string Name { get { return _name; } set { _name = value; } }
}
public class Cat : Creature
{
    private string _name = "Ernie";
    public string Name { get { return _name; } set { _name = value; } }
}
public class Dog : Animal<Creature>
{
    private string _name = "Bert";
    public string Name { get { return _name; } set { _name = value; } }
}

Answer 1

首先,这与泛型无关.如果你写下你会得到完全相同的行为:

Creature cat = new Cat();
Console.WriteLine(cat.Name);

不要忘记编译时类型Dog.Creature是Creature.

我认为Cat类的Name属性会覆盖Creature类的Name属性.

不,因为它不是虚拟财产而您还没有使用过override.您应该有一个编译时警告,明确表示您正在隐藏该成员,而不是覆盖它:

Test.cs(30,19): warning CS0108: 'Cat.Name' hides inherited member
        'Creature.Name'. Use the new keyword if hiding was intended.

如果你改变Cat并且Creature像这样,它将起作用:

public class Creature
{
    private string _name = "Elmo";
    public virtual string Name { get { return _name; } set { _name = value; } }
}

public class Cat : Creature
{
    private string _name = "Ernie";
    public override string Name { get { return _name; } set { _name = value; } }
}

......但我个人试图避免这种情况.为什么不直接使用setter Creature？你为什么要_name在Cat对象中有两个字段？这不是说它们意味着服务于不同的目的,是吗？

目前还不清楚你想要实现什么,但我几乎肯定会给这个Creature类一个构造函数,并将该名称作为参数.如果可能的话,我可能会将该属性设为只读.