-------------------------------------------------Animal.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication2
{
public class Animal
{
}
}
-------------------------------------------------Dog.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication2
{
public class Dog:Animal
{
}
}
-------------------------------------------------IOut.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication2
{
public interface IOut<out T>//协变
{
T Xb();//T 只能作为返回值
}
}
-------------------------------------------------IIn.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication2
{
public interface IIn<in T>//抗变
{
void Kb(T t);//T 只能作为参数
}
}
-------------------------------------------------ListOutIn.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication2
{
public class ListOutIn<T> : IOut<T>, IIn<T>
{
public T Xb()
{
throw new NotImplementedException();
}
public void Kb(T t)
{
throw new NotImplementedException();
}
}
}
-------------------------------------------------主程序
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication2
{
class Program
{
static void Main(string[] args)
{
//out --> 协变--> 输出--> 隐式转换
//in --> 抗变--> 输入--> 显示转换
//协变
IOut<Animal> oa = new ListOutIn<Animal>();
IOut<Dog> od = new ListOutIn<Dog>();
oa = od;//因为接口是协变的,隐式转换成功
//抗变
IIn<Animal> ia = new ListOutIn<Animal>();
IIn<Dog> id = new ListOutIn<Dog>();
id = ia;//因为接口是抗变的,显示转换成功
}
}
}
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