接口继承_1

摘自Jeffrey的CLR via CSharp

接口方法默认是virtual and sealed. 意思是接口方法默认是没有继承的,这一点在你需要多态时需要注意。

Base b = new Base();  
Derived d = new Derived();  
b = new Derived();  
// Calls Dispose by using b's type: "Base's Dispose"  
b.Dispose();  
((IDisposable)b).Dispose();//通过把b转化为接口可以实现调用子类方法

由于没有多态，上述Dispose调用的基类的方法。

源码如下：

class Program
    {
        static void Main(string[] args)
        {
            /************************* First Example *************************/
            Base b = new Base();
            // Calls Dispose by using b's type: "Base's Dispose"
            //b.Dispose();
            // Calls Dispose by using b's object's type: "Base's Dispose"
            //((IDisposable)b).Dispose();
            /************************* Second Example ************************/
            Derived d = new Derived();
            // Calls Dispose by using d's type: "Derived's Dispose"
            //d.Dispose();
            // Calls Dispose by using d's object's type: "Derived's Dispose"

            //((IDisposable)d).Dispose();
            /************************* Third Example *************************/
            b = new Derived();
            // Calls Dispose by using b's type: "Base's Dispose"
            b.Dispose();
            // Calls Dispose by using b's object's type: "Derived's Dispose"
            ((IDisposable)b).Dispose();

        }
    }
    // This class is derived from Object and it implements IDisposable
    internal class Base : IDisposable
    {
        // This method is implicitly sealed and cannot be overridden
        public void Dispose()
        {
            Console.WriteLine("Base's Dispose");
        }
    }
    // This class is derived from Base and it re-implements IDisposable
    internal class Derived : Base, IDisposable
    {
        // This method cannot override Base's Dispose. 'new' is used to indicate
        // that this method re-implements IDisposable's Dispose method
        new public void Dispose()
        {
            Console.WriteLine("Derived's Dispose");
            // NOTE: The next line shows how to call a base class's implementation (if desired)
            // base.Dispose();
        }
    }

如果接口方法需要多态，源码可以改成如下：

internal class Base : IDisposable
    {
        // This method is implicitly sealed and cannot be overridden
        public virtual void Dispose()
        {
            Console.WriteLine("Base's Dispose");
        }
    }
    // This class is derived from Base and it re-implements IDisposable
    internal class Derived : Base, IDisposable
    {
        // This method cannot override Base's Dispose. 'new' is used to indicate
        // that this method re-implements IDisposable's Dispose method
        public override void Dispose()
        {
            Console.WriteLine("Derived's Dispose");
            // NOTE: The next line shows how to call a base class's implementation (if desired)
            // base.Dispose();
        }
    }