从C＃中的子类访问父方法

Question

I am trying to make an equivalent code in C# for a piece of code that I already have in Java. The Java code is as follows.

class Test
{
        public static void main (String args[])
        {
            C1 o1 = new C1();
            C2 o2 = new C2();
            System.out.println(o1.m1() + " " + o1.m2() + " " + o2.m1() + " " + o2.m2());
        }

}

class C1 
{
    void C1() {}
    int m1() { return 1; }
    int m2() { return m1(); }
}

class C2 extends C1
{
    void C2() {}
    int m1() { return 2; }
}

This gives the output 1 1 2 2. Now, I have written this code for C#.

class Program
    {
        static void Main(string[] args)
        {
            C1 o1 = new C1();
            C2 o2 = new C2();
            Console.WriteLine(o1.M1()+ " "+ o1.M2()+ " "+ o2.M1()+ " "+ ((C2)o2).M2()+ "\n");
            Console.ReadKey();
        }
    }

    public class C1
    {
        public C1()
        {
        }
        public int M1()
        {
            return 1;
        }
        public int M2()
        {
            return M1();

        }
    }

    public class C2:C1
    {
        public C2()
        {             
        }
        public int M1()
        {
            return 2;
        }
    }

This, however, prints 1 1 2 1 as the inherited M2 in C2 calls the M1 in C1 and not the M1 in C2. How can I make it call M1 in C2 with minor modifications?

Answer 1

Note: in C# you need to use virtual and override keywords to allow overriding. MSDN :

The virtual keyword is used to modify a method, property, indexer, or event declaration and allow for it to be overridden in a derived class .

(my bolding)

 class Program
    {
        static void Main(string[] args)
        {
            C1 o1 = new C1();
            C2 o2 = new C2();
            Console.WriteLine(o1.M1() + " " + o1.M2() + " " + o2.M1() + " " + ((C2)o2).M2() + "\n");
            Console.ReadKey();
        }
    }

    public class C1
    {
        public C1()
        {
        }
        public virtual int M1()
        {
            return 1;
        }
        public  int M2()
        {
            return M1();

        }
    }

    public class C2 : C1
    {
        public C2()
        {
        }
        public override int M1()
        {
            return 2;
        }
    }