Question

I was just trying to master the concept of virtual function using a console app. I noticed as soon as I override a base class function, return baseclassname.functionname(parameters) gets inserted in my function body automatically. Why does this happen?

class advanc
{
    public virtual int  calc (int a , int b)
    {        
         return (a * b);        
    }        
}

class advn : advanc
{
     public override int calc(int a, int b)
     {
          //automatically inserted
          return base.calc(a, b);
      }        
}

Answer 1

By overriding a virtual function you expand the functionality of your base class and then call the base class for the ‘base functionality’.

If you would remove the ‘return base.calc(a,b)‘ line, the base class code would not execute.

If you want to completely replace the functionality this is not a problem but if you want to extend the functionality then you should also call the base class.

The following code demonstrates this (just put it in a Console Application)

class advanc
{
    public virtual int calc(int a, int b)
    {
        Console.WriteLine("Base function called");
        return (a * b);
    }
}

class advn : advanc
{
    public bool CallBase { get; set; }
    public override int calc(int a, int b)
    {
        Console.WriteLine("Override function called");

        if (CallBase)
        {
            return base.calc(a, b);
        }
        else
        {
            return a / b;
        }
    }
}

private static void Main()
{
    advn a = new advn();

    a.CallBase = true;
    int result = a.calc(10, 2);
    Console.WriteLine(result);

    a.CallBase = false;
    result = a.calc(10, 2);
    Console.WriteLine(result);
    Console.WriteLine("Ready");
    Console.ReadKey();
}