Difference between virtual and abstract methods [duplicate]

Answer 1

an abstract method must be call override in derived class other wise it will give compile-time error and in virtual you may or may not override it's depend if it's good enough use it

Example:

abstract class twodshape
{
    public abstract void area(); // no body in base class
}

class twodshape2 : twodshape
{
    public virtual double area()
    {
        Console.WriteLine("AREA() may be or may not be override");
    }
}