Inherit from a non-abstract class

Question

I have several classes which inherit from a BaseClass which has an abstract method called GetData. In one of them I want to basically inherit from again and provide use a new method called GetArticles which I call from GetData. Here's the code.

public abstract class BaseClass
{
    internal abstract void GetData();
}

internal class FirstClass : BaseClass
{
    internal override void GetData()
    {
        // calls GetArticles
    }

    protected void GetArticles()
    {
    }
}

internal class SecondClass : FirstClass
{
    protected new void GetArticles()
    {
    }
}

GetArticles is never called in SecondClass . It calls the one in FirstClass , even though my object is of type SecondClass . I can't make GetArticles in FirstClass Abstract because I want to use FirstClass in its own right.

Any suggestions?

Answer 1

Your method has to marked as virtual in FirstClass and overriden using override keyword in SecondClass .

internal class FirstClass : BaseClass
{
    internal override void GetData()
    {
        // calls GetArticles
    }

    protected virtual void GetArticles()
    {
    }
}

internal class SecondClass : FirstClass
{
    protected override void GetArticles()
    {
    }
}

new modifier hides the underlying virtual method, which is not what you want. Check Knowing When to Use Override and New Keywords (C# Programming Guide) on MSDN.

Answer 2

Declare GetArticles in your FirstClass as virtual. In the second class remove new and add override

Answer 3

Make GetArticles virtual.

protected virtual void GetArticles()
{
}

Answer 4

Normal Class can not contain abstract method.Whereas abstract class can contain normal method. If a normal class inherit abstract class and hold any abstract method than must be override due to inheritance in derived class.