Optional Parameters in Abstract method? Is it possible?

Question

I have a abstract base class.

I have 2 derived classes from this base class.

Is there anyway that one of my classes can ignore the string parameter in the abstract overide usage? Or do I have to just send in a blank one and ignore it? (making readability drop slightly)

Can I have one function that has some sort of optional parameter so that both of the following derived classes would compile?

PS - The following code is riddled with in-compilable code for the example of what I would like to do

PS PS - Yes i have compiled the following code already - see above comment for outcome

public abstract class MyBaseClass
{                                            //optional string?
    public abstract void FunctionCall(int i, string s = "");
}

public class MyDerivedClass : MyBaseClass
{
    public override void FunctionCall(int i)
    {
        MessageBox.Show(i.ToString());
    }
}

public class YourDerivedClass : MyBaseClass
{
    public override void FunctionCall(int i, string s)
    {
        MessageBox.Show(s + " " + i.ToString());
    }
}

Answer 1

If you don't absolutely need FunctionCall to be abstract, you can declare two versions of it:

public abstract class MyBaseClass
{
    public virtual void FunctionCall(int i)
    {
        this.FunctionCall(i, "");
    }
    public virtual void FunctionCall(int i, string s)
    {

    }
}

public class MyDerivedClass : MyBaseClass
{
    public override void FunctionCall(int i)
    {
        MessageBox.Show(i.ToString());
    }
}

public class YourDerivedClass : MyBaseClass
{
    public override void FunctionCall(int i, string s)
    {
        MessageBox.Show(s + " " + i.ToString());
    }
}

Otherwise, if it must be abstract to ensure it is implemented, you could still add two versions, it just makes the inheritors more verbose:

public abstract class MyBaseClass
{
    public abstract void FunctionCall(int i);
    public abstract void FunctionCall(int i, string s);
}

public class MyDerivedClass : MyBaseClass
{
    public override void FunctionCall(int i, string s)
    {
        throw new NotImplementedException();
    }
    public override void FunctionCall(int i)
    {
        MessageBox.Show(i.ToString());
    }
}

public class YourDerivedClass : MyBaseClass
{
    public override void FunctionCall(int i)
    {
        throw new NotImplementedException();
    }
    public override void FunctionCall(int i, string s)
    {
        MessageBox.Show(s + " " + i.ToString());
    }
}