C# - Polymorphism of classes inside array

Question

I am trying to utlise polymorphism for class instances inside an Object array:

ClassA a = new ClassA();
ClassB b = new ClassB();

Object[] classes = new Object[] { a, b };

An example of one of the classes would be:

public class ClassA 
{
    public string PrintOutput()
    {
        return "254,62,455,5,15,62,656";
    }
}

I've tried something similar to: C# class polymorphism

The issue this person had was that they created an array of type A (one of the classes). Changing the array type to Object leads to the error: object not containing a definition for the method/no accessible extension method accepting a first argument of type object could be found.

EDIT: At the moment, I'm just trying to print the outputs from the method in each class:

foreach (Object obj in classes)
{
    Console.WriteLine(obj.PrintOutput());
}

obj.PrintOutput() is where I get the above error.

Did you consider using and interface that all your classes would implement? — cmos
– cmos, Commented Jan 14, 2021 at 14:56
What is the problem? Are you trying to enumerate the classes and call method or what? Can you show the code which doesn't work and the error you get? — Sinatr
– Sinatr, Commented Jan 14, 2021 at 14:58
@Sinatr Edited the question to show where I get the error. Basically just trying to enumerate the classes at the moment. — Kevin Niland
– Kevin Niland, Commented Jan 14, 2021 at 15:02

Lana · Accepted Answer · 2021-01-14 15:02:29Z

6

One way is using common interface

public interface IPrintOutput
{
    string PrintOutput();
}

public class ClassA : IPrintOutput
{
    public string PrintOutput()
    {
         return "254,62,455,5,15,62,656";
    }
}

public class ClassB : IPrintOutput
{
    public string PrintOutput()
    {
         return "something else";
    }
}

IPrintOutput[] classes = new IPrintOutput[] { a, b };

Second way you can override ToString and use it (every object has ToString)

answered Jan 14, 2021 at 15:02

Lana

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Comments

alex-dl · Accepted Answer · 2021-01-14 15:05:47Z

2

A common interface is the best solution. Another solution is define classes as dynamic:

 dynamic[] classes = new Object[] { a, b };

answered Jan 14, 2021 at 15:05

alex-dl

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