C# .NET extension without extension method [closed]

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I have a base class and multiple derived classes:

public class Camera
{
}

public class CameraManufacturerA : Camera
{
}

public class CameraManufacturerB : Camera
{
}

public class CameraManufacturerC : Camera
{
}

Now I want to add features that extend the base functionality:

public class CameraFeatureA : Camera
{
    public int FeatureProperty { get; set; }

    public bool RunFeatureA();
}

These features only make sense for certain child classes, I aim for something like this:

public class MyCamera : CameraManufacturerA, CameraFeatureB, CameraFeatureD
{
}

I know, exactly like this, it won't be possible (for good reasons). I spent a lot of time trying to find something similar, but could not find a solution that comes close. Any Ideas?

One more info: the combined class (MyCamera) will be used in a kind of code editor that uses reflection. That is why it is important that properties of the child classes are indeed properties. But I could work with a "hacky" solution using reflection or dynamic class creation. I only need the final combined class at runtime.

C# doesn't support multiple inheritance of classes. Except it allows inheritance of multiple interfaces. I think you need to revise the purpose of creating multiple classes for CameraManufacturerA, CameraFeatureB, CameraFeatureD (Probably typo? Should be CameraManufacturerB, CameraManufacturerC?). Without actual context, we can't know what you are trying to achieve. — Yong Shun
– Yong Shun, Commented Oct 30 at 8:49
class MyCamera { CameraFeatureA a; CameraFeatureB b; CameraFeatureC c; } If you need a combined class, why do you need inheritance? — shingo
– shingo, Commented Oct 30 at 8:53
Because the class is used via reflection. I.e it is bound to a view that lists all its properties. At this point it would be nice when all properties of the Features would be properties of the combined class. — Moj
– Moj, Commented Oct 30 at 9:04
It sounds like basically you should redesign this. A camera feature isn't a camera, so I'm not sure why it would derive from the Camera class. I suspect it would be better to have a CameraFeature class (or possibly an ICameraFeature interface) and then make Camera have a list of CameraFeatures for features that camera supports. — Jon Skeet
– Jon Skeet, Commented Oct 30 at 9:07

JonasH · Accepted Answer · 2025-10-30 09:52:40Z

If the goal is some kind of dynamic or reflection based feature you might want to design your type model to separate out the features into separate types, composition over inheritance. This could look something like:

public abstract class Camera
{
    public abstract IEnumerable<ICameraFeature> AllFeatures { get; }
}
public class CameraManufacturerA : Camera
{
    public FeatureA FeatureA { get; } = new FeatureA();
    public override IEnumerable<ICameraFeature> AllFeatures => [FeatureA];
}

public interface ICameraFeature
{
    public void Run();
}

public class FeatureA : ICameraFeature
{
    public int FeatureProperty { get; set; }
    public void Run() { }
}

Your editor can simply iterate over all features and display the necessary controls. There will be some repetition for each manufacturer, but that is unavoidable if each manufacturer has unique but overlapping feature sets. You could also use the visitor pattern to help map features to corresponding UI controls if you want to avoid reflection or type checks.

An alternative would be to use additional base classes, but this will only really work if the feature sets follow a strict hierarchy, something like :

public class CameraWithFeatureA : Camera { 
   public int FeatureProperty { get; set; }
   public bool RunFeatureA();
}
public class CameraManufacturerA : CameraWithFeatureA {}
public class CameraManufacturerB : CameraWithFeatureA {}
public class CameraManufacturerC : Camera{}

It is also possible to mix and match patterns. If say 90% of all cameras have features A, B and C you might add a base class that includes these, and handle the remaining 10% separately.

You can also use interfaces to describe each feature, since a class can implement however many interfaces it wants:

public interface ICameraFeatureA
{
    public int FeaturePropertyA { get; set; }
    public void RunA() { }
}
public interface ICameraFeatureB
{
    public double FeaturePropertyB { get; set; }
    public void RunB() { }
}
public class CameraWithFeatureA : ICameraFeatureA, ICameraFeatureB{ 
   ...
}

In some cases you may need to use explicit interface implementations if multiple features use the same method or property names:

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