Call derived class constructor before base class

Question

I need to execute derived class constructor before base class constructor. I am attaching code which is using virtual object in base class which need to be initialised in derived class. We decide type of virtual object in derived class and then assign values to that object once we have type of that object. How could I call derived class constructor before base class constructor in this scenario.

public class BaseClass : UserControl, INotifyPropertyChanged
{
    public Path ConnIn;
    public Path ConnOut;

    public virtual ObjectBase BaseObject { get; set; }

    public void BaseClass(XmlElementConfig config)
    {
        this.BaseObject.Title = config.Title;
        this.BaseObject.GroupID = config.GroupID;
    }
}

public partial class DerivedClass : CanvasBase
{
    private Audio_MonitorAction audio_objectAction;

    public override ObjectBase BaseObject
    {
        get { return audio_objectAction; }
        set
        {
            audio_objectAction = (Audio_MonitorAction)value;
            NotifyPropertyChanged();
        }
    }

    public DerivedClass(XmlElementConfig config) : base(config)
    {
        InitializeComponent();
        audio_objectAction = new Audio_MonitorAction(createGuid);
    }
}

Possible duplicate of How to call constructor inside the class? — Rekshino
I am having the same problem. How are you supposed to use virtual methods in a base constructor, why was this crap error implemented anyways. You don't need to call the base constructor first in C++, why do you need to do it a very loosely coupled language like javascript. — Nick Sotiros

ASh ASh · Accepted Answer · 2018-03-14T08:23:26

"execute derived class constructor before base class constructor" is impossible

if possible, move initialization into BaseObject property (why should it be virtual?)

public class BaseClass : UserControl, INotifyPropertyChanged
{
    public Path ConnIn;
    public Path ConnOut;

    private ObjectBase baseObject;
    public ObjectBase BaseObject
    {
        get { return baseObject; }
        set
        {
            baseObject = value;
            if (baseObject != null)
            {
                baseObject.Title = config.Title;
                baseObject.GroupID = config.GroupID;
            }
            NotifyPropertyChanged();
        }
    }

    XmlElementConfig config;
    public void BaseClass(XmlElementConfig config)
    {
        this.config = config;
    }
}

public partial class DerivedClass : CanvasBase
{
    private Audio_MonitorAction audio_objectAction;

    public DerivedClass(XmlElementConfig config) : base(config)
    {
        InitializeComponent();
        BaseObject = audio_objectAction = new Audio_MonitorAction(createGuid);
    }
}

Call derived class constructor before base class

2 Answers