Creating object of a class with parameterised constructors c#

Question

I have a class with multiple parameterised constructors.

class MyClass{
    public MyClass(Context context) : this(context, VERTICAL)
    {
    }
    public MyClass(Context context, int Orientation) : base(context)
    {
        init(context, Orientation);
    }

    public MyClass(Context context, Android.Util.IAttributeSet attrs, int defStyle) : base(context, attrs, defStyle)
    {
              //more code
    }

    // I have to make an object of this MyClass into MyDataSetObserver class.

    public class MyDataSetObserver : DataSetObserver
    {
        MyClass mc;

        public MyDataSetObserver(MyClass _mc)
        {
            mc= _mc;
        }

        public override void OnChanged()
        {
                mc.onDataChanged ();
        }

            public override void OnInvalidated()
        {
                mc.onDataChanged();
        }
    }

//DatasetObserver usage

    public void setAdapter(Android.Widget.IAdapter myadapter, int initialPosition)
    {
        if (this.adapter != null) 
        {
            this.adapter.UnregisterDataSetObserver (adapterDataObserver);
        }

        //Assert.assertNotNull ("adapter should not be null", adapter);

        this.adapter = myadapter;
        adapterDataCount = adapter.Count;
        adapterDataObserver = new MyDataSetObserver (this);
        this.adapter.RegisterDataSetObserver (adapterDataObserver);
        if (adapterDataCount > 0) {
            SetSelection (initialPosition);
        }
    }
}

but this gives me the value of mc as null..

Also, I need to do a constructor chaining, Is this the right approach?

Where are you seeing mc is null? In the MyDataSetObserver constructor? — StevieB
– StevieB, Commented Dec 23, 2013 at 6:38
@StevieB yes, mc is null in the MyDataSetObserver constructor — user3034944
– user3034944, Commented Dec 23, 2013 at 6:41
I would expect mc to be non null in the MyDataSetObserver constructor with the posted code after the assignment statement. The 'this' being passed in must be valid so _mc will be valid and hence mc must be valid. — StevieB
– StevieB, Commented Dec 23, 2013 at 7:06
I don't suppose you've mixed up mc and _mc in your code? The usual style is to prefix private members with an underscore and prefix locals with a letter whereas the opposite style is being used in the constructor. — StevieB
– StevieB, Commented Dec 23, 2013 at 7:08

Gokul E · Accepted Answer · 2013-12-23 06:33:36Z

1

adapterDataObserver = new MyDataSetObserver (this);

What is this Here? is your class is the Instance of MyClass ? then It should have a Context Object.

or else just Create the Instance of MyClass by the answer of @Yohannes and then Construct the MyDataSetObserver object passing this

answered Dec 23, 2013 at 6:33

Gokul E

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