Expose class attributes with accessor

Question

I don't know the correct technical terms to describe my question, so I'll give an example:

    private Point _PrivateVect = new Point();
    public Point Publicvect
    {
        get
        {
            return _PrivateVect;
        }
        set
        {
            _PrivateVect = value;
        }
    }

The problem is that if I wanted to access Publicvect.X I get the error Cannot modify the return value of 'Publicvect' because it is not a variable. Is there a way around this? Or do I just need to do Publicvect = new Point(NewX, Publicvect.Y); forever?

Answer 1

Yet another reason that mutable structs are evil. One workaround is to expose the dimensions as accessors for convenience:

public Point PublicX {
    get {return _PrivateVect.X;}
    set {_PrivateVect.X = value;}
}
public Point PublicY {
    get {return _PrivateVect.Y;}
    set {_PrivateVect.Y = value;}
}

But other that this; yes you would need to do the new Point(x,y) each time, since Point is a struct. When you access it via a property you get a copy of it, so if you mutate the copy and then discard the copy, you simply lose the change.

Answer 2

The problem you have here is that the Point type is a Value Type. So when you manipulate Pointvect.X you are really manipulating a temporary copy of the value type, which of course has no effect on the original instance.