Remove margin view in scrollview

Question

I have a scrollview that will add custom views to add some information. However when I add the view in scrollview he gets a margin on the left and at the top, even though I set the axis x and y the margin continues, see in the image. ps:I'm using Xamarin, know more objective c / cocoa

add view

    private NSView viewToBeAdded(float x,float y) 
    {
        NSBox nbox =  new NSBox (new RectangleF (x,y, BOX_WIDTH, BOX_HEIGHT))
        {
            BoxType = NSBoxType.NSBoxCustom,
            BorderType = NSBorderType.NoBorder,
            TitlePosition = NSTitlePosition.NoTitle,
            FillColor = NSColor.White,
            Shadow = new NSShadow () { ShadowColor = NSColor.LightGray, ShadowOffset = new System.Drawing.SizeF (1, -1.5f), ShadowBlurRadius = 1.0f},
        };
        nbox.AddSubview (Imagem());
        return nbox;
    }