insert View into RelativeLayout's childerne Xamarin Forms

Question

I'm in need of inserting a view obj to the children array of a relativeLayout. but the problem is that i don't know how i can do it so it's Relative To Parent. like i do when i added it, like shown below

layout.Children.Add(BoxView, Constraint.RelativeToParent((parent) => {
                    return parent.Width / 10;
                }), Constraint.RelativeToParent((parent) => {
                    return parent.Height / 5;
                }), Constraint.RelativeToParent((parent) => {
                    return parent.Width - 2 * (parent.Width / 10);
                }), Constraint.RelativeToParent((parent) => {
                    return parent.Height / 2;
                }));

Do anyone know how this can be done?

as always, Thanks for your time.