Send MDI Controls to Back and Front

Sir, I am doing a Windows Application program.

I have a MDi Form and three other forms.

all three forms are accessing form MDi Form.

here is the MDi form:-




I do the function to send the control backward when a form being open.

here is the code to send them back:-

if (MdiChildren != null)
            {
                btnaddProduct.SendToBack();
                btnpurchaseDetails.SendToBack();
                btnRegister.SendToBack();

            }

Like this I want to bring them toFront when I close the opened form.


here is the form look after I close a form:-



I want your help to bring those three buttons to Front .please send me code to function this.