Dragging picturebox , hides behind panel

[invader7]

Hello , i want drag and drop to my form , i have some pictureboxes and i want to drag them over the form.

        private bool isDragging = false;
        private int currentX, currentY;

        private void brown_pictureBox_MouseDown(object sender, MouseEventArgs e)
        {
            isDragging = true;

            currentX = e.X;
            currentY = e.Y;

            brown_pictureBox.BringToFront();
        }

        private void brown_pictureBox_MouseMove(object sender, MouseEventArgs e)
        {
            if (isDragging)
            {
                brown_pictureBox.Top = brown_pictureBox.Top + (e.Y - currentY);
                brown_pictureBox.Left = brown_pictureBox.Left + (e.X - currentX);
            }
        }

        private void brown_pictureBox_MouseUp(object sender, MouseEventArgs e)
        {
            isDragging = false;
        }

i use this code and it works very good , now i have a problem , i placed the pictureboxes inside a panel and now when i drag them out of it , the pictureboxes hides behind the panel.....

i tried brown_pictureBox.BringToFront(); but nothing happened.