png image but background is not transparent

        public void ShowImage(string imagePath)
        {
            Bitmap image = new Bitmap(imagePath);

            
            image.MakeTransparent(Color.Transparent);

            PictureBox pictureBox = new PictureBox
            {
                Image = image,
                SizeMode = PictureBoxSizeMode.AutoSize, 
                
            };
            this.Controls.Add(pictureBox);
            this.ClientSize = pictureBox.Size;
        }