while retrieving icon image from database in asp.net to show in treeview , the icon image width is so large . so, how to reduce width of icon image

public static Bitmap CreateThumbnail(Bitmap source, int thumbWidth, int thumbHeight, bool maintainAspect)
{
        if (source.Width < thumbWidth && source.Height < thumbHeight) return source;

        Bitmap image = null;
        try
        {
            int width = thumbWidth;
            int height = thumbHeight;

            if (maintainAspect)
            {
                if (source.Width > source.Height)
                {
                    width = thumbWidth;
                    height = (int)(source.Height * ((decimal)thumbWidth / source.Width));
                }
                else
                {
                    height = thumbHeight;
                    width = (int)(source.Width * ((decimal)thumbHeight / source.Height));
                }
            }

            image = new Bitmap(width, height);
            using (Graphics g = Graphics.FromImage(image))
            {
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
                g.FillRectangle(Brushes.White, 0, 0, width, height);
                g.DrawImage(source, 0, 0, width, height);
            }

            return image;
        }
        catch
        {
            image = null;
        }
        finally
        {
            if (image != null)
            {
                image.Dispose();
            }
        }

        return null;
}