class html_parser
    {
        private string text = null;
        public void setText(string text)
        {
            this.text = text;
        }
        public string getImg()
        {
            var image = "no_image.png";
            var s_text = "<img src='";
            var e_text = "' alt='";
            if (text.IndexOf(s_text) != -1)
            {
                int c = (text.IndexOf(s_text) + s_text.Length);
                image = text.Substring(c, (text.IndexOf(e_text, c) - c));
            }
            return image;
        }
    }