//JavaScript中的代码：
 
var re = /src=\"([^\"]*?)\"/i;
var arr = str.match(re);
if (arr != undefined && arr.length > 0) {
    insertHtml = arr[1];
}

/// <summary>
        /// 获取字符串中img的url集合
        /// </summary>
        /// <param name="content">字符串</param>
        /// <returns></returns>
        public static List<string> getImgUrl(string content)
        {
            Regex rg = new Regex("src=\"([^\"]+)\"",RegexOptions.IgnoreCase);
            var m = rg.Match(content);
            List<string> imgUrl = new List<string>();
            while (m.Success)
            {
                imgUrl.Add(m.Groups[1].Value); //这里就是图片路径                
                m = m.NextMatch();
            }
            return imgUrl;
        }