正则获取图片路径

protected StringBuilder sb = new StringBuilder();
    protected void Page_Load(object sender, EventArgs e)
    {
        string str = QConnectSDK.CustomWebRequest.getResponse("/", QConnectSDK.Method.GET, null);
        Regex reg = new Regex("<img([^\\/>src]+)src=\"([^\"]+)\"([^\\/]*)\\/?>");
        MatchCollection mats = reg.Matches(str);
        Regex reg1 = null;
        string aa;
        foreach (Match mat in mats)
        {
            aa = mat.Value;
            reg1 = new Regex("src=\"([^\"]+)\"");
            sb.AppendFormat("<img src=\"/images/loading.gif\" orgsrc=\"http://www.xiaoyu365.com{0}\" />", reg1.Match(aa).Groups[1]);
        }

    }

 <img([^\/>src]+)src="([^"]+)"([^\/]*)\/?>