利用图片判断QQ与旺旺在线状态：代码实例

    //aspx.cs页面代码
    public string GetQQState(string QQ)//获取QQ在线状态
    {
        WebClient client = new WebClient();
        byte[] data;
        try { data = client.DownloadData("http://wpa.qq.com/pa?p=1:" + QQ.ToString() + ":1"); }
        catch { data = new byte[0]; }
        switch (data.Length)
        {
            case 2329:
                return "<img src=\"/images/qq/on.jpg\" style=\"width:72px;height:22px;vertical-align:middle;\" alt=\"QQ在线\" title=\"点击我要购买即可联系\"/>";
                break;
            case 2262:
                return "<img src=\"/images/qq/no.jpg\" style=\"width:72px;height:22px;vertical-align:middle;\" alt=\"QQ离线\" title=\"点击我要购买即可联系\"/>";
                break;
            default:
                return "QQ在线状态未知！";
                break;
        }
    }
    public string GetTBState(string taobao)//获取旺旺在线状态
    {
        WebClient client = new WebClient();
        byte[] data;
        try { data = client.DownloadData("http://amos1.taobao.com/online.ww?v=2&uid=" + taobao.ToString() + "&s=1"); }
        catch { data = new byte[0]; }
        switch (data.Length)
        {
            case 4944:
                return "<img src=\"/images/qq/on.gif\" style=\"width:72px;height:22px;vertical-align:middle;\" alt=\"旺旺在线\" title=\"点击我要购买即可联系\"/>";