判断网络图片是否存在

    private bool IsExist(string fileurl)
    {
        HttpWebRequest myReq = (HttpWebRequest)WebRequest.Create(fileurl);
        HttpWebResponse myRes = (HttpWebResponse)myReq.GetResponse();
        if (myRes.ContentLength > 0)
        {
            return true; //存在   
        }
        else
        {
            return false;
        }
    }