C#判断链接图片是否存在

public bool CheckUrlFileExist(string fileurl)
    {
        HttpWebRequest myReq = null;
        HttpWebResponse myRes = null;
        try
        {
            System.GC.Collect();
            System.Net.ServicePointManager.DefaultConnectionLimit = 100;

        myReq = (HttpWebRequest)WebRequest.Create(fileurl);
        myReq.Timeout = 1000;

        myRes = (HttpWebResponse)myReq.GetResponse();
        myReq.KeepAlive = false;
        bool isExist = myRes.ContentLength > 0;
        return isExist;
    }
    catch
    {
        return false;
    }
    finally
    {
        if (myRes != null)
        {
            myRes.Close();
            myRes = null;
        }
        if (myReq != null)
        {
            myReq.Abort();
            myReq = null;
        }
    }
}