检测远程URL是否存在的三种方法

最新推荐文章于 2022-08-22 11:23:36 发布

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#url #string #null #object

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本文介绍了使用HttpWebRequest、XmlHttp及Sockets三种方式检查URL是否有效的方法，并提供了具体的C#实现代码。通过这些方法可以判断指定URL所指向的资源是否存在。

private void Page_Load(object sender, System.EventArgs e)
{
    string url1 = "http://dotnet.aspx.cc/";
    string url2 = "http://dotnet.aspx.cc/Images/logo.gif";
    Response.Write("<li>方法1：");
    Response.Write(url1 + " 存在：" + UrlExistsUsingHttpWebRequest(url1).ToString());
    Response.Write("<li>方法2：");
    Response.Write(url1 + " 存在：" + UrlExistsUsingSockets(url1).ToString());
    Response.Write("<li>方法3：");
    Response.Write(url1 + " 存在：" + UrlExistsUsingXmlHttp(url1).ToString());

    Response.Write("<li>方法1：");
    Response.Write(url2 + " 存在：" + UrlExistsUsingHttpWebRequest(url2).ToString());
    Response.Write("<li>方法3：");
    Response.Write(url2 + " 存在：" + UrlExistsUsingXmlHttp(url2).ToString());
}
private bool UrlExistsUsingHttpWebRequest(string url)
{
    try
    {
        System.Net.HttpWebRequest myRequest = (System.Net.HttpWebRequest) System.Net.WebRequest.Create(url);
        myRequest.Method = "HEAD";
        myRequest.Timeout = 100;
        System.Net.HttpWebResponse res = (System.Net.HttpWebResponse) myRequest.GetResponse();
        return (res.StatusCode == System.Net.HttpStatusCode.OK);
    }
    catch (System.Net.WebException we)
    {
        System.Diagnostics.Trace.Write(we.Message);
        return false;
    }
}
private bool UrlExistsUsingXmlHttp(string url)
{
    //注意：此方法需要引用Msxml2.dll
    MSXML2.XMLHTTP _xmlhttp = new MSXML2.XMLHTTPClass();
    _xmlhttp.open("HEAD", url, false, null, null);
    _xmlhttp.send("");
    return (_xmlhttp.status == 200);
}

private bool UrlExistsUsingSockets(string url)
{
    if (url.StartsWith("http://"))
        url = url.Remove(0, "http://".Length);
    try
    {
        System.Net.IPHostEntry ipHost = System.Net.Dns.Resolve(url);
        return true;
    }
    catch (System.Net.Sockets.SocketException se)
    {
        System.Diagnostics.Trace.Write(se.Message);
        return false;
    }
}