检测远程URL是否存在的三种方法

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;

}

}