Check if website is online with ASP.NET C#?

I would like to know how to check if a website is offline or online using C#?开发者_如何转开发

Try to hit the URL using HttpWebClient over an HTTP-GET Request. Call GetResponse() method for the HttpWebClient which you just created. Check for the HTTP-Status codes in the Response.

Here you will find the list of all HTTP status codes. If your request status code is statrting from 5 [5xx] which means the site is offline. There are other codes that can also tell you if the site is offline or unavailable.You can compare the codes against your preferred ones from the entire List.

//Code Example

HttpWebRequest httpReq = (HttpWebRequest)WebRequest.Create("http://www.stackoverflow.com");
httpReq.AllowAutoRedirect = false;

HttpWebResponse httpRes = (HttpWebResponse)httpReq.GetResponse();

if (httpRes.StatusCode==HttpStatusCode.NotFound) 
{
   // Code for NotFound resources goes here.
}

// Close the response.
httpRes.Close();

First off, define "online" and "offline". However, if your codebehind code is running, your site is online.

For my web apps, I use a setting called Offline, which admin can set on/off. Then I can check that setting programmatically. I use this Offline setting, to show friendly maintenance message to my users. Additionally you can use App_Offline.htm, reference : http://www.15seconds.com/issue/061207.htm

http://weblogs.asp.net/scottgu/archive/2005/10/06/426755.aspx

If you mean online/offline state that controls IIS, then you can control this, with custom Web Events (Application Lifetime Events)

http://support.microsoft.com/kb/893664

http://msdn.microsoft.com/en-us/library/aa479026.aspx

You can use Pingdom.com and its API's. Check the source code of the 'Alerter for Pingdom API' at the bottom of this page