Application_Error firing even for handled exceptions

Question

I have some code to display a button if a URL exists:

try { string dashboardURL = Config.RootUrl + "/Dashboard/Default.aspx"; WebRequest req = WebRequest.Create(dashboardURL); WebResponse response = req.GetResponse(); btnDashboard.Visible = true; } catch (Exception) { btnDashboard.Visible = false; }

However, when debugging, req.getResponse() causes Application_Error to fire. I checked the exception being caught here and it is a System.Net.WebException. My understanding was that Application_Error is fired for unhandled exceptions.

If I change the code to force an exception as follows:

try { string dashboardURL = Config.RootUrl + "/Dashboard/Default.aspx"; WebRequest req = WebRequest.Create(dashboardURL); int j = 0; int i = 1 / j; WebResponse response = req.GetResponse(); btnDashboard.Visible = true; } catch (Exception) { btnDashboard.Visible = false; }

then Application_Error is not fired, which is good. Is there something particular about handling errors with GetResponse() that always causes Application_Error to fire, even if the exception is handled?

As the name implies 'Application Error' is an error issued at the application level. — akhil
– akhil, Commented Jul 4, 2012 at 9:30
Is Config.RootUrl + "/Dashboard/Default.aspx" in the same server/application? — Andrey Shchekin
– Andrey Shchekin, Commented Jul 11, 2012 at 3:32

l1e3e3t7 · Accepted Answer · 2012-07-11 03:04:10Z

In Application_Error check the exception:

var exception = Server.GetLastError();

It is impossible that Application_Error is fired with this code. Your exception must be after this try/catch Block.

Also try to Clean and Rebuild your solution, or force the Designer File to get recreated (Change something on aspx file).

I tested your code on different ASP.NET Version, even on MVC3/MVC4 Environment and Application_Error is never fired!

Andrey Shchekin · Accepted Answer · 2012-07-12 22:57:26Z

Is the /Dashboard/Default.aspx in the same server/application?

If so then processing of that request can cause an error that will be captured by the Application_Error. The reason is that by doing GetResponse() you are doing a HTTP request, and any exceptions that happen while processing the request on (potentially) remote server will not be handled by try/catch on the calling code. In your special case remote server = local server, but the idea does not change.

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