How to debug a web appplication?


C

Carl Gilbert

Hi

I have implemented the ASP.NET Club Site Starter Kit on my 1&1 web
space.
I have recently been getting some errors where the page doesn't load
and just comes up blank. I have put a handler on Application_Error in
global.asax to email me whenever an error occurs. Sometimes I get upto
100 in an hour which is rather concerning.

I have looked at the error message returned but I can't seem to work
out what's causing the error.

How can I debug the application to track down the error? I have quite
a bit of experience with VB.NET so I understand the concept of break
points and stack traces but it all seems a bit scary when it's on the
web.

I have included the code I have in my global.asax and the error message
I get at the bottom of this post. Should I try running the app on
local host or is there some sort of component or change I can make
somewhere to track down the error online?

Note: I didn't write the error notification code. Theres a line which
logs to an event log. Would it help if I un-comment this and see what
that does?

Regards, Carl Gilbert

****** EVENT HANDLER ******

Protected Sub Application_Error(ByVal sender As Object, ByVal e As
System.EventArgs)
Dim objErr As Exception = Server.GetLastError.GetBaseException
Dim strMsg As String = "Error Caught in Application_Error
event\n" + _
"<br>Error in: <a href='" + Request.Url.ToString() + "'>" +
Request.Url.ToString() + "</a>" + _
"\n<br>Error Message:" + objErr.Message.ToString() + _
"\n\n<br><br>REMOTE_ADDR: " +
Request.ServerVariables("REMOTE_ADDR") + "</a>" + _
"\n<br>HTTP_ACCEPT_LANGUAGE: " +
Request.ServerVariables("HTTP_ACCEPT_LANGUAGE") + _
"\n<br>HTTP_REFERER: " +
Request.ServerVariables("HTTP_REFERER") + _
"\n<br>HTTP_USER_AGENT: " +
Request.ServerVariables("HTTP_USER_AGENT") + _
"\n<br>HTTP_COOKIE: " +
Request.ServerVariables("HTTP_COOKIE") + "\n\n\n<br><br>Stack Trace:" +
objErr.StackTrace.ToString


'EventLog.WriteEntry("Sample_WebApp",err,EventLogEntryType.Error);
Server.ClearError()
Dim strSbj As String = "BWBFC Application Error"
ClubSiteMailer.Mailer.Send(strMsg, strSbj)

End Sub

****** ERROR MESSAGE ******

Error Caught in Application_Error event\n
Error in: http://bwbfc.co.uk/bb/default.aspx\n
Error Message:Request for the permission of type
'System.Security.Permissions.FileIOPermission, mscorlib,
Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'
failed.\n\n

REMOTE_ADDR: 217.37.196.9\n
HTTP_ACCEPT_LANGUAGE: en-gb\n
HTTP_REFERER: \n
HTTP_USER_AGENT: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;
SV1; .NET CLR 1.1.4322; InfoPath.1; .NET CLR 2.0.50727; WinFX RunTime
3.0.50727)\n
HTTP_COOKIE: \n\n\n

Stack Trace: at System.Security.CodeAccessSecurityEngine.Check(Object
demand, StackCrawlMark& stackMark, Boolean isPermSet) at
System.Security.CodeAccessPermission.Demand() at
System.IO.Path.GetFullPath(String path) at
System.Web.Util.FileUtil.IsSuspiciousPhysicalPath(String physicalPath,
Boolean& pathTooLong) at
System.Web.Util.FileUtil.IsSuspiciousPhysicalPath(String physicalPath)
at System.Web.CachedPathData.GetConfigPathData(String configPath) at
System.Web.CachedPathData.GetConfigPathData(String configPath) at
System.Web.CachedPathData.GetConfigPathData(String configPath) at
System.Web.CachedPathData.GetVirtualPathData(VirtualPath virtualPath,
Boolean permitPathsOutsideApp) at
System.Web.HttpContext.GetPathData(VirtualPath path) at
System.Web.Security.UrlAuthorizationModule.IsUserAllowedToPath(HttpContext
context, VirtualPath virtualPath) at
System.Web.UI.Util.IsUserAllowedToPath(HttpContext context, VirtualPath
virtualPath) at
System.Web.SiteMapProvider.IsAccessibleToUser(HttpContext context,
SiteMapNode node) at
System.Web.SiteMapNode.IsAccessibleToUser(HttpContext context) at
System.Web.StaticSiteMapProvider.GetChildNodes(SiteMapNode node) at
System.Web.SiteMapNode.get_ChildNodes() at
System.Web.UI.WebControls.SiteMapDataSource.GetNodes() at
System.Web.UI.WebControls.SiteMapDataSource.GetPathNodeCollection(String
viewPath) at System.Web.UI.WebControls.SiteMapDataSource.GetView(String
viewName) at
System.Web.UI.WebControls.SiteMapDataSource.System.Web.UI.IDataSource.GetView(String
viewName) at
System.Web.UI.WebControls.Repeater.ConnectToDataSourceView() at
System.Web.UI.WebControls.Repeater.OnLoad(EventArgs e) at
System.Web.UI.Control.LoadRecursive() at
System.Web.UI.Control.LoadRecursive() at
System.Web.UI.Control.LoadRecursive() at
System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at
System.Web.UI.Page.ProcessRequest(Boolean
includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at
System.Web.UI.Page.ProcessRequest() at
System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) at
System.Web.UI.Page.ProcessRequest(HttpContext context) at
ASP.default_aspx.ProcessRequest(HttpContext context) at
System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&
completedSynchronously)
 
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C

Carl Gilbert

I also get this error quite a lot:


****** IMAGE FETCH ERROR ******
Error Caught in Application_Error event\n
Error in: http://bwbfc.co.uk/bb/imagefetch.ashx?size=1&imageid=118\n
Error Message:Object reference not set to an instance of an object.\n\n

REMOTE_ADDR: 198.36.87.81\n
HTTP_ACCEPT_LANGUAGE: en-gb\n
HTTP_REFERER:
http://bwbfc.co.uk/bb/Photoalbum_contents.aspx?Albumid=10\n
HTTP_USER_AGENT: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;
..NET CLR 1.1.4322)\n
HTTP_COOKIE: \n\n\n

Stack Trace: at ImageFetch.writeSingleImage(Int32 ImageID, Int32 size,
Stream output) at ImageFetch.ProcessRequest(HttpContext context) at
System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&
completedSynchronously
 
J

Juan T. Llibre

C

Carl Gilbert

Is there anyway to debug an application online?
I've put output logic in the global.asax but this isn't giving me enough
information. Plus, as I'm using shared hosting I have virtually no access
to the server to perform any monitoring.

Carl
 
J

Juan T. Llibre

re:
Is there anyway to debug an application online?

You mean remote debugging.

Yes, but it involves manipulating the server
( installing Visual Studio server-side components on it )

See :
http://msdn2.microsoft.com/en-us/library/cx6214f0.aspx

The problem for you, of course, is that since you're on shared hosting,
it's highly unlikely that your hoster will agree to installing anything on the server.



Juan T. Llibre, asp.net MVP
aspnetfaq.com : http://www.aspnetfaq.com/
asp.net faq : http://asp.net.do/faq/
foros de asp.net, en español : http://asp.net.do/foros/
===================================
 
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