How to use Phil's error reporting code

I’ve done a number of posts now on Phil Whinstanley’s error reporting class and this blog appears to be getting a lot of hits because of that which is pretty neat, as a result I’ve had a couple of people write to me asking similar questions about the code so I thought it would be an idea to write a little summary.

Where can I download the code?

It would appear that most of the old copies of Phil’s code have disappeared from the web, I’m not sure why so I’ve uploaded the versions I’ve got below. For convenience I have compiled the code into DLLs for those that don’t know/want to do this and I’ve also included the Visual Studio solutions. I’m not sure if these are based on the original codebase but I don’t think I’ve made any major alterations to these versions:

1 This is a version I was sent as his original including changes and example email was lost...

DLLs only:

If you have Visual Studio:

If you don’t have Visual Studio you can either download one of the above projects and delete the solution/project files or download the original WebException code. Ok, now you have the files :) -FWIW I can accept no responsibility for any of the files or the code, I just zipped them!

How to do I use the WebException class?

I’m now using a slightly modified version of the code to enable error reporting within AJAX (see: Reporting errors from AJAX using the WebException Class) which I’ll try and upload later but whichever version of the code you choose the use is pretty much the same.

Once you have referenced the DLL in your project (see: Importing/Referencing DLLs in Visual Studio) you will be able to use the WebException. As I’ve covered what you need to do to use the code from within an AJAX application in another post (see: Reporting errors from AJAX using the WebException Class) I’ll just cover how to use it to report global errors. To capture and respond to all application errors you will need to place this code within the global.asax, your project should automatically have one, if it doesn’t then you will need to add one.

Using the global.asax file, the first thing you need to do is add a reference to the DLL at the top of your code (this will allow you to call the methods and access the properties):

<%@ Import Namespace="ErrorReporting" %>

Next locate the Application_Error event handler, this is the method that handles all errors within the application (with exception of those thrown from within an AJAX application, read this post to report errors from within an AJAX application). Now replace your Application_Error and Application_PreRequestHandlerExecute handlers with (for more information on what I'm doing here see: ASP.Net WebException and Error Reporting useful code):

void Application_Error(object sender, EventArgs e)
{
    bool reportErrors = Convert.ToBoolean(System.Configuration.ConfigurationManager.AppSettings["SendErrors"]);

    if (reportErrors)
    {
        Exception currentError = Server.GetLastError();

        #region Deal with 404's

        //Redirect the user to a friendly page
        if(CheckForErrorType(currentError, "FileNotFound"))
            RedirectToFriendlyUrl("");

        #endregion
        #region Deal with Spambots

        if (CheckForErrorType(currentError, "System.FormatException"))
        {
            if (HttpContext.Current.Request.Form.Count > 0)
            {
                foreach (string key in HttpContext.Current.Request.Form)
                {
                    if (key.IndexOf("_VIEWSTATE") > 0 && HttpContext.Current.Request.Form[key].ToString().IndexOf("Content-Type") > 0)
                        return;
                }
            }
        }

        #endregion

        //Enable the trace for the duration of the error handling
        TraceContext t = HttpContext.Current.Trace;
        bool bCurrentState = t.IsEnabled;
        t.IsEnabled = true;

        #region Handle the Exception

        ErrorHandling.WebException WE = new ErrorHandling.WebException();
        WE.CurrentException = Server.GetLastError();
        WE.MailFrom = "[email protected]";
        WE.MailTo = "[email protected]";
        WE.MailAdmin = "[email protected]";
        WE.Site = "Your Site's Name or URL";
        WE.SmtpServer = "localhost";
        WE.FloodCount = 10;
        WE.FloodMins = 5;

        #endregion
        #region Choose what you're interested in

        WE.ReturnCache = true;
        WE.DrillDownInCache = true;
        WE.IncludeApplication = true;
        WE.IncludeBrowser = true;
        WE.IncludeEnvironmentVariables = true;
        WE.IncludeForm = true;
        WE.IncludeProcess = true;
        WE.IncludeQueryString = true;
        WE.IncludeRequestCookies = true;
        WE.IncludeRequestHeader = true;
        WE.IncludeResponseCookies = true;
        WE.IncludeServerVariables = true;
        WE.IncludeSession = true;
        WE.IncludeTrace = true;
        WE.IncludeVersions = true;
        WE.IncludeAuthentication = true;

        #endregion

        WE.Handle();

        //Return the trace to its original state
        t.IsEnabled = bCurrentState;

        //Redirect the user to a friendly page
        RedirectToFriendlyUrl("");
    }
}

protected void Application_PreRequestHandlerExecute(Object sender, EventArgs e)
{
    if (Context.Handler is IRequiresSessionState || Context.Handler is IReadOnlySessionState)
        ErrorReporting.SessionTracker.AddRequest("Pre Request Handler Execute"truetruefalse);
}

private bool CheckForErrorType(Exception ex, string errorText)
{
    if (ex != null)
    {
        //Check the exception
        if (ex.GetType().ToString().IndexOf(errorText) > 0)
            return true;
        else
            return CheckForErrorType(ex.InnerException, errorText);
    }
    else
    {
        return false;
    }
}

private void RedirectToFriendlyUrl(string Url)
{
    if (!String.IsNullOrEmpty(Url) && (Request.Url.Host.IndexOf("localhost") < 0))
        Response.Redirect(Url);
}

This will create a new instance of the WebException object, assign the various properties accordingly (you will need to configure these) and then finally handle the error.

That’s it! That’s all you really need to do to have super error reporting instantly installed in your application! If that wasn't enough it's overloaded with a couple of filters for you :). I recommend you read one of my previous posts I’ve added which overviews a few simple tips and tricks when using the WebException class to that improves on its functionality (see: ASP.Net WebException and Error Reporting useful code).

All that's left to do is to test it works (see below).

What should I get from it?

That’s the million dollar question! Once the WebException class has been added to your application you should receive an email every time the application throws an error (which of course means you’ll never get an email from the system!)

View an example of the email you’ll get with all outputs set to true.

More tips/Warnings!

Ok so it’s installed and you’re getting no errors through (because your codes perfect) but there are a couple of other little tweaks I would make to the WebException class to make it a little more useable.

Create a centralised class for it

A while ago I posted a set of “useful” tips for reducing the number of spambot related emails, redirecting the user etc (see: ASP.Net WebException and Error Reporting useful code). That’s fine until you start including the WebException class into multiple projects, managing tweaks to the codebase gets a little cumbersome (i.e. adding the spambot check to all our projects that use the WebException meant a couple of hours of copying and pasting). The work around for me was to wrap it all up into a central static method (see: Reporting errors from AJAX using the WebException Class). I did this rather than fiddling with Phil’s WebException class itself incase he ever got around to releasing another version which would mean a bunch of changes etc.

Limit the page request log

If you have a site where every user is likely to have a high page visit count with most of the pages involving some form of form submission then it may be worth limiting the number of request’s stored as we have found that without limiting these we start receiving very large emails (some topping 10MB).

The reason this is happening is because the session tracker logs all the form elements for the request so if you had i.e. a CMS that submits a page of content every other page request all that data will be stored in the tracker, sticking with the idea of a CMS, your typical text word is around 10bytes (see: How many bytes for...), so say the user writes 500 words per page (which isn’t really a lot) that’s 4.9Kb per form submission plus on the re-display of the page you've got ViewState... That’s just the data submitted by the user, around that, you’ve got all the form fields, field names, session info, query string etc, see how it starts to add up?

The solution is fairly straight forward, what you need to do is alter SessionTracker.cs1:

1I thought I'd done this in a project already but cannot find the source so this may not work.

public class SessionTracker
{
    public static void AddRequest(string Comments, bool DoForm, bool DoQueryString, bool DoCookies)
    {
        Request R = new Request();
        R.Time = DateTime.Now;
        R.Comments = Comments;
        
        if (System.Web.HttpContext.Current != null)
        {
            R.Path = System.Web.HttpContext.Current.Request.Path.ToString();
            if (System.Web.HttpContext.Current.Request.UrlReferrer != null)
            {
                R.Referrer = System.Web.HttpContext.Current.Request.UrlReferrer.ToString();
            }
            if (DoForm)
            {
                R.Form = System.Web.HttpContext.Current.Request.Form;
            }
            if (DoQueryString)
            {
                R.QueryString = System.Web.HttpContext.Current.Request.QueryString;
            }
            if (DoCookies)
            {
                R.Cookies = System.Web.HttpContext.Current.Request.Cookies;
            }
        }

        if (System.Web.HttpContext.Current.Session["RequestCollection"] != null)
        {
            RequestCollection RC = ((RequestCollection)System.Web.HttpContext.Current.Session["RequestCollection"]);
            RC.Add(R);
            if(RC.Count > 10)
                RC.RemoveAt(0);
            System.Web.HttpContext.Current.Session["RequestCollection"] = RC;
        }
        else
        {
            RequestCollection RC = new RequestCollection();
            RC.Add(R);
            System.Web.HttpContext.Current.Session["RequestCollection"] = RC;
        }
    }

    public static void AddRequest(string Comments)
    {
        Request R = new Request();
        R.Time = DateTime.Now;
        R.Comments = Comments;
        
        if (System.Web.HttpContext.Current != null)
        {
            R.Path = System.Web.HttpContext.Current.Request.Path.ToString();
            if (System.Web.HttpContext.Current.Request.UrlReferrer != null)
            {
                R.Referrer = System.Web.HttpContext.Current.Request.UrlReferrer.ToString();
            }
            R.Form = System.Web.HttpContext.Current.Request.Form;
            R.QueryString = System.Web.HttpContext.Current.Request.QueryString;
            R.Cookies = System.Web.HttpContext.Current.Request.Cookies;
        }

        if (System.Web.HttpContext.Current.Session["RequestCollection"] != null)
        {
            RequestCollection RC = ((RequestCollection)System.Web.HttpContext.Current.Session["RequestCollection"]);
            RC.Add(R);
            if (RC.Count > 10)
                RC.RemoveAt(0);
            System.Web.HttpContext.Current.Session["RequestCollection"] = RC;
        }
        else
        {
            RequestCollection RC = new RequestCollection();
            RC.Add(R);
            System.Web.HttpContext.Current.Session["RequestCollection"] = RC;
        }
    }

    public static void AddRequest()
    {
        Request R = new Request();
        R.Time = DateTime.Now;
        
        if (System.Web.HttpContext.Current.Session["RequestCollection"] == null)
        {
            RequestCollection RC = ((RequestCollection)System.Web.HttpContext.Current.Session["RequestCollection"]);
            RC.Add(R);
            if (RC.Count > 10)
                RC.RemoveAt(0);
            System.Web.HttpContext.Current.Session["RequestCollection"] = RC;
        }
        else
        {
            RequestCollection RC = new RequestCollection();
            RC.Add(R);
            System.Web.HttpContext.Current.Session["RequestCollection"] = RC;
        }
    }

    public SessionTracker()
    {
    }
}

Outputting the Trace with the WebException Class

I know this is something I’ve posted about in the past but since moving to version 4 of the code and .Net 2.0 I was no longer getting the trace in my lovely error reports, after a little digging I’ve found a solution, in addition to the code that I posted earlier about enabling the trace using C#, the web.config needs to be set as follows:

<trace enabled="true" requestLimit="100" pageOutput="false" traceMode="SortByTime" localOnly="true" />

Storing the WebException code in App_Code Dir

If you use the WebException class in an ASP.Net 2.0 site, be careful you don’t do what we did and throw the site online uncompiled with a compilation error as it won’t get reported. Luckily I found this issue on a test site but it’s still worth noting.

Personally I wouldn’t put the error reporting code in the App_Code directory as this means you’ll end up needing to maintain a plethora of files throughout various projects. Instead compile a separate DLL and include that in your projects, then if like me you find a nice addition to the error reporting code you can easily update all sites to the latest version!

Setup a simple generic test page

Nothing fancy, just a button that throws an exception will do:

TestErrorPage.aspx

<%@ Page Language="C#" %>


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">
    protected void btnError_Click(object sender, EventArgs e)
    {
        throw new ArgumentException("Test Error");
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Test Error Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <p><asp:Button runat="server" ID="btnError" Text="Throw Error" OnClick="btnError_Click" /></p>
    </div>
    </form>
</body>
</html>

Happy Error Reporting :) -I'm hoping this is the last time I need to blog about this code but what's the betting another post is around the corner ;)

Author

Tim

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