Process html files with HttpModule to catch 404 errors on IIS7

Question

I am having another problem with my HttpModule that handles exceptions. (cfr. my previous post: Custom HttpModule for IIS 7 for integrated )

All works well, but only for aspx pages.

The main reason we wanted to use this HttpModule is to handle 404 exceptions that occur when someone tries to go to a html page that doesn't exist. But my HttpModule only works for .aspx pages and it isn't triggered when a html file doesn't exist.

This is the configuration that I have set up in my web.conf file:

<system.webServer>
  <modules>
    <add name="AspExceptionHandler" 
         type="Company.Exceptions.AspExceptionHandler, Company.Exceptions" 
         preCondition="managedHandler" />
  </modules>
</system.webServer>

I have also tried adding 'runAllManagedModulesForAllRequests="true"' to the module node, and 'preCondition="managedHandler"' to the "add" node, but this also didn't work.

I have set the Application pool on which my web application is running to "Integrated" mode, because I found this a lot on google.

Is there another way to make my HttpModule handle exceptions that occur when visiting a non existing html page?

Thanks!

Answer 1

Having done a little research based on the answer of Alexander, I implemented IHttpHandler in my AspExceptionHandler as well.

My class now looks like:

public class AspExceptionHandler : IHttpModule, IHttpHandler
    {
        public void Dispose() { }

        public void Init(HttpApplication context)
        {
            context.Error += new EventHandler(ErrorHandler);
        }

        private void ErrorHandler(object sender, EventArgs e)
        {
            HttpApplication application = (HttpApplication)sender;
            try
            {
                // Gather information
                Exception currentException = application.Server.GetLastError(); ;
                String errorPage = "http://companywebsite.be/error.aspx";

                HttpException httpException = currentException as HttpException;
                if (httpException == null || httpException.GetHttpCode() != 404)
                {
                    application.Server.Transfer(errorPage, true);
                }
                //The error is a 404
                else
                {
                    // Continue
                    application.Server.ClearError();

                    String shouldMail404 = true;

                    //Try and redirect to the proper page.
                    String requestedFile = application.Request.Url.AbsolutePath.Trim('/').Split('/').Last();

                    // Redirect if required
                    String redirectURL = getRedirectURL(requestedFile.Trim('/'));
                    if (!String.IsNullOrEmpty(redirectURL))
                    {
                        //Redirect to the proper URL
                    }
                    //If we can't redirect properly, we set the statusCode to 404.
                    else
                    {
                        //Report the 404
                    }
                }
            }
            catch (Exception ex)
            {
                ExceptionCatcher.FillWebException(HttpContext.Current, ref ex);
                ExceptionCatcher.CatchException(ex);
            }
        }

        public bool IsReusable
        {
            get { return true; }
        }

        public void ProcessRequest(HttpContext context)
        {
            if (!File.Exists(context.Request.PhysicalPath)) 
            {
                throw new HttpException(404, String.Format("The file {0} does not exist", context.Request.PhysicalPath));
            }
                    else
            {
                context.Response.TransmitFile(context.Request.PhysicalPath);
            }
        }
    }

In the ProcessRequest method (required by the IHttpHandler) I check if the file exists. If it does not exist, I throw an HttpException that is catched by the HttpModule part of my class.

The system.webServer node in my web.config now looks like this:

<modules runAllManagedModulesForAllRequests="true">
            <add name="AspExceptionHandler" type="Company.Exceptions.AspExceptionHandler, Company.Exceptions" preCondition="managedHandler" />
        </modules>
        <handlers>
            <add name="AspExceptionHandler" type="Company.Exceptions.AspExceptionHandler, Company.Exceptions" verb="*" path="*.html" />
        </handlers>

I found the answer in in this post: HttpHandler fire only if file doesn't exist

Answer 2

you can try this

<httpHandlers>
    <add type="Company.Exceptions.AspExceptionHandler, Company.Exceptions" verb="*" path="*"/> 
    ....
</httpHandlers>

this help you to catch all request, but if reqest is made for existing page you need to pass it to standart handler