WEBDUDE

Custom Errors in IIS7

WebDude — Mon, 07 Sep 2009 06:21:32 GMT

Having recently moved over to IIS7, one of my stumbling blocks has been around custom errors.
This works really well in IIS6, but as soon as you move over to IIS7 seems to completely stop working in most cases.

Requests to folders or files without .aspx extensions seems to just throw a Server Error

This was less than ideal, so I set out to find out the right way to do this in IIS7.

You may be familiar with a section in your web configuration file named :

<system.webServer>

In IIS6 this section is totally ignored, but the minute you move to IIS7 this section becomes oh so important.
We generally setup our modules and handlers here, but there is another section we can add called:

<httpErrors>

Now this can also be controlled through the IIS7 interface, but here I'll show you how to do this in code.

Firstly, this element is locked at application server level.
This means you will not be able to modify it in your web configuration file unless you allow this in your application host configuration file.
If you’re unfamiliar with this file, you can think of it as IIS’s Application Configuration file.

Before you do this, please note:

It is highly dangerous to mess with this file and can take down every website on your entire web server. Please approach with caution!
Please back this file up before trying anything

Now that we have that out the way, you can find this file in the following location:

c:\Windows\System32\inetsrv\config\applicationHost.config

in this file navigate to a line that reads

<section name="httpErrors" overrideModeDefault="Allow" />

And alter the overrideModeDefault to be Allow

<section name="httpErrors" overrideModeDefault="Allow" />

Save this file, and you are now free to add HttpErrors to your web configuration file.
So, inside the system.webServer section add the following code

<httpErrors errorMode="Custom" existingResponse="Replace" defaultPath="/500/Default.aspx" defaultResponseMode="ExecuteURL">

  <clear />

  <error statusCode="404" path="/404/default.aspx" prefixLanguageFilePath="" responseMode="ExecuteURL" />

</httpErrors>

Now this is pretty much the magic that makes your 404’s (and 500’s) work properly.
You may now remove or comment out your existing customErrors section.

Disable button on post back – working with validators

WebDude — Mon, 26 Jan 2009 11:05:12 GMT

In the past I’ve written a post on how to disable a button on post back:

Disable button on past back

<script language="javascript" type="text/javascript">
<!--
   function disableAndPost()
   {
      <%= ClientScript.GetPostBackEventReference(btnDoSomething, "") %>;
      document.getElementById('<%=btnDoSomething.ClientID %>').disabled="disabled";
   }
-->
</script>

This works really nicely, until you try use this with ASP.NET Validators.

Fortunately, there is a simple work around for this.
We need to check is the javascription function Page_ClientValidate() is true or false.

This can be achieved easily by modifying the above code as follows:

<script language="javascript" type="text/javascript">
<!--
   function disableAndPost()
   {
      if (typeof(Page_ClientValidate) == 'function')
        if (Page_ClientValidate() == false)
           return false; 
      <%= ClientScript.GetPostBackEventReference(btnDoSomething, "") %>;
      document.getElementById('<%=btnDoSomething.ClientID %>').disabled="disabled";
   }
-->
</script>

This will exit out of the function if the form is not yet validated.
Simple as that!

ASP.NET Website working within a frame

WebDude — Wed, 21 Jan 2009 05:43:10 GMT

I recently was tasked with creating an ASP.NET Website that will run within a Frame on another domain.

Not realising the inherent problem with this method, I set about happily creating a website as I normally do oblivious to the impending problems about to be uncovered.
In development my website worked as expected, passed QA testing and was on it’s way up to production where it would finally be placed inside it’s frame for use.

So imagine the “Shock and Awe” when the application didn’t work what so ever. Like it couldn’t maintain a session.

So it turns out depending on Browser security settings, 3rd party cookies are disabled and websites within frames can not rely on cookies and can therefore not utilise session cookies.
Luckily however there is a simple solution for this.

All we need to do is add a p3p – Privacy Preferences Project - header which will indicate to the browser that this is in fact a site that can be trusted.
In essence this published a privacy policy which states what kind of information is collected and whether it will be used for forces of true evil or not.
Personally I don’t quite get it, because anyone intending on abusing this system can do just the same to get their pirate hacking sites to work.

But that’s not me, I behave, so I’m happy there’s a solution!
Well, enough pre-amble … let’s code!!

This is the header you have to:

HttpContext.Current.Response.AddHeader("p3p", "CP=\"IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT\"");

I utilise this by placing it into an HttpModule like follows:

    1 namespace WebDude
    2 {
    3     public class PrivacyPreferencesHeader : IHttpModule
    4     {
    5         public void Init(HttpApplication context)
    6         {
    7             context.BeginRequest += context_BeginRequest;
    8         }
    9 
   10         private void context_BeginRequest(object sender, EventArgs e)
   11         {
   12             HttpContext.Current.Response.AddHeader("p3p", "CP=\"IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT\"");
   13         }
   14 
   15         public void Dispose()
   16         {
   17 
   18         }
   19     }
   20 }

Reference this HttpModule in your Web.Config’s HttpModule section

<add name="PrivacyPreferencesHeader" type="WebDude.PrivacyPreferencesHeader, WebDude"/>

You can download the csharp source file here

Googling on the web, I found the same solution for some other languages thanks to this post

PHP
header('P3P:CP="IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT"');

JSP
response.setHeader("P3P","CP='IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT'")

Coldfusion
<cfheader name="P3P" value="CP='IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT'" />

GamerLobby syndicatable frame

WebDude — Tue, 25 Nov 2008 15:16:56 GMT

So we had a little experiment on the GamerLobby to create a frame displaying our matches that could be easily integrated into community sites out there. This is what it looks like:

Creating your own Unhandled Error Logging Module

WebDude — Wed, 17 Sep 2008 14:12:13 GMT

I'm a big fan of the ELMAH project which I utilise in my personal website GamerLobby.net
This is great for plugging into an existing website to catch unhandled exceptions, but not ideal when you want to log to an existing infrastructure.
So I set of on the task to create my own custom unhandled error logging module, and this is what I came up with.

HttpApplication contains various information that can be really useful when finding bugs or reviewing errors.
This can be nicely broken down into 5 categories:

Exception Information
Server Variables
QueryString Variables
Form Variables
Cookie Variables

Exception Information
This is available using the HttpApplication.Server.GetLastError() method.
This returns a System.Exception.

Server Variables
This contains a stacks of useful information. This includes info like: HTTP_REFERER, HTTP_USER_AGENT, PATH_INFO, REMOTE_ADDR and several other useful items to help trace the cause of the exception.
This is obtained from the HttpApplication.Context.Request.ServerVariables NameValue collection.

QueryString Variables
This will contain your querystring information.
This is obtained from the HttpApplication.Context.Request.QueryString NameValue collection.

Form Variables
This will contain any form information like that posted to the page that threw the exception.
This is obtained from the HttpApplication.Context.Request.Forms NameValue collection.

Cookie Variables
This will read any cookie information stored by your website.
This is obtained from the HttpApplication.Context.Request.Cookies HttpCookieCollection.

Now we can create a module to catch an unhandled exception, and gather all this information.
We start by creating a class that inherits from the interface IHttpModule.
In our Init method, we assign a delegate to our Error event of our HttpApplication context.

public class ErrorHandler : IHttpModule
{
   public void Init(HttpApplication context)
   {
      context.Error += Context_Error;
   }
}

Simple as that, any unhandled exception that occurs in our application, will be caught by our Context_Error event. Lovely!
Now let's setup our Context_Error void. Here we can gather all our information we need, and use it as we see fit

public void Context_Error(object sender, EventArgs e)
{
   //Cast sender to a HttpApplication
   HttpApplication app = (HttpApplication)sender;

   //Get the exception that occurred
   Exception ex = app.Server.GetLastError();

   //Get Querystring Variables
   NameValueCollection queryStringVariables = app.Context.Request.QueryString;

   //Get Form Variables
   NameValueCollection formVariables = app.Context.Request.Form;

   //Get Cookie Collection
   HttpCookieCollection cookieCollection = app.Context.Request.Cookies;

   //Get Server Variables
   NameValueCollection serverVariables = app.Context.Request.ServerVariables;

}

Now you can use this information to log away anything you need to help you troubleshoot the problem.
2 more methods which may help you loop through a NameValueCollection or a HttpCookieCollection

//Loop through a name value collection
private static void AddNameValueCollection(NameValueCollection nvc)
{
   if (nvc == null || nvc.Count == 0) return;
   if (nvc.HasKeys())
   foreach (string key in nvc.Keys)
   {
      //Get all your name values with 'key' and 'nvc[key]'
   }
}

//Loop through an HttpCookieCollection
private static void AddCookieCollection(HttpCookieCollection cookies)
{
   if (cookies == null || cookies.Count == 0) return;
   for (var i = 0; i < cookies.Count; i++)
   {
      var cookie = cookies[i];
      //Get all your name values with 'cookie.Name' & 'cookie.Value'
   }
}

Now you have bucket loads of information to look through in the event of an unhandled exception occurring in your website or web application!

HttpModules - Why using HttpApplication is a bad idea

WebDude — Mon, 08 Sep 2008 11:10:35 GMT

I was using Darksider's page optimisation module to clean up and optimise my sites HTML gamerlobby.net

This was working like an absolute champ up until the night I decided to go live. Leaving ELMAH for the last minute as it was so darn easy to implement, I started to struggle to get it to start logging.
It made no sense. Database created, Connection String present and correct, modules and handlers referenced. WHAT CAN IT BE.

So after hours of scratching my head and freaking out, I commented out Darksider's page optimisation module and voila ... Logging works again.

Very saddened by the fact my pages are no longer optimised, I was determined to work this one out. So finally today, I found the bug.
The page optimisation was utilising a using statement around the HttpApplication context. This in turn was swallowing the Context and breaking any other modules that attached themselves to HttpApplication events.

So we changed this:

using (var app = sender as HttpApplication)
{
   if (app.Context.CurrentHandler is Page)
   {
     app.Response.Filter = new PageCleanFilter(app.Response.Filter);
   }
}

To this:

var app = sender as HttpApplication;
if (app.Context.CurrentHandler is Page)
{
app.Response.Filter = new PageCleanFilter(app.Response.Filter);
}

Now all is logging again, and my page optimised!!
I'll be sure to pass this onto Darksider to update his post.

Organising that jungle of cables you're hoarding

WebDude — Wed, 03 Sep 2008 07:20:24 GMT

Several times I've seen these shows on TV about hoarders.
That seem like really sad people who don't know when to get rid of something, and I pity them.

So recently I moved house, and to my shocking surprise realised that I was in fact a hoarder to some extent.
Darn it!! I am one of those people. Well, I guess we are all to some extent. This brings me to the post.

So after unpacking one of my cupboards, I found tons and tons of cables that I just didn't want to get rid of.
Stuff that after thinking about it, was utterly useful. A huge mesh of telephone cable, RCA cables, aerial cables, power cables, old cell phone chargers, Vga cables and various others.
All these cables come in useful from time to time, and lot's don't. On top of this, when you do need a cable it's so darn difficult to get it out of the mesh, it's almost easier to run to the store and buy a new one. So determined to not throw away all my cable, I tried to create a way to organise the cables I needed, and here's what I came up with

I organised my cables/stuff into 4 categories:

AV Cables
- RCA's
- VGA
- Mini Jack to RCA
- TV Aerials
- S-Video
- Etc...
Data Cables
- IPod Data cables
- Hard Drive Data cables
- Fire Wire
- Phone/Camera Data cables
- Etc...
Power Cables
- Figure 8 cables
- Kettle plug cables
- Strange looking 3 hole cables
- AC Adapters
- Etc...
Old Cell Phone Stuff (needs refinement :))
- Old Cell Phones
- Old Cell Phone charges
- Old Cell Phone data cables
- Old Cell Phone memory sticks
- Etc...

Ok, now I feel like I'm getting somewhere!
So I separated all my cables as above, wrapped them neatly and cabled tied them.
I went on to place them into separate clearly labeled packets, and put all the packets into a box in my garage.

Now I have a system of no mess, I can find cables easily when I need them and most important of all ... My wife is not leaving me :)

I'd love to hear other people's suggestions or solutions to this problem

ServerVariables empty unless Debug

WebDude — Wed, 03 Sep 2008 05:46:39 GMT

Just had a really strange issue where I'm trying to log some ServerVariables when an error occurs.

The bug was when I ran the code without debugging, no ServerVariables were being logged.
If I went into Debug, and hovered my mouse over the ServerVariables variable, it had all the information I was looking for.
After that, it logged everything fine.

It seems called a Get on the ServerVariables variable was causing it to initialize properly.

After some further investigation, I found out I was relying on the NameValueCollection.HasKeys() method to see if I had any value.
This returns false. Just by calling Request.ServerVariables.Count, this completely fixes the problem.

So I changed the code as follows, and everything worked as expected

Changed From:

NameValueCollection nvc = Request.ServerVariables;

if(nvc == null) return;
if (nvc.HasKeys())
{
//Get ServerVariables Information
}

Changed To:

NameValueCollection nvc = Request.ServerVariables;

if(nvc == null || nvc.Count == 0) return;
if (nvc.HasKeys())
{
//Get ServerVariables Informatione
}

Disable button on post back

WebDude — Tue, 02 Sep 2008 05:22:30 GMT

Often post backs can take some time, and it appears to a user as if the browser is not responding causing the user to click the button multiple times.

In ASP.NET it is most simple to disable a button on click, and still post back to the page.
Here is how we can do this with an ASP.NET button.

First we'll create some Javascript to disable the button, but still call it's post back reference.
WE have to do this because once we disable a button, it stops the post back from occurring,
Let's create a button and take advantage of its OnClientClick property.
This property calls client side code before the page posts back.

<
asp:Button ID="btnDoSomething" runat="server" Text="Go" OnClick="btnDoSomething_Click" OnClientClick="disableAndPost()"/>

Now we can create a javascript block on the page to disable this button yet still call it's post back.
I'm going to use a Javascript and Inline C# script to accomplish this, but there are many ways you can do it.
I use inline script to retrieve the button's ID which is generated at runtime by ASP.NET, as well as call it's post back event reference.

<
script language="javascript" type="text/javascript">

</script>

Our first line calls the buttons post back event reference, the second line disables the button preventing it from being clicked again.

A nice added extra is once the page reloads, the button is no longer disabled as ASP.NET re-renders the page unaware of the client side property added to the button.

The next step would be to show a loading message or graphic during post back.

ASP.NET Custom Error not throwing 404

WebDude — Wed, 27 Aug 2008 10:59:04 GMT

So I had an issue with Google the other day when I noticed my site was no longer verified.
So I went through the general process of verifying but Google complained that it was not seeing a 404 with the following message

We've detected that your 404 (file not found) error page returns a status of 200 (Success) in the header

Now I found this very strange, as my custom errors handle my 404 so what's the problem. I had setup my web.config as follows:

<customErrors mode="On" defaultRedirect="/Error/">
<error statusCode="404" redirect="/404/" />
</customError>

So back to using Fiddler, I reviewed the status codes being returned when hitting my 404 page.
No suprise, a 302 was being returned instead of a 404. More specifically, in my rewriting environment this was returning a 200 which google was complaining about.

Now this only occurred when running in IIS, and when the missing page ended with an extension handled by the aspnet_isapi.dll.
So with re-writing turned on, that's EVERYPAGE in my entire website. Great!
Now as a side note, In Casini Web Server it seems a 302 is always thrown. So you can only replicate this through IIS.

So, onto THE FIX

Quite a simple one, we just need to specify the status code on our 404 page.
So I use a WebForm as my 404 and I can now set the status code in the code behind:

Response.StatusCode = 404;

This immediately fixed my problem and Google is happy again ... Don't we all love making Google happy

I searched around for a way to do this in an HTML file, but could not find one. If anyone knows please comment and I'll update the post.