Universe of a Developer

Update 15 Dec, 2008: This issue disappeared in IE8 partner build ('Pre-RC1') 8.0.6001.18343

In continuation to the post about IE 8 beta 1 issue, I figured that I still have the problem in my system even after upgrading to IE 8 beta 2. Only this time, I was able to generalize the problem very much.

Here’s what I found:

The problem is that window.external object (in JavaScript) doesn’t seem to have the correct reference to one of browser object (or at least that’s what I think so). Hence all methods of this object throws me an runtime script error.

Because of this, following actions fail in IE 8 beta 2 for me

1. Opening New tab – the previous post
   Though this doesn’t happen every time, but when it happens the code breaks at

   window.external.BuildNewTabPage(); 

2. Adding Service (Search provider, accelerators, etc) from http://www.ieaddons.com/en/searchproviders/
   breaks at

   window.external.AddSearchProvider();

   or

   window.external.addService(); 

3. The very first time, I open IE 8 beta 2 or the once after I 'reset' settings and open the browser again, in the 'Customize Search providers' & 'Customize Accelerators' page.
   
   • http://www.microsoft.com/windows/ie/searchguide/en-en/default.mspx?dcsref=http://runonce.msn.com/runonce2.aspx#
   • http://ie.microsoft.com/activities/en-en/Default.aspx
4. Especially in the 'Add Search Provider' page, in the section 'Create Your Own', when I add a custom search, it throws me an error "Unable to add search provider. The Create Your Own tool requires Internet Explorer. [32811]". See screenshot 3 below.

My UserAgent

I thought probably my UserAgent string is corrupt, but here it is… and I don’t see any problem with this.

“Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; InfoPath.1; 
.NET CLR 2.0.50727; FDM; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)”

Screenshots:

(1)   This screenshot is taken in the IE Gallery web site with error pop up from the site & the ‘About Dialog’. This is just a consequence the the problem I mentioned above, that window.external is not having correct reference. See code in below screenshot to understand.

(2)   This screenshot shows the exception details & the point were the exception is thrown in the IE Gallery website. The error number is “-2147319765”. A quick search on the web lead to nowhere.

(3) This happens in the ‘Add Search Provider’ –> Create Your Own search provider section. It’s strange that it says that I need IE to run this.

Seeking help at the IE Forum

I’m (again) going to post the problem in IE forum and this time I hope to see a different answer. The solution given to my previous post didn’t work at all.

Update: The issue is posted in IE Forum here.

Does anybody experience same issue in your system? Comment back…

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For a long time (quite a long time for an issue of such small size) in my project, we had this issue: file downloaded over SSL connection fails with strange error. After hunting in various woods (read articles) in several planets (read web sites), I found that solution was nowhere to be found easily but it was available as part of the application already.   

Here's the scenario:

    The application is written in ASP.NET/ C# 2.0 and it runs over SSL (HTTPS) in production. User is allowed to upload a file in a certain module in the application (say, Profile -> Options page). A link in the home page of every user is the provision to download this file. That is all - no big fuzz in the implementation as such.
    There are other few environmental setups which influenced this particular issue to slip till the production release The development environment was not using SSL certificates for obvious reasons; I mean who would want to set up a certificate for a dev environment? (It turned out, at least in QA environment it helps when the exact production settings are simulated - this is one more thing we overlook.)

File Download Issue:

When the application moved to QA environment, there were two types of errors experienced. The scenario goes like this: The user clicks on the link (to download the file) one of the following might occur

1. IE throws an error “Internet Explorer cannot download ABC.XYZ from www.mycompany.com” and does not even download the file

   
   The error message being "Internet explorer cannot download file from site. Internet explorer was not able to open this Internet site. ..."

2. IE shows the ‘Open/ Save’ dialog
   1. When ‘Open’ is clicked, the file opens in the appropriate editor (say Adobe Acrobat reader) and shows ‘File not found error’
      On inspection (using Sysinternals FileMon tools), we found that file is deleted by the IE browser as soon the ‘open’ button is clicked on the dialog. This is not the case in FF browsers
   2. When ‘Save’ is clicked, things go smooth as expected.

The issue #2 was not seen lately, so I didn't give it a priority. I'll talk about how issue #1 was solved below.

‘Code’ Behind:

Here are few details about the application...

1. Application is based on ASP.NET/C# 2.0 deployed on WinServer2003/HTTPS (Production/ QA environment). We use normal FileUpload control in ASP.NET for uploading the file.
2. The uploaded file is stored in the database in ‘Image’ type field of one of the tables. Database is run on SQL Server 2000
3. On click of the link to download, the file is read from the database and streamed to the HTTP Response using appropriate headers (see attached code: entity class and utility class)

Initial Research:

The initial research didn’t lead to any place meaningful – couple of support KBs, few forums, and couple of blogs – but nothing seemed to give correct solution. Here are the links that I ended up in the initial search!

• http://support.microsoft.com/?kbid=319032
• http://support.microsoft.com/default.aspx?scid=kb;en-us;316431
• http://nilangshah.wordpress.com/2007/05/28/successfully-stream-a-pdf-to-browser-through-https/
• http://it.toolbox.com/blogs/paytonbyrd/successfully-stream-a-pdf-through-https-1554

I did find something interesting – that too in our intranet projects portal’s FAQ section – which again didn’t direct me to any solution but gave few reasons why it was a browser issue and few links which ‘proved’ that it wasn’t anything to do with code. (All these actually convinced me that there nothing we could do to solve this )

Understanding how the wheel works and extend it to my issue:

I really wanted to do a ‘root cause analysis’ for this issue as it was bothering me for a significant time, I knew there is one another similar feature wherein the application throws up the PDF file to the user in the ‘Open/ Save’ dialog.

When I found how it was implemented, I was surprised and shocked! – surprised because it was lying all along in the space place much near to what I was looking for and shocked because this particular way to implementing the feature was hidden due to the fact that the faulty code which I’ve been working on lately was an initial (aka 1^st release) implementation which now has surpassed about 8+ releases.

So I didn’t even imagine doubting the component code that was supposed to achieve the expected behavior (it failed to do anyway) – and all these took some quite a humongous amount of effort – which I feel should not have been wasted given that one another working solution for similar problem is there in the application already! Well, whatever, we got what we wanted – scrutiny later.

Solution:

The solution itself is very simple (at least in our case).

1. There should a temporary location which the website can access with RW permissions
2. Create a virtual directory (in case of Win server 2003, create within the website) and make it point to the temporary location. Let’s call this ‘\tmpFolder’
3. Create a HTTP Handler class (inheriting IHttpHandler) you can refer to this KB
4. In <system.web> section of config file, add httpHandlers, like the given below

  <system.web>
    <!-- This is used for File Download -->
    <httpHandlers>
      <add verb="*" path="FileRetrieveHandler.aspx" 
           type="MyNameSpace.FileHandler, MyNameAssembly"/>
    </httpHandlers>
    <!-- ... Rest of System.Web section -->
  </system.web>

5. When you to open the file to the Response stream, do the following instead of directly writing to the Response stream
   1. Write the file to the temp location
   2. Redirect the response to the custom http handler by passing the filename also

6. I’m sure this could be optimized for performance and security, but I keep it open for comments! J

Okay, the main focus here should the use of HTTP handler. The reason why temp folder was used, in my case, is that similar solution was already implemented in the application. So instead of steps 1 and 2, one could even choose to read the file inside the HTTP handler or use a wrapper that do the job as you wish!

Couple of more issues noticed:

When the file being downloaded has some specifics characteristics, different browsers behave differently – this was also quite interesting… For e.g. lets take the file name as "My F#& # .pdf"

1. In IE 7 (or IE 8 b1), the white space is replaced with underscore. Ref this.
   1. In our case the filename in open/ save dialog becomes 'My_F_&___.pdf'
   2. This cannot be fixed – (rather, shall not be! Since there is no correct solution and is by design in IE7 and IE8 beta1)
2. In FF, the final downloaded file name was just “My” – the part of file before the first white space. FF forum blames IE for not implementing prescribed international standard. Read this.
   1. We’ll follow the standard mentioned in RFC 2231 of IETF, as recommended by FF forum, which works pretty fine in any situation on any browser!

I’ve submitted this to IE forums here, let’s see what happens next!

Few things learned in the course of finding the solution:

1. How to install, configure and issue a SSL certificate and configure website to use HTTPS - from here
2. Detailed look up on HTTP Handlers and different ways to implement/ enforce file download

More comments and critics welcome!

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1. Installed IE7 on winxp sp2 (upgraded from default IE6)
2. Installed IE8b1
3. Uninstalled IE8b1, IE7 (reverted to default IE6)
4. Installed IE8b1 (directly from IE6 to IE8b1)

-- Count of Fields

SELECT COUNT(FieldGroups) DiffGroupsCnt FROM (

      SELECT COUNT(FieldCnt) FieldGroups  FROM (

            SELECT COUNT(a.FieldID) FieldCnt, a.CustomerID FROM CustomerFields a

            WHERE a.CUSTOMERID IN ( A , B , C , D )

            GROUP BY a.CustomerID

            ) CustFieldGroups

      GROUP BY FieldCnt

) DifferenceGroups 

2. How to find if all the selected Customers have same field setup?
i.e. They should have same number of fields (which is achieved by the above solution) and also the fields tied up to each customer should also be same.
In general terms, How to find if the list of values of particular field is exactly same among all the specified class or group of values.

Figs: with sample data: For this problem,  Fig (a) & (c) are True condition, Fig (b) & (d) are False condition.
[Photo is also attached at end of the post]


For this, we were able to pickup a solution something VERY much similar to the solution for problem 1.

-- Field Setup

SELECT COUNT(FieldGroups) DiffGroupsCnt FROM (

      SELECT COUNT(CntOfCust) FieldGroups  FROM (

            SELECT COUNT(a.CustomerID) CntOfCust, a.FieldID FROM CustomerFields a

            WHERE a.CUSTOMERID IN ( 21, 22 , 11 )

            GROUP BY a.FieldID

            ) CustFieldGroups

      GROUP BY CntOfCust

) DifferenceGroups

It was real fun to do something challenging!
If you have read carefully, you might have noticed that the order of the fields itself is not taken into consideration. Let see who can come up with query for such a scenario

Before anyone starts the development process in the web application projects, I feel they should definitely have a look at this...

http://samples.gotdotnet.com/quickstart/aspplus/doc/perftuning.aspx

The article starts with

             “Any programming model has its common performance pitfalls, and ASP.NET is no exception…

Now making them better or worse is in the hands of the project team as a whole, but developers in particular.

Having these in our mind will not only increase the performance of the web application but also help us,

• develop a robust development environment during design time
  
• understand adapt best practices
• overall, become a better web developer
  

Just thought it would be useful to revisit our basics on web development!

1129     0          -1         Information                    2007-03-22 19:11:43.377            <server_name>            <some_application_domain>      4716     c:\windows\system32\inetsrv\w3wp.exe   NULL    5900            Invalid length for a Base-64 char array. -   Timestamp: 3/22/2007 7:11:43 PM  Message: Invalid length for a Base-64 char array. -   Category: <some_category>  Priority: -1  EventId: 0  Severity: <some_severity>  Title:  Machine: <some_machine> Application Domain: <some_application_domain>  Process Id: 4716  Process Name: c:\windows\system32\inetsrv\w3wp.exe  Win32 Thread Id: 5900  Thread Name:   Extended Properties: Username - Unauthenticated  StrackTrace -   Source -   InnerExceptionStackTrace -    at System.Convert.FromBase64String(String s)    at System.Web.UI.ObjectStateFormatter.Deserialize(String inputString)    at System.Web.UI.ObjectStateFormatter.System.Web.UI.IStateFormatter.Deserialize(String serializedState)    at System.Web.UI.Util.DeserializeWithAssert(IStateFormatter formatter, String serializedState)    at System.Web.UI.HiddenFieldPageStatePersister.Load()  InnerExceptionSource - mscorlib 

1. When some kind of encryptions (for eg: text for passwords) are used and  that are basically stored as Base-64 types (data type to stored special encoded string). Each Base-64 types are actually made of 3 bytes. Hence when processing these type of data, when it’s not in multiples of 3, such exceptions occur. 
2.  The ViewState is also stored in encoded Base-64 format. Another possible victim for this exception.

Resolving the problem reported…:

*Anyway, with the limited amount of exception details that was being mentioned, it’s clear that the exception occurred due to some loss/ truncation in the stored View State information.

(Because the stack trace information starts from the method “System.Web.UI.HiddenFieldPageStatePersister.Load()” which is nothing but the method used to load the ViewState (during Post back) from the HTML.) 

>> Though this does not seem to be exception of type “Invalid_Viewstate_Client_Disconnected” – which actually occurs when the ViewState is corrupt during post back from client, we can’t avoid this option either.

• The exception details given are not actually sufficient to find the exact point of problem (like IP, User-Agent (browser used), view state itself, path of the requested page).  Now, there is a Hot Fix available, to enhance the amount of exception details logged. (This does not fix any problems though )

 Possible scenarios which would have caused this problem:

1. The ViewState of the page is too long for the page to hold (limited by the MaxHTTPRequest length specified in web.config) and the view state gets truncated in transit. But this will be less probable since the web site had the MaxHTTPRequest length to 10MB citing some huge file uploads.
   1. Anyway, You can try to slightly lessen this with ViewState Compression techniques. Implementing this is fairly simple.
2. In a page where there are significant amount of ViewState stored (for eg: Pages with drop down having huge amount of data which you can’t avoid), the user tried to click the button more than once, causing multiple request to be fired and even this would have truncated the View State that’s being posted back to the server.
3. Another worst possible case would be some one trying to hack into by tampering the view state of your web page 

Exception handling?

Ok, finally…:

>> Hence, Scenario Case 1 can be controlled only to a limit (the limit you set as maximum HTTP Request size). Case 2 can not be controlled the web site host and Case 3, no way!  Don't worry, it doesn't matter.

 -- EOM --

Any better methods/ fixes available? 

• The way methods are called
• The way and process of storing temporary objects (cache and session objects)
• Common functionality for the application (eg: authorization for all the pages, mailing component, etc.)
• Performance based tweaks (like ViewState compression, huge data load on client, etc.)

        In the log, I used to add these details: Obviously date (), amount spent on a particular item, item description (which can be simple description or header for set of items), etc.. 
        This application will be windows based to start with and it's v2.0 will be targetted on adding a webapp/web services interface so that users can log their items even while out for vacation just using the Internet.

       I've got the DB design as such ready. Here's the XML Schema for the same.

[Same XML format is used to represent database schema by most of the schema generators. So, I put this up in a standard format.  Here's one place where you could find the Schema definition ]

 

[Update: XML File uploaded here] 

            Yesterday(02, Oct 2006) night on my way back from Hyderabad, after attending 'MS Stud Partners meet', I was travelling back to Bangalore in a ksrtc 'volvo' bus. I started my journey at 2000 hrs, at that time I didn't know I'm going to face one of my lifetime thrilling experience. I got my seat in the right side of the bus, third row from the driver's seat. It was a semisleeper and obviously, I thought I would enjoy the trip. After having the usual 'pitstop' around 1000 hrs, and later watching the telugu movie screened in the bus, I went to sleep around 0100 hrs (just 1 hour to face-off).

            It was exactly 0205 hrs in my watch  - I was deep asleep, when I heard people screaming... I felt the bus was sliding towards my right side. A sudden jerk... I was in the air for a moment.. my spectacles flew off.. I could hear glass pieces shattering and falling on my head... while making a 270* rotation, I was pretty concious to hold one of my hand on to the seat handle, even though I had bad blow on some parts of my body. When the bus came to a halt (literally...), I could see my bloody hands. People were screaming like anything. Immediately, I thought "Don't wait! get out and find help!! Quick". Just one shake and wipe off! and I started taking up the rescue procedure that I had learnt sometime back. I didn't have much time for myself, just ensured my two and my  was there in right place where I kept in my pant pocket and moved on...

            0215hrs: While trying to move out of the bus, there was this little kid right before me, trying to move out, but he stepped on the window glass that broke off; I clinged his hand, later realizing a small glass particle tearing my left index finger.. (ouch!) I moved out and could see the bus which was lying about 7-10 feet below the road level. It was gettin worse when I found very low signal in my AirTel mobile. I didn't reach border of Karnataka, so Hutch was out of thought. I found another guy dialing the emergency "112" in his BSNL mobile.

            After ensuring enough people were there to help others, around 0230 hrs, I climbed up to the road, just to hear "Hey! you know there is this accident..", I thought, "Come on! I need help!!" The vehicles passed by did stop on that spot, but just to take a look what was happening. I was so angry, that I jumped off to the middle of the road and stopped the vehicle, gave them the details of my bus lying 10 feet down, asked them to just inform this in the next petrol bunk/ checkpost.. I could find 4-5 people like me trying to offer help (nope! they weren't outsider, but the passengers themselves)

            One from the crowd offered a ride to the nearest police station. I was ready to go along with another person, but he asked me stay back in the spot and help out others lying down. My next worry was to bring everyone to the top. No one was ready to get down again; I jumped off (and eventually fell down making few more injuries to myself, but after seeing that, few more people started coming down). First off, I informed everyone help is on the way not to worry. Then, started consoling children there and took them to the roadside. I could see the driver unconcious, but people there were already on their way to get him on correct position. This was happening for a while.

            Later, people were very much concerned about their luggages; piled up underneeath the bottom of the bus. This was pretty difficult to handle! The top and bottom side of the bus was on the left and right side, making it difficult to climb. Fortunately, the luggage door was open. I started climbing up, but people asked me to wait till help arrived( which I was not hoping atleast anytime soon then). Finally, I got this person with the same name as mine(call it coincidence! phew!) and we both climbed to the door. Then that guy hesitated to get down, because the only light that was glowing started flickering and it was about to burnout! No moment to waste, I literally jumped into the place and started moving the luggages out. As soon as I climbed up, the lights turned off. (Every sequence was like as if watching a movie in virtual reality! I could still can't believe I made it.)

            Only after people and things were brought out from the bus safe, I started worrying about me.. yes, then I realized I was wounded little badly. I had no choice but to wipe out and start moving. Once I got confirmed help is on the way, I and few others whom I worked with, got into another bus to Bangalore. The accident spot was somewhere on the highway after ananthapur (AP).

   Today after getting medicated, I'm in my room. I don't know what to feel? the pain? satisfaction? relief? luck? whatever you call it, this is one eventful day I couldn't forget - the way I acted , the things I experienced...

From my post<link to the post> in my Tech Blog (http://thespoke.net/blogs/praveenkumar),

"Yesterday, I had opportunity to attend ISV Community  Days at Royal Orchid, Bangalore. The one difference for me in this event isthat I was representing the company I work for now. Myself and few of my friends were there. This ISV Community Days event is conducted by Microsoft regularly for demonstrating new technologies and tools to the software vendors. This time it was WPF, Microsoft Office 2007 system.

Here's the developer related content.

<soon to be updated>

• Basic difference you should know between VS 2003 and VS 2005
• ASP.NET 2.0 working model
• ASP.NET 2.0 basics (Pages, Partial classes, Code Separation, etc..)
• + An virtual Lab with example of creating an website in VS 2005

+> Praveen Kumar

1. Start -> Run -> services.msc
2. Scroll down to "Terminal Services"  (You know, this one was disabled!   which was supposed to be running)
3. (You guessed it!) Start this services. Set the startup "startup type" in "properties" of this service to manual or automatic.

1) Introduction to F# Part1

2) Introduction to F# Part2

hmm. I wonder what's the next big thing?

 

Try out this puzzle & try to reach out to Page 8(minimum), try to reach
till page 23.

http://www.freestuffhotdeals.com/hacker/1.html

 

It's quite interesting and fun. Though not techie.

Recently, I don't know why, but ASP.NET got my attention. At the right moment, when I started practising on few web apps (ASP.NET Web Applications), I got an oppurtunity to build up a website for Book Shopping.

Here are the specs in brief:

The site design is ready with wireframe.  
                           So, few CSS based rework would make it ready for  ASP.NET code

 Basic operations like, user/ admin login, view/search for books, cart management, and database management(for admin)

 This should be easy considering Microsoft Enterprise Library in hand. Although had to take care of database operations, the challenge was in making the website operational. Being first complete website built by me in ASP.NET, I'm trying to be simple and clean in the implementation ;)

After quite a long break in developing a complete application in .NET since my iTrust project (that won the nations' Best Project), here a small project that will focus on software engg concepts as well.

Alright, lets talk software engineering now along with the language of .NET

A brief description "
           Develop a web application for online publishing agency. The application should accept registration from public for specified list of e-magazines.
Application will have a registration page and confirmation page. A summary page for admin to view # number of registrations by e-magazine
Registration form will accept name, address, email-id, and selection list of e-magazines (C# Journal, Web programming with ASP.net, XML Programming with .Net …)

The requirements looks as simple and here's how my design goes.

Project: iMag - 'Your Daily dose of Technology'

P.S: I entend to keep this entire project very simple, yet adhere to SE Concepts so that implementation is piece of cake. Pseudo codes are available whereever necessary.

Disclaimer: The techniques used are customized and doesn't follow any particular methodology.

I assumed my design should adhere to the following target in Extensibility:

• Assumed SQLServer only (cannot extend to other db)
• Addition of new ui components facilitated
• Assumed Only new registrations
• But extensible to update order details
• Users can be added dynamically and the passwords are hashed and stored in DB

Design:

DB

Database is specified generic; I implemented in SQLServer

• Subscriber (sid, pwd, sname, saddr, semail)
• MagColl (mid, mname, msubcost)
• Order (onum, sid, mid)
• AdminLogins (user, password)

Data Objects

These classes generate Objects to represent the relational data inside the application.

Subscriber (id, name, addr, email)
mag (id, name, cost)
order (s, m[])

Data Access Logic

Following are the DAL functionalities identified. - I think the reason for such methods are obvious. The methods listed below have following signature <return-type> <method-name>(params)

• LoginManager
• bool AdminPwdCheck(uid, pwd)
• Magazine Data Manager
• MagList GetAllMagazines()
• Order Data Manager
• int SetMagsSubscribed(uid, maglist)
• maglist GetMagsSubscribed(uid)
• int TransactOrder(orderinfo)
• orderlist GetAllOrders()
• Subscriber Manager
• int CreateSubscriber(subscriberinfo)
• subscriberinfo GetSubscriberInfo()

Business Layer

You could have guessed it already, there would be not much to write in BL here.

• Magazine Manager
• list getAllMagazines()
• Order Manager
• bool OrderSubscription(o)
        { return TransactOrder(o)
           }
  list getAllOrders(name, pwd)
        {  if(pwd==getpwd(name))
                   return list getAllOrder();  }
• list getMagsSubscribed(sname, pwd)
         {   s=getSubscriber(sname)
              check(pwd valid)
              return getMagsSubscribed(sid)  }
• Subscriber Manager
• subscriberinfo GetSubscriberInfo(uid)

UI

I'm still in the process of finalizing the code details. anyway here's the UI design details. Will get back here with few of code snippets.

•      Registeration Form
  • New Registration
  • View my details
  • Admin Login
•       Confirmation Form
•       Summary Form

That's all with the design, let's take a walkthroug on some of code snippets...

             Implementing the database shouldn't be a problem. I used SQLServer 2005(and 2000). The data classes are to represent the tables of database in the application. classes in all the layer would utilise the data objects from these classes. The data classes are made serializable:

Classes in the DAL (Data Access Logic) layer will have code snippets to access data base and retrieve the data and represent in object form.

Ex:

catch(Exception ex)

{

return s;

}

In the above method, a special SQL Helper class is made use of, which opens up connection and facilitates execution of SQL commands sent to it. I'm making use of DataReaders, since the DAL objects and database are available in the same side of execution (server), there won't be significant performance loss. Further, DataSets can be used if the client wants to manipulate on the data. But here the specs need us only to display the data. (there is also facility to update the data directly, but I presume to keep it simple )

One good challenging task in design would be to create the GetAllOrders() method, which requires to package the subscribers, magazines subscribed and the order details in the format:

The LoginManager class will contain the code for manipulating on password using hashing. (soon...)

The Business layer wouldn't contain much code in this app, since much of th activities are only data transactions.