Nik's Technology Blog

Travels through programming, networks, and computers

Learning jQuery 1.3 - Book Review

My first exposure to jQuery was using other developer's plugins to create animation effects such as sliders, and accordion menus.
The highly refactored and compressed production code isn't the easiest to read and understand, especially if you want to alter the code to any great extent.
After reading a few tutorials, I thought I'd buy a book and get more involved with the jQuery library.

As an ASP.NET developer used to coding with intellisense, I was pleased that jQuery has been incorporated into Visual Studio to allow ease of developing.
I browsed through the jQuery books on Amazon and opted to buy "Learning JQuery 1.3" by Jonathon Chaffer and Karl Swedberg after reading the user reviews.

I've now read most of the book and can highly recommend it.  The book assumes the reader has good HTML, CSS knowledge as well as a familiarity with JavaScript and the DOM, but this enables the book to quickly move onto doing useful, everyday tasks with jQuery.

The first six chapters of the book explore the jQuery library in a series of tutorials and examples focusing on core jQuery components.  Chapters 7 to 9 look at real-world problems and show how jQuery can provide solutions to them, and the final two chapters cover using and developing jQuery plugins.

Web developers should be aware of web accessibility and SEO issues with using client-side scripting and it is good to see the book highlighting the concepts of progressive enhancement and graceful degradation where appropriate.

"the inherent danger in making certain functionality, visual appeal, or textual information available only to those with web browsers capable of (and enabled for) using JavaScript.  Important information should be accessible to all, not just people who happen to be using the right software." - Learning jQuery 1.3,  page 94

After a brief introduction into the world of jQuery, what it does and how it came about the book moves quickly on to selectors, which are a fundamental part of how jQuery selects element(s) from the DOM.  It also covers jQuery's chaining capability, which coming from other programming languages looks odd at the outset, but quickly proves to be a very powerful technique.

The authors then move on to talk about events.  What I particularly like about the way jQuery handles events is that the behavioural code can be cleanly separated away from the HTML mark-up without having to litter tags with onclick and onload attributes.

The examples show how to add functionality on top of your HTML by binding events to elements on the page, which when triggered cause jQuery to modify the HTML to bring the page to life.  Techniques are introduced by example, then slowly refactored and improved while introducing new jQuery methods along the way, which is a breeze to follow and learn.

The fourth chapter covers effects such as fading in and out and custom animations, and jumps straight in to cover a useful example of how text size can be increased on-the-fly for ease of reading.  The intro also mentions an important usability example of effects.

jQuery effects "can also provide important usability enhancements that help orient the user when there is some change on a page (especially common in AJAX applications)."- Learning jQuery 1.3,  page 67

Chapter 5 is all about DOM manipulation and covers jQuery's many insertion methods such as copying and cloning parts of the page, which it demonstrates with another useful example in the form of dynamically creating CSS styled pull quotes from a page of text used to attract a readers attention.

AJAX is the next topic, which interested me enough to create a little tool to load in an XML RSS feed and create a blog category list from the data.
The chapter covers the various options of loading partial data from the server including appending a snippet of HTML into the page, JSON, XML and how to choose which method is the most appropriate.

Table manipulation is next on the agenda and the book discusses how to sort table data preventing page refreshing using AJAX as well as client-side sorting, filtering and pagination.

Chapter 8 delves into forms, using progressive enhancement to improve their appearance and behaviour.  It also covers AJAX auto-completion as well as an in-depth look at shopping carts.

Shufflers and Rotators are next and the book starts out by building a headline news feed rotator which gets it's headlines from an RSS feed, typically used by blogs.  It also covers carousels, image shufflers and image enlargement.

Chapter 10 and 11 examine the plugin architecture of jQuery and demonstrate how to use plugins and build your own.  I successfully produced my first jQuery plugin from reading this book.  You can check out my tag cloud plugin and read about how I originally built it before turning it into a plugin that other developers can use.

No defining declaration found for implementing OnValidate(System.Data.Linq.ChangeAction)

If you happen to be getting an error message like the one below, then read on.

Error    1    No defining declaration found for implementing declaration of partial method 'mvcCMS.Models.WebPage.OnValidate(System.Data.Linq.ChangeAction)'    C:\mvcCMS\Models\WebPage.cs    28    22    mvcCMS


I'm using LINQ to SQL designer in Visual Studio to create a database schema and I'm using a partial class to extend the code generated by the designer.

In the example below I am using the pattern used by NerdDinner.com to add business rules/validation to the model classes LINQ to SQL built based on my database schema.

namespace mvcCMS.Models
{
    public partial class WebPage
    {
        public bool IsValid
        {
            get { return (GetRuleViolations().Count() == 0); }
        }
        public IEnumerable<RuleViolation> GetRuleViolations()
        {
            if (String.IsNullOrEmpty(Title))
                yield return new RuleViolation("Title is required", "Title");
            if (String.IsNullOrEmpty(Text))
                yield return new RuleViolation("Web copy is required", "Text");

            yield break;
        }
        partial void OnValidate(ChangeAction action)
        {
            if (!IsValid)
                throw new ApplicationException("Rule violations prevent saving");
        }
    }
}

Where OnValidate() is a partial method LINQ to SQL provides which enables us to be notified when the object is about to be persisted to the database, so we can check all our business rules have been met before the object is flushed to the database.

An empty OnValidate() method is part of the designer generated code for your data class located in the #region Extensibility Method Definitions and it seems that these Extensibility Method Definitions only get added to the designer code when your tables have primary keys.

When a table is dragged onto the Object Relational Designer in Visual Studio the classes that are generated will only implement INotifyPropertyChanging and INotifyPropertyChanged if your tables have primary keys.  If the classes don't implement these interfaces the code won't implement the OnValidate() method, and if the OnValidate() method doesn't exist your partial class won't compile.

The Solution

The solution is simple.  Add a primary key to your database table, delete the associated data class from the Object Relational Designer and then drag the database table from Server Explorer back onto the Object Relational Designer surface.

You should then find the designer generated code now implements INotifyPropertyChanging and INotifyPropertyChanged and the class contains a definition for OnValidate() in the #region Extensibility Method Definitions.  Your code should now compile.

Nik Makris is now Google Analytics Qualified!

I just passed the Google Analytics Individual Qualification (IQ) test with a score of 88%! I'm now officially qualified in Google Analytics!

Nik Makris is Google Analytics qualified

If you're interested in taking the test or simply want to learn more about Google Analytics then visit the Conversion University and brush up on your knowledge with the tutorials and presentations before taking the test.

I was actually quite surprised how much there is too Google Analytics and how powerful some of the features actually are, even though I've been using Google Analytics for years I learnt some really useful techniques and tricks.

More about the test

The test consists of 70 multiple choice questions and costs $50.  You are given 90 minutes to complete the test, and must achieve 75% to pass.  You are allowed to pause the test and continue later, but you must complete it within 5 days.  The whole test is completed online, and you will receive a PDF of your certificate on completion, which will look like the picture of mine above.  The qualification is valid for 18 monthsRead more frequently asked questions about the Google Analytics Individual Qualification FAQ.

Create a jQuery Tag Cloud from RSS XML Feed

I previously created a jQuery Blogger Template Category List Widget to retrieve blog categories from a Blogger.com RSS feed and create a list of links which click through to Blogger label pages.

I've now taken this code a step further and modified it to calculate the number of times each category/tag occurs enabling me to create a tag cloud from the data, like the one below.

 

Before I explain the code I wrote to make the tag cloud I'll go through the solution to a bug I found with the original categories code.

You may recall this snippet of code where I iterate through each post and then each category of each post, finally, when all the categories have been added to the array I sort them prior to de-duping them.

$.get('/blog/rss.xml', function(data) {
//Find each post
        $(data).find('item').each(function() {
//Get all the associated categories/tags for the post
            $($(this)).find('category').each(function() {
                categories[categories.length] = $(this).text();
            });
        });
        categories.sort();

I later refactored the code removing the $(data).find('item').each iteration which wasn't required since find('category') will find them all anyway.

I then discovered that the JavaScript .sort() function was case-sensitive which resulted in lower case categories being placed at the end of the list, causing problems when I de-dup them.

So the rewritten snippet of code became:

$.get('blog/rss.xml', function(data) {
     //Find each tag and add to an array
     $(data).find('category').each(function() {
         categories[categories.length] = $(this).text();
     });
     categories.sort(caseInsensitiveCompare);

where caseInsensitiveCompare refers to a JavaScript compare function:

function caseInsensitiveCompare(a, b) {
    var anew = a.toLowerCase();
    var bnew = b.toLowerCase();
    if (anew < bnew) return -1;
    if (anew > bnew) return 1;
    return 0;
}

Creating the Tag Cloud jQuery Code

I start off as before fetching the XML, adding all the categories/tags from the RSS feed to a JavaScript array, then sorting them.

But I needed a way to store, not only the tag name, but the number of times that tag is used on the blog (the number of times the category appears in the feed).  For this I decided to use a multi-dimensional array which would essentially store the data in a grid fashion e.g.

Tag Name Count
ASP.NET 5
Accessibility 2
Blogging 15
jQuery 2

 

The de-dup loop from my previous categories script now performs two jobs, it removes the tag duplicates and creates a count of each tag occurrence.

Once the multi-dimensional array has been populated, all that's left to do is iterate through the array creating the HTML necessary to build the tag cloud, followed by appending it to a DIV tag with an ID="bloggerCloud" on the page.

Note the calculation I perform to get the tags appearing a reasonable pixel size ((tagCount * 3) + 12).

$(document).ready(function() {
    var categories = new Array();
    var dedupedCategories = [];
    $.get('blog/rss.xml', function(data) {
        //Find each tag and add to an array
        $(data).find('category').each(function() {
            categories[categories.length] = $(this).text();
        });
        categories.sort(caseInsensitiveCompare);
        //Dedup tag list and create a multi-dimensional array to store 'tag' and 'tag count'
        var oldCategory = '';
        var x = 0;
        $(categories).each(function() {
            if (this.toString() != oldCategory) {
                //Create a new array to put inside the array row 
                dedupedCategories[x] = [];
                //Store the tag name first 
                dedupedCategories[x][0] = this.toString();
                //Start the tag count 
                dedupedCategories[x][1] = 1;
                x++;
            } else {
                //Increment tag count
                dedupedCategories[x - 1][1] = dedupedCategories[x - 1][1] + 1;
            }
            oldCategory = this.toString();
        });
        // Loop through all unique tags and write the cloud
        var cloudHtml = "";
        $(dedupedCategories).each(function(i) {
            cloudHtml += "<a href=\"/blog/labels/";
            cloudHtml += dedupedCategories[i][0] + ".html\"><span style=\"font-size:" + ((dedupedCategories[i][1] * 3) + 12) + "px;\">";
            cloudHtml += dedupedCategories[i][0] + "</span></a> \n";
        });
        $('#bloggerCloud').append(cloudHtml);
    });
    return false;
});

Since building this script I've now gone one step further and created a jQuery plug-in based on this code.  For more details and the source code see my jQuery Blogger.com Tag Cloud Plugin page.

Setting Up ASP.NET MVC with NUnit for Visual Studio 2008 Standard Edition &amp; Visual Web Developer Express 2008

I've just spent my lunch hour downloading and installing ASP.NET MVC.  I also downloaded the sample chapter from Professional ASP.NET MVC 1.0 (large PDF) which walks through the development of NerdDinner.com.  I began to create a test ASP.NET MVC project on Visual Studio 2008 Standard.

One of the main positives of ASP.NET MVC is that Test Driven Development is so much easier than with ASP.NET Webforms.

I soon realised when I created my first ASP.NET MVC project however that unless you have Visual Studio Professional or higher you don't get Visual Studio test Unit Framework, which means that to create a test project, you first need to install another testing framework such as NUnit, and configure Visual Studio or Visual Web Developer 2008 to use it.

This is an extract from the book Professional ASP.NET MVC 1.0:

Note: The Visual Studio Unit Test Framework is only available with Visual Studio 2008 Professional and
higher versions). If you are using VS 2008 Standard Edition or Visual Web Developer 2008 Express you
will need to download and install the NUnit, MBUnit or XUnit extensions for ASP.NET MVC in order for
this dialog to be shown. The dialog will not display if there aren't any test frameworks installed.

I already had NUnit installed, so I began my search for an NUnit extension for ASP.NET MVC, which I found here. Updated NUnit Templates for ASP.Net MVC 1.0 RTM

After running installNUnit.cmd which created the registry entries required by Visual Studio, you need to make sure the registry entries created point to the compressed templates.

Note: If you are using Visual Web Developer 2008, this might be all you need to do.  Click on File > New Project and check to see if "Test" appears under "Project types" on the left-hand menu in the dialogue box.  If not carry on reading.

Copy the NUnit test templates from the downloaded directory (in your chosen .NET language) MvcApplication.NUnit.Tests.zip to the following folder on your machine:

%Program Files%\Microsoft Visual Studio 9.0\Common7\IDE\ProjectTemplates\CSharp\Test

or here for VWD 2008:

%Program Files%\Microsoft Visual Studio 9.0\Common7\IDE\VWDExpress\ProjectTemplates\CSharp\Test

Then make sure the registry entry here:

HKEY_LOCAL_MACHINE\SOFTWARE\VisualStudio\9.0\MVC\TestProjectTemplates\NUnit\C#

or here for VWD 2008:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VWDExpress\9.0\MVC\TestProjectTemplates\NUnit\C#

Correctly points to the location of MvcApplication.NUnit.Tests.zip. e.g.

Path: CSharp\Test\

Template: MvcApplication.NUnit.Tests.zip

Then close all instances of Visual Studio and open up the command prompt and move to the following location:

C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE>

and run the following command:

> devenv /setup

Once this has completed, you should find that when you create an ASP.NET MVC project, you will now get another pop-up menu asking you if you wish to create a unit test project for your application using NUnit.

jQuery Blogger Template Category List Widget

Blogger is a hosted blogging service which allows you to publish your blog to your own URL and create your own custom HTML templates to match your website design. 
I have been using Blogger for this blog for several years, and have been trying to find a good way of displaying a list of categories on each blog page.

As yet I haven't found an official way of creating a category list using the Blogger mark-up code, so I decided to write my own widget to do the job for me.

When I say category list I mean a list of all the blog tags/labels in your blog, each linking to a page with posts categorised using that particular tag, just like the examples below.

Blog Categories

Because Blogger is a hosted blogging service you can't use a server-side language to create the category list for your HTML template, instead you must rely on client-side JavaScript.

Thankfully the Blogger service publishes XML files to your website along with the post, archive and category HTML pages.  These are in ATOM and RSS formats and are there primarily for syndication, but XML files are also fairly straight-forward to parse using most programming languages and contain all the category data we need to build a categories list.

I chose to use the jQuery library because it makes the process even easier.

The Blogger XML Format

From the Blogger ATOM XML snippet below you can see that each blog item can have multiple category nodes.  This means that the code must loop through each blog post, then loop through each category of each post to create our category list, but it also means that we will have duplicate categories, because more than one post can have the same category.

<item>
  <guid isPermaLink='false'></guid>
  <pubDate>Thu, 14 May 2009 18:30:00 +0000</pubDate>
  <atom:updated>2009-05-15T11:35:03.262+01:00</atom:updated>
  <category domain='http://www.blogger.com/atom/ns#'>C Sharp</category>
  <category domain='
http://www.blogger.com/atom/ns#'>ASP.NET</category>
  <category domain='
http://www.blogger.com/atom/ns#'>Visual Studio</category>
  <title>Language Interoperability in the .NET Framework</title>
  <atom:summary type='text'>.NET is a powerful framework which was built to allow cross-language support...</atom:summary>
  <link>http://www.nikmakris.com/blog/2009/05/language-interoperability-in-net.html</link>
  <author>Nik</author>
  <thr:total xmlns:thr='http://purl.org/syndication/thread/1.0'>0</thr:total>
</item>

The jQuery Code

The jQuery code is fairly easy to follow, but here is a quick explanation.  After the DOM is available for use, I create two JavaScript arrays, one to hold the categories and one to hold our de-duped category list.  Then I load in the Blogger RSS feed and iterate through each blog post adding each category to the categories array.
Once it reaches the end of the RSS feed, I need to sort the array into alphabetical order so that I can de-duplicate the categories list I just populated, which is what the next jQuery .each() function does.
All I have left to do is loop through the de-duped categories list, create the HTML link for each category and the append the HTML unordered list to the page.

$(document).ready(function() {
    var categories = new Array();
    var dedupedCategories = new Array();
    $.get('/blog/rss.xml', function(data) {
        //Find each post
        $(data).find('item').each(function() {
            //Get all the associated categories/tags for the post
            $($(this)).find('category').each(function() {
                categories[categories.length] = $(this).text();
            });
        });
        categories.sort();
        //Dedup category/tag list
        var oldCategory = '';
        $(categories).each(function() {
            if (this.toString() != oldCategory) {
                //Add new category/tag
                dedupedCategories[dedupedCategories.length] = this.toString();
            }
            oldCategory = this.toString();
        });
        // Loop through all unique categories/tags and write a link for each
        var html = "<h3>Categories</h3>";
        html += "<ul class=\"niceList\">";
        $(dedupedCategories).each(function() {
            html += "<li><a href=\"/blog/labels/";
            html += this.toString() + ".html\">";
            html += this.toString() + "</a></li>\n";

        });
        html += "</ul>";
        $('#bloggerCategories').append(html);
    });
    return false;
});

 

Update your Blogger Template HTML to Show Categories

The only HTML you need to add to your Blogger template is a call to jQuery, and this script in the head of your page, plus an empty HTML DIV tag, in the place where you want your categories list to appear.

<script type="text/javascript" src="/scripts/jquery.js"></script>
<script type="text/javascript" src="/scripts/blogcategories.js"></script>

<div id="bloggerCategories"></div>

You can see the script in action on my blog, or see this code rewritten to create a tag cloud.

An Introduction to Web Development and Design for Work Experience Students

We have a school student coming into our agency for work experience shortly, so I'm putting together a programme which will introduce him to the various areas of web development, such as HTML, CSS, client-side and server-side code, databases and XML.

It is going to be difficult to cover the various different skills involved in web development in a week, and without knowing what sort of web development knowledge the student already possesses it is hard to determine what can be achieved in such a short time.

However the main goal of work experience is to give the student a flavour of what is involved in the profession, to allow them to make an informed decision on whether such a career is for them.

I've structured the programme as follows:

Day 1 - Introduction to Web Design
Day 2 - Introduction to HTML and CSS
Day 3 - Understanding web servers, web browsers and HTTP and FTP
Day 4 - Introduction to server-side and client-side programming
Day 5 - Overview of databases and XML

Within each topic I have posed questions and tasks, which will require research and learning.  For each subject I have provided links to tutorials and online information.

I'm also aware that web development is very much a practical and creative skill, so I've also set a project which will run for the whole week and will allow him to put what he has learned into practice by building a simple personal portfolio website.

I have no idea whether I'm being too ambitious, but surely that will depend on the student's current knowledge and interest in the subject.  I think that it can easily be tailored to each student depending on their interests. 

I have uploaded a PDF of my programme entitled An Introduction to Web Development and Design for Work Experience Students and would appreciate any feedback.

Language Interoperability in the .NET Framework

.NET is a powerful framework which was built to allow cross-language support.  All .NET code is compiled to Intermediate Language (IL) whether you are developing in C#, VB.NET, J# or any other .NET language.  This means it is possible to build applications with modules written in different languages, because when the application is compiled it will all be compiled to a common language, IL.

This means a class written in one language can inherit from a class written in another language, or an object can directly call a method of another class written in another .NET language.  Visual Studio also allows you to step through all the different modules in the debugger.

To demonstrate the Language Interoperability in .NET, I'm going to call a VB.NET method from the code-behind page of a C# ASP.NET page.  This isn't something you would ordinarily want to do, but its an easy way to show the power of .NET.

In Visual Studio, right-click your website root in Solution Explorer and select add reference.  Scroll down the .NET tab until you find Microsoft.VisualBasic and click ok.

This will modify your Web.Config file by adding an assembly reference to Microsoft.VisualBasic to the assemblies list.

            <assemblies>
                <add assembly="System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
                <add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
                <add assembly="System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
                <add assembly="System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
                <add assembly="System.Web.Extensions.Design, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
                <add assembly="System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
                <add assembly="System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
                <add assembly="Microsoft.VisualBasic, Version=8.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/>
      </assemblies>

To use the VB.NET language within your C# webform you need to add a using Microsoft.VisualBasic; statement at the top of your code-behind page.

In my demo example below I am going to use the VB.NET MonthName method of DateAndTime to get the current month's name and display it on my page using a ASP.NET label control.  The bold code below is VB.NET interspersed with C#.

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Microsoft.VisualBasic;

public partial class language_interop : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        int month = DateTime.Today.Month;
        string monthName = DateAndTime.MonthName(month, false);
        labelMonthName.Text = monthName;
    }
}

Does your PC Keeping Forgetting the Date & Time?

Yesterday my aging desktop PC decided not to boot, and instead displayed this helpful error "CMOS Checksum Error".
In order to get it to boot into Windows I had to press Delete to go into the BIOS settings and change the configuration from "Halt on all errors" to "halt on no errors".  Upon saving the BIOS settings and restarting the error disappeared.

Sometimes though a PC with a dead CMOS battery will boot as normal but forget the date and time on each reboot.  This can lead to odd effects.  For instance I tried to logging into my webmail only to be told the SSL licence wasn't valid, not because it had expired but because my computer thought it was 2001!

CMOS Battery at Fault

Once I got into Windows I got a few "Windows has found new hardware" messages and my system clock had reverted to a day in 2001.
As soon as I saw my clock had forgotten the time and the date, all evidence pointed towards the CMOS battery being at fault.  Its funny how a simple little battery that most people don't even realise existed inside their PC can bring a computer to its knees.

Locating & Changing the CMOS Battery

In a desktop PC the CMOS battery is fairly straight forward to find.  They normally look like a large wrist watch battery, with CR2032 lithium batteries being the most common.  A simple search on eBay will find you a cheap replacement.  Just be careful removing and fitting anything on a motherboard, because any static electricity on your body could fry delicate computer chips.

CMOS battery on a desktop PC motherboard

On a laptop or notebook they are more difficult to find and generally more expensive.  On my Dell Inspiron you need to lift out the main battery and pull out a small flap to locate the CMOS battery.

Dell laptop battery housing

Location of CMOS battery in Dell Inspiron laptop

Dell Inspiron CMOS battery location

My Dell just so happens to take a 7.2V 15mAh Ni-MH CMOS battery, which again, performing a quick search on eBay will find you a replacement.

Fitting the new battery in either case is very straight forward.

Read more about Installing a CMOS Battery here.