ASP.NET was an easy choise for a server side code, but what about client side ?
The heavy viewstate, endless event handlers and infinity number of server side requests just to make the GUI  friendly – well, it just didn’t sound as a proper way to do it.

So, what do we have ?
.NET as a server side platform, but despite  all it’s powerful abilities it has nothing to do with client side. At the end of the day all those fancy control are just HTML and JavaScript.

JavaScript is still the engine that runs at the client side and it’s great, but we all know how many lines of code we have to write and time to spend to make it fast, modular and cross browser.

jQuery – it’s a fast and concise JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development.

Indeed, we can do a many things with jQuery and it realy simplify the coding, but what if we have to build a product list with complicated HMTL, complex logic and real time manipulation ?

As i mentioned before, ASP.NET and UpdatePanels are just to heavy and JavaScript is to long.

So, i did some research and find a couple of JavaScript Template Engines.
The first one i bumped in was jsRepeater. At first it seemed like a great solution but after a few tests i found all kinds of bugs related to the syntax conflicts with HTML and JavaScript.

After a few days of googling, tests and googling again i found the one and only –  jTemplates.
jTemplates is a template engine for JavaScript, wich is wraped in a jQuery Plugin.
The syntax is very simple and  intuitive. It’s support parameters, includes, if/else, loops, JavaScript functions and many other nice and usable features.

Let’s say we want to list all our products. What we have to do is to write the template (HTML), pass the data and we have a product list.

Look how easy this is. You just write HTML and werever you need to insert some data you put {$.T.P.ColumnName}.

So, how we use it ?
Just add some textarea to your page, give it some id, set it’s display style to none and write your template inside.

<textarea cols="0" rows ="0" style="display:none;" id="ProductListTemplate"><!--
{#foreach $T.Product as P}
	<div style=”float:left;width:150px;height:150px”>
		<div>{$T.P.Title}</div>
		<img src=”{$T.P.Url}” alt=”{$T.P.Title}” style=”width:10px;height:10px” />
		<hr />
		<div>Price : {$T.P.Price}$</div>
	</div>
{#/for}
--></textarea>

Add some empty container that will hold the result.

<div id="ProductListContainer"></div>

Execute setTemplateElement and execute processTemplate while passing the data into it as a parameter

$("#ProductListContainer").setTemplateElement("ProductListTemplate");
$("#ProductListContainer").processTemplate(data);

Easy, isn’t it ?
I must say that the above example is a simple one, but I’ve been using jTemplates to create complicated lists, grids, trees, popups and even an image editing web application. Use it, I’m sure you will love it.

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1. IE Memory Leak – jQuery Fix
2. Script as blocking element and dynamic script loading using document.write
3. Javascript function context, “apply” method and lost “this” object

Yesterday I had to write some app that reads files located on some remote computer.
As I knew already this ins’t such a good practice, because your code can just hang/freeze for seconds waiting for that UNC path to become available or just checking it’s existence.

Still, I had to provide some quick solution and “hoping for the best” wasn’t good enough.
So, this is what I came up with.

        public static T Limex<T>(Func<T> F, int Timeout, out bool Completed)
        {
            T result = default(T);
            Thread thread = new Thread(() => result = F());
            thread.Start();
            Completed = thread.Join(Timeout);
            if (!Completed) thread.Abort();
            return result;
        }

        // Overloaded method, for cases when we don't
        // need to know if the method was terminated
        public static T Limex<T>(Func<T> F, int Timeout)
        {
            bool Completed;
            return Limex(F, Timeout, out Completed);
        }

The usage is very simple, just pass any method (declared or anonymous) and the desired Timeout in milliseconds to the Limex.

Example :

bool Completed;
string Content = Limex(() => File.ReadAllText(@"\\unc\dir\file.ext")
                       ,100 // milliseconds
                       ,out Completed);

if (Completed)
   // Do something
else
  // Do something else

Comments and suggestions for improvement are welcome and will be gratefully appreciated

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Well, i needed something like that a few days ago and after Googling for couple of hours I ran across this this great library called HtmlAgilityPack.

Sure, you can do it by using C# WebBrowser control or MSHTML, but you will have to forget about performance or multithreading – it will eat all your memory and the CPU won’t know what’s hit it.

Now, back to the HtmlAgilityPack.
The usage is very simple, and the performance is great ( at least for my needs ).

Following is an example how we can find all images without an “alt” attribute, add it and resave the Html document.

            HtmlDocument HD = new HtmlDocument();
            HD.Load (@"e:\test.htm");
            var NoAltElements = HD.DocumentNode.SelectNodes("//img[not(@alt)]");
            if (NoAltElements != null)
            {
                foreach (HtmlNode HN in NoAltElements)
                {
                    HN.Attributes.Append("alt", "no alt image");
                }
            }

            HD.Save(@"e:\test.htm");

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2. jTemplates – jQuery Template Engine
3. C# string.Empty vs “”

        if (a-b) alert("it's true!");

And another one

What will be printed as result of running this script:

	for (var n=10; n; n-- )
	{
		document.write (n + ",");
	}

The answer for both questions relies on the same principle of what JavaScript engine will evaluate as true and what as false.

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3. Javascript function context, “apply” method and lost “this” object

    <script type="text/javascript">
        function doSomething(obj) {
            obj.style.color = '#cc0000';
        }
    </script>
    <a href="javascript:doSomething(this)">Link</a>

this keyword in his case was not A object as expected but window.
Having javascript:  in href attribute is like running JavaScript from address bar of your browser. It will run in window context.
Only if my friend was writing his code like this:

   ...
    <a onclick="doSomething(this)">Link</a>

it would work like charm.

But I never use javascript: at all in my markup. Why?
1. If you need text element that is clickable use span, any visual styling like text-decoration or cursor can be achieved using CSS.
2. If you don’t have actual link behind you shouldn’t use A tag. As far as I know it’s not good for SEO.
3. Javascript problems as i described above can arise
I would write the code above like this:

    ...
    <span style="text-decoration:underline;cursor:pointer;"
                 onclick="doSomething(this)">Link</span>

The only reason I know to use A for JavaScript triggers is to achieve hover effect without use of JavaScript.
If you know another reason why you should/shouldn’t use links as JavaScript triggers you’re welcome to comment.
After this post you can get an impression that I don’t like javascript: notation and you will be wrong,  actually there are very usefull tricks I use all the time:
1. Check some JS value on your page. Type javascript:alert(yourvariable) in the address bar and press enter.

You will get :

2. Or let’s say you have function somewhere on the page and you have to see it quick without searching through all your scripts. Or you wan’t to steal see how someone implemented something
Just type  javascript:alert(yourdesiredfunction) and voila:

UPD:
Just googled good page with JS best practices, it has Javascript: pseudoprotocol part that says almost exactly the same as my conclusions.
http://www.javascripttoolbox.com/bestpractices/

Related posts:

1. Javascript function context, “apply” method and lost “this” object
2. jTemplates – jQuery Template Engine
3. Script as blocking element and dynamic script loading using document.write

Will the following code compile and if yes what will be the result of it ?

static void Main(string[] args)
{
    int[] array = new[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

    Func<int, int> func = i => {
                          Console.Write(array[i]);
                          return i;
                     };

    var result = array.Where(e => e <= func(2)).ToArray ();
}

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<script type="text/javascript">
		function testThis(){
		  //who is "this"
		}
</script>

And now to the real example.

Let’s say you build a simple Javascript object:

<script type="text/javascript">
		var mathObj = {
			pi: 3.14,
			getCircumference : function(data) {
				alert(this.pi * 2 * data.radius);
			}
		}

		mathObj.getCircumference(10);
</script>

You have properties, you have functions, you can use this keyword to access properties of the object from its functions. Everyone is happy.
Now we want to add function that will get some server data using AJAX and run one of the functions our object has.
(To all who wondered what is $ stands for – I use JQuery framework in all my JS samples)

<script type="text/javascript">
		var mathObj = {
			pi: 3.14,
			getCircumference : function(data) {
				alert(this.pi * 2 * data.radius);
			},
			getRemoteCircumference: function(url) {
				$.getJSON(url, this.getCircumference);
			}
		}

		mathObj.getRemoteCircumference("RadiusData.js");
</script>

If we have {“radius”:5} in RadiusData.js file you would expect the result of getCircumference would be 31.4 but you will get NaN. Why is that? Because this keyword in this case will refer to some kind of object with request data returned by JQuery. What can you do?
Solution number one is to use your object name:

...
	getCircumference : function(data) {
		alert(mathObj.pi * 2 * data.radius);
	}
...

Ugly. You don’t have to return on object name in every function.
Solution number two is to use anonymous function and explicitly call your function:

....
	getRemoteCircumference: function(url) {
		$.getJSON(url, function(data){
			mathObj.getCircumference(data);
		});
	}
...

Good enough solution, but again I don’t like reusing object name…
And now to my favorite solution.

<script type="text/javascript">
   function getContextFunc(context, func) {
       return function() {
           func.apply(context, arguments);
       };
   }

   var mathObj = {
       pi: 3.14,
       getCircumference: function(data) {
           alert(this.pi * 2 * data.radius);
       },
       getRemoteCircumference: function(url) {
          $.getJSON(url, getContextFunc(this, this.getCircumference));
       }
   }

   mathObj.getRemoteCircumference("RadiusData.js");
</script>

Here apply function will come in handy. getContextFunc returns anonymous function that will run our original method in given context.
See some documentation

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A couple of days ago, I had to create some web application with a very rich client side UI.
It worked like a charm in Google Chrome, Firefox… but IE7, after few dozens of nyroModal popups it just went dead.

Most of the styles are gone, JavaScript functions began to throw exceptions till it just stoped working, decided it can’t tolerate this kind of abuse any more and closed it self without any warning.

The first thing i did is to open Performance Monitor and what I see… every nyroModal popup i open cost me about 5Mb, so after a few clicks my IE7 virtual memory was about 789Mb. Terrifying, isn’t it ?

I’ve searched a bit and found the source of this problem was in one (of many) memory leaks IE7 proudly has – cleaning memory for removed HTML elements.

And now the fix.

1). Open your jQuery.js and find the next lines of code

    jQuery.extend({
        cache: {},

and add new function “discardElement”

    jQuery.extend({
        cache: {},

        discardElement: function(element) {
            var jqGCID = 'jqGarbageCollector';
            var jqGC = document.getElementById(jqGCID);
            if (!jqGC) {
                jqGC = document.createElement('div');
                jqGC.id = jqGCID;
                jqGC.style.display = 'none';
                document.body.appendChild(jqGC);
            }

            // place the element to the Garbage Collector
            // and clear it's HTML contents
            jqGC.appendChild(element);
            jqGC.innerHTML = '';
        },

2). Find the next lines of code in the opened jquery.js

	remove: function( selector ) {
		if ( !selector || jQuery.filter( selector, [ this ] ).length ) {
			// Prevent memory leaks
			jQuery( "*", this ).add([this]).each(function(){
				jQuery.event.remove(this);
				jQuery.removeData(this);
			});
			if (this.parentNode)
				this.parentNode.removeChild( this );
		}
	},

and replace “this.parentNode.removeChild( this );”
with “jQuery.discardElement(this);”

	remove: function( selector ) {
		if ( !selector || jQuery.filter( selector, [ this ] ).length ) {
			// Prevent memory leaks
			jQuery( "*", this ).add([this]).each(function(){
				jQuery.event.remove(this);
				jQuery.removeData(this);
			});
			if (this.parentNode)
				// this.parentNode.removeChild( this );
				jQuery.discardElement(this);
		}
	},

That’s it, now you (and every plugin) can do $(‘element’).remove() without being worry IE will eat all of your memory.

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1. jTemplates – jQuery Template Engine
2. Javascript function context, “apply” method and lost “this” object
3. Javascript pseudo protocol (is EVIL)

static void Main(string[] args)
{
    for (byte b = byte.MinValue; b <= byte.MaxValue; b++)
        Console.Write(b);
}

// A little tip
// byte.MinValue = 0
// byte.MaxValue = 255

How many times the above statement will be executed ?

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AForge.NET is a C# framework designed for developers and researchers in the fields of Computer Vision and Artificial Intelligence – image processing, neural networks, genetic algorithms, machine learning, robotics, etc.

The framework is published under LGPL v3 license and comprised by the set of libraries and sample applications, which demonstrate their features:

• AForge.Imaging – library with image processing routines and filters
• AForge.Vision – computer vision library
• AForge.Neuro – neural networks computation library
• AForge.Genetic – evolution programming library
• AForge.MachineLearning – machine learning library
• AForge.Robotics – library providing support of some robotics kits
• AForge.Video – set of libraries for video processing

The framework is provided not only with different libraries and their sources, but with many sample applications, which demonstrate the use of this framework, and with documentation help files, which are provided in HTML Help format.

As you can see this framework contains varied libraries, but as for me i was especially interested in the image processing routines and filters.

Let’s see  the  CannyEdgeDetector in action.

using AForge.Imaging.Filters;

// Loading some file
using (Bitmap SampleImage = (Bitmap)Image.FromFile("test.jpg"))
{
    // We must convert it to grayscale because
    // the filter accepts 8 bpp grayscale images
    Grayscale GF = new Grayscale(0.2125, 0.7154, 0.0721);
    using (Bitmap GSampleImage = GF.Apply(SampleImage))
    {
        // Saving the grayscale image, so we could see it later
        GSampleImage.SaveAsJpeg("testBW.jpg", 100);

        // Detecting image edges and saving the result
        CannyEdgeDetector CED = new CannyEdgeDetector(0,70);
        CED.ApplyInPlace(GSampleImage);
        GSampleImage.SaveAsJpeg("testEDGED.jpg",100);
    }
}

// SaveAsJpeg is an extension method i wrote to be able to save
// Jpeg images with parametrized quality
// You can use Image.Save ("image.jpg", ImageFormat.Jpeg) instead

Now, let see the results ( click the image to see full size )

The result is great, and of course we can modify the threshold levels to gain even better results.
As for other filter and effects there are many of them in this library.
There are Noise generators, color correction filters, smoothing filters and more.

Sure, it’s no Photoshop, but i must say it’s very close to it.

Hope you will find this useful, I did.

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