Viktar Karpach Web Developer Blog about ASP.NET,C#,T-SQL,Javascript,CSS,Silverlight

Get and Set operators in Javascript

Sat, 04 Feb 2012 00:00:00 -0800

I am C# developer, hence I use C# properties a lot. However I just recently discovered that Javascript has properties as well. Get and Set operators supported by Firefox 2.0+, Safari 3.0+, Chrome, Opera 9.5+. However IE still doesn't support properties. May be Microsoft would introduce support in IE10, but so far no luck. Here is a little example of Get and Set declaration:

var obj = {

   get CustomProperty() {

     return 0;

},

   set CustomProperty(s) {

     alert ("It is readonly.");

};

Properties can be useful and scary at the same time. A simple variable assignment is not predictable anymore. For example with a little bit of work you can convert your AJAX calls to something like this:

ajax.url = "script.php";

alert(ajax.result);

YSlow and ASP.NET: 100 points "A" grade year 2012

Sun, 29 Jan 2012 00:00:00 -0800

Almost three years ago I wrote an original YSlow and ASP.NET: 100 points "A" grade is possible article. Since then I changed couple hosting providers, made numerous updates and converted my blog project to .NET 4.0. Today I decided to revise my blog to see if it still has 100 yslow points with final "A" grade.

First surprise, as of January 29, 2012, YSlow addon doesn't work in FireFox 9. However YSlow is now available for Google Chrome, Opera, Safari. It has bookmarket version and even command line version. I installed Google Chrome Yslow extension and began investigation. Right out of the box most of sections still had A grade. About a week ago I switched from Google App Engine "CDN" to true CDN Amazon CloudFront. Some files were not in CDN, so I had to take care of those. In general I highly recommend Amazon CloudFront. It is easy to setup and cost just a few bucks a month based on your traffic usage. Amazon CloudFront mimics your local file settings, so you need to make sure that you have compression, expire header and Etags taken care of. I use IIS7 compression instead of a compression module recommended by me in my previous article. Out of the box IIS7 compression doesn't work with AWS CloudFront, so you need to modify C:\Windows\System32\inetsrv\config\applicationHost.config file on your server to include following:

<serverRuntime enabled="true" frequentHitThreshold="1" frequentHitTimePeriod="00:00:20"/>

<httpCompression directory="%SystemDrive%\inetpub\temp\IIS Temporary Compressed Files" noCompressionForHttp10="False" noCompressionForProxies="False">

  <scheme name="gzip" dll="%Windir%\system32\inetsrv\gzip.dll" />

  <dynamicTypes>

    <add mimeType="text/*" enabled="true" />

    <add mimeType="message/*" enabled="true" />

    <add mimeType="application/x-javascript" enabled="true" />

    <add mimeType="*/*" enabled="false" />

  </dynamicTypes>

  <staticTypes>

    <add mimeType="text/*" enabled="true" />

    <add mimeType="message/*" enabled="true" />

    <add mimeType="application/javascript" enabled="true" />

    <add mimeType="*/*" enabled="false" />

  </staticTypes>

</httpCompression>

Also I modified my cache module to have ETags clean up:

public void Init(HttpApplication context)

...

    context.PostReleaseRequestState += new EventHandler(application_PostReleaseRequestState);

void application_PostReleaseRequestState(object sender, EventArgs e)

    HttpContext.Current.Response.Headers.Remove("Server");

    HttpContext.Current.Response.Headers.Remove("X-AspNet-Version");

    HttpContext.Current.Response.Headers.Remove("ETag");

YSlow added new section "Use Cookie-free Domains". My blog completely failed this one, since google analytics left cookies in top level karpach.com domain. I modified google analytics init script to have: _gaq.push(['_setDomainName', 'www.karpach.com']), so google cookies set for www.karpach.com instead of top level karpach.com. Then subdomain cdn.karpach.com, which points to Amazon CloudFront, became cookieless. Finally I am back to 100 YSlow points. Run Yslow on no externals version of karpach.com to see it yourself.

How to check if a javascript variable is undefined?

Thu, 12 Jan 2012 00:00:00 -0800

How to check if a javascript variable is undefined? This is actually a tricky question. There are three cases:

A variable is declared using var keyword, but were never assigned any value.
A variable is declared as function parameter, but when function were invoked parameter was not supplied.
A variable is never declared or assigned a value and you are trying to access it.

First two cases lead to undefined value of variable. Here is an example of first case:

var v; // Value not defined

if (v) {

    console.log("v=" + v);

else {

    console.log("v has undefined value");

v = "some value";

if (v) {

    console.log("v = " + v);

Output:
v has undefined value
v = some value

The second case is similar and you can use if statement as in above code or:

function Add(p1, p2) {

    p1 = p1 || 0; // set value to 0 if value is undefined

    p2 = p2 || 0; // set value to 0 if value is undefined

    return p1 + p2; // would always work

console.log(Add(1, 2));

console.log(Add(1));

console.log(Add());

Output:
3
1
0

The third case when a variable is never declared. If you try to use such variable you get exception. If statement or default value assignment won't help.

if(typeof neverDeclared == "undefined") {

    console.log("There is something really wrong!");

You would ask, what kind of sick people try to use a variable that was never declared or assigned a value? However I bet this is one of the most frequent javascript exceptions. Yes, simple variables are usually declared, but exception usually happens when you try to pass complex object with undeclared property. Javascript objects can be easily extended with additional properties and this comes at price of frequent undefined variable exceptions. Let me give you an example:

var obj = { FirstName: "Viktar", LastName: "Karpach" };

console.log(obj.FirstName);

console.log(obj.LastName);

console.log(obj.City); // Will give exception

var obj = { FirstName: "Viktar", LastName: "Karpach" };

obj.City = "Chicago";

console.log(obj.City); // Works!

if (typeof obj.State == "undefined") {

    console.log("State is undefined.");

Undefined variable exception very often happens when you try to consume objects received from third party API or from AJAX requests, always be careful what you consume from partially unreliable resource.

AutoHotkey DVDFab script for volume label conversion

Sun, 25 Dec 2011 00:00:00 -0800

From time to time I use free DVDFab HD Decrypter to rip rented movies, so I can watch them later using my Popcorn Hour A210 media streamer. DVDFab is kind enough to pull volume label from DVD disk. However this label has all uppercase letters and words are concatenated by underscores. For example:

THE_LONG_GOODBYE

I rename those labels to something like this: The Long Goodbye (1973), where year I lookup on IMDB web site. I don't like tedious repetitive tasks, so one day I decided to write a script for AutoHotkey to automate this process.

It is easy to replace underscores and correct letter case, but year should be retrieved from some kind of database. Google pointed me in a direction of IMDB API.

It might be a little bit challenging to do IMDB API access using just AutoHotkey script engine. Luckily AutoHotkey scripts can load dll libraries and with magic of COM.ahk and CLR.ahk you can load even .NET libraries. However those magic scripts can't properly execute .NET 3.5/4.0 libraries, so I had to use .NET 2.0. As you probably know .NET 2.0 doesn't have native support for JSON deserialization, so I had to use Newtonsoft.Json for this purpose. I also could use XML output from IMDB API, but I prefer to use JSON, since response is smaller in a size. Here is my code for .NET part of it:

public class Server

    public string GetMovieTitleWithYear(string volumeLablel)

        var request = WebRequest.Create(new Uri(string.Format("http://www.imdbapi.com/?t={0}",

            volumeLablel.Replace('_', '+'))));

        request.Method = "GET";

try

            var response = request.GetResponse();

            var responseStream = response.GetResponseStream();

            if (responseStream != null)

                var reader = new StreamReader(responseStream);

                var responseString = reader.ReadToEnd();

                var movie = JsonConvert.DeserializeObject<Movie>(responseString);

                if (movie != null && !string.IsNullOrEmpty(movie.Title))

                    return string.Format("{0} ({1})", movie.Title, movie.Year);

        catch

        return UppercaseWords(volumeLablel.Replace('_', ' ').ToLower());

    static string UppercaseWords(string value)

        char[] array = value.ToCharArray();

        // Handle the first letter in the string.

        if (array.Length >= 1)

            if (char.IsLower(array[0]))

                array[0] = char.ToUpper(array[0]);

        // Scan through the letters, checking for spaces.

        // ... Uppercase the lowercase letters following spaces.

        for (int i = 1; i < array.Length; i++)

            if (array[i - 1] == ' ')

                if (char.IsLower(array[i]))

                    array[i] = char.ToUpper(array[i]);

        return new string(array);

Then using JSON 2 C# Service you get following:

public class Movie

    public string Title { get; set; }

    public int Year { get; set; }

    public string Rated { get; set; }

    public string Released { get; set; }

    public string Genre { get; set; }

    public string Director { get; set; }

    public string Writer { get; set; }

    public string Actors { get; set; }

    public string Plot { get; set; }

    public string Poster { get; set; }

    public string Runtime { get; set; }

    public float Rating { get; set; }

    public int Votes { get; set; }

    public string ID { get; set; }

    public string Response { get; set; }

Library is ready. Lets plug it into AutoHotkey:

#include c:\Program Files (x86)\Autohotkey\Extras\Scripts\CLR.ahk
#include c:\Program Files (x86)\Autohotkey\Extras\Scripts\COM.ahk

RemoveToolTip:
SetTimer, RemoveToolTip, Off
ToolTip
return

#IfWinActive ahk_class QWidget
~Lbutton::
MouseGetPos, xpos,ypos
if (xpos>306 and ypos>474 and xpos<605 and ypos<495)
{
	ToolTip, Double click in text box below`nto get IMDB title and year,305,430
	SetTimer, RemoveToolTip, 5000
}
If (A_PriorHotKey = A_ThisHotKey and A_TimeSincePriorHotkey < 500) 
{
    CLR_Start()
	imdb := CLR_LoadLibrary("c:\Program Files (x86)\Autohotkey\Extras\Scripts\Karpach.IMDB.dll")
	;Type names must be fully qualified.
	server:= CLR_CreateObject(imdb,"Karpach.IMDB.Server")
	Send ^a
	Sleep 100
	clipboard =   
	Send ^c
	ClipWait
	title:=COM_Invoke(server,"GetMovieTitleWithYear",clipboard)
	COM_Release(imdb)
	COM_Release(server)
	clipboard = %title%
	Send ^v
	return  
}
return

#IfWinActive

Now whenever you double click in volume label text box content would be converted into proper movie title.

AutoHotkey scripts and DLLs

IMDB API .NET library source code

Simple factory pattern based on interfaces

Mon, 05 Sep 2011 00:00:00 -0700

The main purpose of factory design patterns is to separate object creation process from current implementation context. During coding you use factory to create objects. Based on incoming parameters factory decides which object to create. You don't know exact type of the object. Usually you know either base abstract class type that created object was inherited from or interface that created object is implementing. Based on this knowledge you can use object (call abstract class methods or interface methods). I found a lot of factories examples with abstract class connection, but none with interface connection. However interface connection is most common in commercial factory design pattern implementations. Many developers use Unity Framework or Castle Project (example of connection based on interface). Below I'll show how to implement factory with interface connection like it is done in Unity Framework or Castle Project.

Lets build animal fabric, which would create dogs and cats objects. Let's define ICat and IDog interfaces.

public interface ICat

    string Meow();

public interface IDog

    string Bark();

    string Sit();

Now, lets define some Dog and Cat classes that implement ICat and IDog interfaces respectevly.

public class Cat:ICat

    public string Meow()

        return "Meow meow meow ...";

public class Dog: IDog

    public string Bark()

        return "Woof woof woof ...";

    public string Sit()

        return "I am sitting.";

Now lets create factory:

public class DefaultFactory

    public static T Create<T>()

        if (typeof(T) == typeof(IDog))

            return (T)(IDog)new Dog();

        else

            if (typeof(T) == typeof(ICat))

                return (T)(ICat)new Cat();

            else

                throw new NotImplementedException(String.Format("Creation of {0} interface is not supported yet.", typeof(T)));

And here how you can use it:

IDog dog = DefaultFactory.Create<IDog>();

ICat cat = DefaultFactory.Create<ICat>();

Console.WriteLine(dog.Bark());

Console.WriteLine(dog.Sit());

Console.WriteLine(cat.Meow());

Output:

Woof woof woof ...
I am sitting.
Meow meow meow ...

Source code for sample project above.

Video Links in a New Media Player Window

Thu, 12 May 2011 00:00:00 -0700

Google Chrome extension popups Youtube, IMDB, Vimeo and Twitvid links in new window with just a video player. Video player window can be resized to scale video. Works with online chats that post links dynamically, for example CampFire from 37 Signals.

Each video gets its own window, so you can open as many videos as you like. Cntrl-Click to open link regular way.

Please leave comments and suggestions.

Install Google Chrome Extension

After you install extension try to click on sample links below:

How to find column usage in stored procedure?

Sun, 08 May 2011 00:00:00 -0700

Sometimes you want to rename or delete column from a table in MS SQL Server. How to find column name dependency usage in MS SQL Server? There is no clean way of doing this. In management studio you can right click on object and select "View Dependency", but this would show only object dependency. So you need to write some T-SQL code in order to find dependency. Lets say we need to find dependecy of Title column from the Article table.

SELECT DISTINCT so.name

FROM sys.syscomments sc

INNER JOIN sys.objects so on sc.id=so.object_id

WHERE sc.text LIKE '%Title%'

How to sort lists using lambda expressions?

Wed, 26 Jan 2011 00:00:00 -0800

Usually I get needed information from SQL server and then do further processing on server side of my web application. Lets say I have a grid of users. Client can sort it by first name or last name, ascending or descending. It is too much typing to create four comparers for Sort method. Luckily you can use lambda expressions. Below is full example:

class Program

{

static void Main(string[] args)

{

List<User> users = new List<User>(new [] {

new User {FirstName = "Viktar",LastName = "Karpach"},

new User {FirstName = "Vasya",LastName = "Pupkin"},

new User {FirstName = "Joe",LastName = "Doe"},

new User {FirstName = "Jane",LastName = "Doe"}

});

Console.WriteLine("Assceding order sorted by first name");

users.Sort((u1, u2) => string.Compare(u1.FirstName, u2.FirstName, false));

PrintList(users);

Console.WriteLine("Descending order sorted by first name");

users.Sort((u1, u2) => string.Compare(u2.FirstName, u1.FirstName, false));

PrintList(users);

Console.WriteLine("Assceding order sorted by last name");

users.Sort((u1, u2) => string.Compare(u1.LastName, u2.LastName, false));

PrintList(users);

Console.WriteLine("Descending order sorted by last name");

users.Sort((u1, u2) => string.Compare(u2.LastName, u1.LastName, false));

PrintList(users);

Console.ReadLine();

}

static void PrintList(List<User> users)

{

foreach (var user in users)

{

Console.WriteLine("{0} {1}",user.FirstName,user.LastName);

}

public class User

{

public string FirstName { get; set; }

public string LastName { get; set; }

}

Results:

Assceding order sorted by first name

Jane Doe
Joe Doe
Vasya Pupkin
Viktar Karpach

Descending order sorted by first name

Viktar Karpach
Vasya Pupkin
Joe Doe
Jane Doe

Assceding order sorted by last name

Joe Doe
Jane Doe
Viktar Karpach
Vasya Pupkin

Descending order sorted by last name

Vasya Pupkin
Viktar Karpach
Joe Doe
Jane Doe

How to enable intellisence for FireFox console command?

Sat, 25 Dec 2010 00:00:00 -0800

Almost every web developer knows about FireBug console window, but I still see some developers who uses javascript alert command for tracing javascript output. You can actually write to FireBug console window using console command from your javascript. However since this is not a standard javascript command, Visual Studio doesn't have itellisence for it. So, here is vsdoc file, which enables intellisence for console command.

P.S.
Thanks to David Murdoch for creating it.

Null coalescing operator for JavaScript

Sun, 12 Dec 2010 00:00:00 -0800

Very often in javascript some function parameters are optional. So, code like this become needed:

if (typeof something == "undefined")

alert("something is undefined");

However, there is a better, slicker solution. This is a null coalescing operator in javascript "terms":

function DoSomething(element)

{

element = element || document.body;

}

function DoSomething(index)

{

index = index || 0;

}

In example above element variable gets value of document.body if null (undefined). Similarly index variable gets 0 value if undefined or null.

How you can use HTML5 Web Forms 2.0?

Sat, 02 Oct 2010 00:00:00 -0700

Webforms 2.0 (HTML5) introduces many useful features. Things that usually done using javascript now are build in a browser.

1. Textbox watermark. Supported by FireFox 3.7+, Safari 4.0+, Chrome 4.0+, iPhone 4.0+

2. Default form element autofocus. See Google search as an example. Supported by Safari 4.0+,Chrome 3.0+, Opera 10.0+

<label for="txtSearch">Search:</label>

3. Form / input autocomplete is partially implemented by all current browsers.

If you ever tried to implement custom autocomplete, just like google has, then you know, first of all you need to turn off browser's autocomplete.

So, some browsers support new attributes, some doesn't. Is there an easy way to find out? Here is a little snippet that can help you to find if certain attribute is supported.

String.prototype.hasProperty = function(property)

{

return property in document.createElement(this);

};

if (!'input'.hasProperty('autofocus'))

{

// Custom implementation for autofocus

}

</script>

How to regenerate T4 templates from command prompt?

Fri, 06 Aug 2010 00:00:00 -0700

I am using T4 templates for web.config templating for different environments (development, production). You can regenerate templates from Visual Studio, but what if you want to regenerate all of them from console. It is very useful if you had some mass change in all your web.tt (in different projects) and now need to regenerate corresponding web.config-s.

Here is a little batch script that can help you to do this:

@echo off
SETLOCAL ENABLEDELAYEDEXPANSION

:: set the working dir (default to current dir)
set wdir=%cd%
if not (%1)==() set wdir=%1

echo executing transform_all from %wdir%
:: create a list of all the T4 templates in the working dir
dir %wdir%\web*.tt /b /s > t4list.txt

echo the following T4 templates will be transformed:
type t4list.txt

:: transform all the templates
for /f %%d in (t4list.txt) do (
  set configfile=%%d
  set configfile=!configfile:~0,-3!.config
  echo:  \--^> !configfile!
  "%CommonProgramFiles%\Microsoft Shared\TextTemplating\1.2\TextTransform.exe" -out !configfile! %%d
)

echo transformation complete

How to control your iPhone remotely?

Fri, 09 Jul 2010 00:00:00 -0700

Remote control of your iPhone might be very useful for testing iPhone friendly web sites. You can use emulators for this purpose. Blackboud iPhone Browser Simulator is not bad, but still this is not a real iPhone browser.

First of all you iPhone needs to be jailbroken. Then you need to install VNC Server for iPhone. Just search for Veency in Cydia, it is free.

On you desktop you need VNC Viewer. There are bunch of them, but I use UltraVNC since it is free. Then you can connect to your iPhone over Wi-Fi, but you can do it thru USB too.

For USB connection you need to install python interpreter and usbmuxd. From usbmuxd we need only python client part. Run connect.bat, which has following line inside:

c:\python26\python.exe tcprelay.py 5900

And then you can connect to your iPhone using 127.0.0.1 address.

How to fix ViewStateException Invalid ViewState?

Wed, 23 Jun 2010 00:00:00 -0700

Usually you don't see Invalid ViewState exception unless you implement some kind of ASP.NET error logger in Global.asax.

Error usually states something like this:

Exception: System.Web.HttpException: The state information is invalid for this page and might be corrupted. ---> System.Web.UI.ViewStateException: Invalid viewstate.

Those errors are usually generated by some automatic submission form engines. Comments and contact forms are mostly effected by this exception. End user never sees those errors, so invalid viewstate errors don't have any value for your error logger. Let's bypass them:

if (ex is HttpException && ex.InnerException is ViewStateException)

    _app.Response.Redirect(_app.Request.Url.AbsoluteUri)

    return

See my error logger article for further details.

XRefresh alternative solution

Mon, 31 May 2010 00:00:00 -0700

I am using two monitors for a web development for the past 4 years. Usually I have website that I am working on a left monitor and my Visual Studio on a right monitor. Usually I do change in Visual Studio then press Shift-F6 (in case of code change) or just Ctrl-S (to save). After that I grab a mouse, move cursor to browser on left monitor click and then F5 for refresh. If you do a little CSS tricks it is to much repetitive movements.

About two years ago I discovered XRefresh. I mentioned it in my ASP.NET development tips article. First I was really excited. It is excellent tool for html and CSS markup tweaking. But if you do a lot of code changes and need to recompile your project more often then markup tweaking then it might not be a best tool for you. XRefresh watches files. If file changes then it refreshes browser. Now imagine if you compile big project and compilation takes 15 sec. XRefresh would notice dll change and would try to refresh browser. However compilation is not done yet and some dll-s are locked. So, XRefresh most likely not going to work for Shift-F6 scenario (recompilation of project). This was quite annoying as you can imagine, so I thought there must be some way to come up with a solution. We may have read all the hardware and O2 uk broadband reviews possible, but if you're screen is not refreshing properly that can be very inconvenient. I am not one to sit around when presented with an inconvenient situation however.

So, I found XRefresh alternative solution. I wrote a Visual Studio macros. You can hook up to OnBuildDone event. Then find Firefox process. Move focus to Firefox window and send F5 keystroke to it. Macros below still needs some polishing, but you can get an idea:

Private Sub BuildEvents_OnBuildDone(ByVal Scope As EnvDTE.vsBuildScope, _ 
 ByVal Action As EnvDTE.vsBuildAction) Handles BuildEvents.OnBuildDone

    Dim projects As Object() = DTE.ActiveSolutionProjects

    If projects.Length > 0 Then

        If CType(projects(0), Project).ExtenderNames.Length Then

            If CType(projects(0), Project).ExtenderNames(0) = "WebApplication" Then

                Dim proc As System.Diagnostics.Process() = _
                          System.Diagnostics.Process.GetProcessesByName("firefox")

                For i As Integer = 0 To proc.Length - 1

                    If proc(i).MainWindowHandle <> 0 Then

                        SetForegroundWindow(New HandleRef(Nothing, proc(i).MainWindowHandle))

                        System.Windows.Forms.SendKeys.SendWait("{F5}")

                    End If

                Next

            End If

        End If

    End If

End Sub

I am open for discussions and any suggestions.