.Net Interview Questions, Resources, Tips & Tricks.

WebMatrix - Microsoft new IDE (Free Tool)

2010-07-15T01:59:00.001-04:00

Have a look at WebMatrix a new IDE for Web Development. (Simplifies Web development)
http://www.microsoft.com/web/webmatrix

Introduction and First application.
http://weblogs.asp.net/scottgu/archive/2010/07/06/introducing-webmatrix.aspx

Simple IDE for website development uses inbuilt lightweight file based database and the new cshtml is amazing (similar to Coldfusion).
- SQL Server Compact Edition
- Cshtml (ASP.NET Razor)
- IIS Express with all required developer features.
- Web Server
- Open source application gallery (Web Apps)

Microsoft Jobs

2010-07-15T01:25:00.003-04:00

1. SR Software Development Engineer

SQL 2005/2008
.NET Framework 3.5/4.0
ASP.NET/ASP/C#
WCF/WPF/WF/Silverlight
SharePoint 2007/2010

Apply Now: http://www.jobthread.com/jt/jobs/widget_click.php?id=85794d&job_id=541131

2. Software Development Engineer (SDE)

and formulate recommendations clearly. Technical horsepower and critical thinking are required.
6+ years of software development experience with C#, Silverlight, .Net programming, WCF Web services , SQL and VSTF 2008\2010.

Apply Now: http://www.jobthread.com/jt/jobs/widget_click.php?id=85794d&job_id=541135

What is Method Hiding?

2010-04-09T14:21:00.001-04:00

Method hiding is to hide/mask method in base class by creating a similar function in derived class and by using new keyword in the derived class.
Unlike Method overriding, When we refer base class object created by casting derived class object a method in base class will be called.
Also we can change the return type while masking the base class method.
Using new keyword is not compulsory, however a warning will be displayed if we wont specify new keyword while masking.

Example:

Base Class:
--------------
public class BaseClass
{
public virtual void Method1()
{
Print("Base Class Method");
}
}

Derived class
---------------
public class DerivedClass: BaseClass
{
public override void Method1()
{
Print("Derived Class Method");
}
}

Usage
-------------------
public class Sample
{
public void TestMethod()
{
DerivedClass objDC = new DerivedClass();
objDC.Method1();
BaseClass objBC = (BaseClass)objDC;
objDC.Method1();
}
}
Result
-----------------------------------
Derived Class Method
Base Class Method

Difference Between Function Overloading and Overriding ?

2010-04-09T14:20:00.002-04:00

Overloading means having functions with the same name but with different signature.Signature includes method name and Parameters. These functions can be part of base class or derived class.

Whereas Overriding means changing the functionality of a method without changing the signature. We can override a funtion in base class by creating a similar function in derived class and by use virtual/override keywords.

Base class method has to be marked with virtual keyword and we can override it in derived class using override keyword.

Derived class method will completly overrides base class method i.e when we refer base class object created by casting derived class object a method in derived class will be called.

Example:

Base Class:
-------------------------------
public class BaseClass
{
public virtual void Method1()
{
Print("Base Class Method");
}
}

Derived class
---------------
public class DerivedClass: BaseClass
{
public override void Method1()
{
Print("Derived Class Method");
}
}

Usage
--------------------------
public class Sample
{
public void TestMethod()
{
DerivedClass objDC = new DerivedClass();
objDC.Method1();
BaseClass objBC = (BaseClass)objDC;
objDC.Method1();
}
}

Result
---------------------
Derived Class Method
Derived Class Method

What is the difference between int.Parse and int.TryParse methods?

2010-04-09T14:20:00.001-04:00

int.Parse is a simple method used to convert string to integer. It throws exception when null or invalid input is provided. Hence it is slow.

int.TryParse does not thow any exception instead we must describe second parameter as out parameter which holds result. And it returns boolean value representing success or failure.

What is the difference between System.Text.StringBuilder and System.String?

2010-04-09T14:19:00.001-04:00

String is immutable and string builder is mutable.
String is useful as some costly operations for copying and comparing can be omitted making program simple.

However, making an object immutable is usually inappropriate if the object contains a large amount of changeable data.

So String is not suggested to hold huge data as replacements or concatinations will be costly and time consuming.

Copying is simple using reference. Whereas reference copying technique (Copying data without pointing to the same reference) is difficult in case of StringBuilder.

String will allocate only what is needed. When we concatinate strings, it sums up the length of all and creates buffer to fit that.

Whereas string builder allocates capacity of 16 initially and increases capacity in the multiples of 2.

What do you mean by String objects are immutable?

2010-04-09T14:18:00.000-04:00

String objects are immutable as its state cannot be modified once created.
Every time when we perform any operation like copy, replace, case conversion or when we pass a string object as a parameter to a method a new object will be created.

Example:

String s = "ABC";
s.Replace("A","X");

Here Replace() method will not change data that s contains, instead a new string object is created to hold data "XBC" and the reference to this object is returned by Replace() method.

So in order to point s to this object we need to write below line.
s = s.Replace("A","X");

Broken Authentication and Session Management

2010-04-08T14:20:00.000-04:00

As HTTP is a state less protocol and we need to maintain the information to authenticate the users. Below are the precaution the we need to follow

We can use one of the below suggested methods for authentication

Forms Authentication
Windows Authentication
Passport

Change Password Controls

Always we need to ask for old password and new password.
If we are sending reset password links to users email we need to re-authenticate the user when he tries to change his email address.

All passwords should be stored in database in encrypted format. Use System.Security.Cryptography in .NET

Symmetric Algorithms	Asymmetric Algorithms	Hash Algorithms
DES (Data Encryption Standard)	DSA (Digital Signature Algorithm)	HMAC SHA1 (Hash-based Message Authentication Code using the SHA1 hash algorithm)
TripleDES (Triple Data Encryption Standard)	RSA	MAC Triple DES (Message Authentication Code using Triple DES)
Rijndael		MD5
RC2		SHA1, SHA256, SHA384, SHA512 (Secure Hash Algorithm using various hash sizes)

Source: http://msdn.microsoft.com/en-us/library/aa302378.aspx

Protection during transmit:

In order to protect the passwords or transaction session Ids it is suggested to use SSL. Try to use SSL for all login pages so that credentials will be protected.
SessionIds should not be transferred in querystrings.
Session Ids should be long and complex to decode.
Session Id can be formed by encrypting it along with IP Address, so that we can check for the IP Address and compare it in server side.
Session IDs must be changed when switching to SSL, authenticating, or other major transitions. Session IDs chosen by a user should never be accepted.

We need to make sure that session is timed out when user clicks on logout button.
Application timeout should be set properly so that sessions are abandoned when user closes the browser instead of clicking on logout.

SharePoint Architecture Diagram

2010-03-20T07:22:00.003-04:00

SharePoint Coding Practices

2010-03-20T07:14:00.002-04:00

Memory used by some SharePoint objects, primarily the SPSite and SPWeb objects, cannot be automatically freed up by the runtime. This can cause problems, since every such object may account for 1-2 MB. Also, these objects are often created automatically and more or less intuitively. Therefore, we need to always manually dispose some of the SharePoint objects.

For most objects, this can be done by

· Calling Dispose(): This works in most scenarios and are considered best practice. Ideally, this should be put within a “final” clause so we are sure it is always run even if preceding code fails. If possible, use “using” instead of calling Dispose()!

· Declaring the disposable object with “using”: This is also considered best practice. The compiler converts this into a try-catch-finally clause and puts a Dispose() call in the finally clause. “Using” is also best practice just like calling Dispose(), but because of the automatic creation of a “finally” clause, and because it makes the code slightly more readable, “using” is preferred over calling Dispose()! However, “using” is not applicable in all cases, such as when looping through a SPSiteCollection or SPWebCollection. The examples throughout this document use “using” whenever possible.

· Calling Close(): This May work fine for many objects, but it is not recommended in any scenario where Dispose() or “using” is available.

Methods and properties

The following declarations, methods and properties create or returns new objects which must be disposed before they leave their scope to avoid leaking memory. Note that when accessing properties (RootWeb, Parent, etc), new objects are automatically created.

Method or property:	What to dispose?
new SPSite()	The returned SPSite
new SPGlobalAdmin()	The returned SPGlobalAdmin
new SPLimitedWebPartManager()	The returned SPLimitedWebPartManager
SPSite.OpenWeb()	The returned SPWeb
SPSite.SelfServiceCreateSite()	The returned SPSite
SPList.ParentWeb	The returned SPWeb
SPWeb.ParentWeb	The returned SPWeb
SPSite.RootWeb	The returned SPWeb
WebPartPage.RootWeb	The returned SPWeb

The following properties and methods returns references to existing objects, and must not be disposed.

Method or property:
SPControl.GetContextSite()
SPControl.GetContextWeb()
SPContext.Current.Site
SPContext.Current.Web
SPContext.Site
SPContext.Web

The lists above are far from complete; When any SharePoint object is accessed or returned, consideration should always be taken to whether the returned object should be disposed or not.

Warning: New objects are created even when not storing the reference to them. In the lines below, new objects are created, which must - but cannot - be disposed:

str = site.OpenWeb().Title; // do not do this!

str = site.RootWeb.url; // do not do this!

Warning: Accessing RootWeb or ParentWeb on any of the SPContext subobjects, still requires RootWeb/ParentWeb to be disposed. For example,

If you access: SPContext.Current.Site.RootWeb

You should dispose: SPContext.Current.Site.RootWeb

But should NOT dispose: SPContext.Current.Site

It is safe to dispose an object which has already been disposed.

Bad practice (leaks!)

Best practice (no leaks)

Public void anyMethod() {

SPSite site = new SPSite();

SPWeb web = site.OpenWeb();

// ...

} // both web and site leaked!

Public void anyMethod() {

using (SPSite site = new SPSite()) {

using (SPWeb web = site.OpenWeb()) {

// ...

}

Public void anyMethod() {

// this SPSite leaks:

using (SPWeb web = new SPSite(...).OpenWeb(...)) {

// ...

}

Public void anyMethod() {

using (SPSite site = new SPSite(...)) {

using (SPWeb web = site.OpenWeb(...)) {

// ...

}

public void anyMethod() {

SPSite site;

while (...) {

site = new SPSite();

// ...

}

site.Dispose();

// every object except the last one leaked!

}

public void anyMethod() {

SPSite site;

while (...) {

site = new SPSite();

// ...

site.Dispose();

}

public void anyMethod() {

using (SPSite site = SPContext.Current.Site) {

// ...

} // oups, we disposed a shared object!!

}

public void anyMethod() {

SPSite site = SPContext.Current.Site;

// ...

}

public void anyMethod() {

using (SPSite site = new SPSite()) {

site.RootWeb.Url = “New Title”;

}

} // site disposed properly, but ParentWeb leaked!

public void anyMethod() {

using (SPSite site = new SPSite()) {

using (SPWeb rootWeb = site.RootWeb) {

rootWeb.title = “New Title”;

}

public string anyMethod(SPListItem item) {

// ...

return item.ParentList.ParentWeb.Url;

} // ParentWeb leaked!

public string anyMethod(SPListItem item) {

string returnValue;

using (SPWeb parentWeb = item.ParentList.ParentWeb) {

returnValue = parentWeb.Url;

}

return returnValue;

}

public string anyMethod() {

return SPContext.Current.Site.RootWeb.Url;

}

public string anyMethod() {

string returnValue;

using (SPWeb parentWeb = SPContext.Current.Site.RootWeb) {

returnValue = parentWeb.Url;

}

return returnValue;

}

Collections

Many methods and properties has types of SPSiteCollection or SPWebCollection, such as:

· SPSite.AllWebs (Field: SPWebCollection)

· SPWeb.Webs (Field: SPWebCollection)

· SPWeb.GetSubwebsForCurrentUser (Return value: SPWebCollection)

It is easy to believe those returned collections contain existing SPSite and SPWeb objects, but these are actually created upon access on individual items. This must be remembered when using for each to loop through the collection, accessing a specific index, or adding an item to the collection – in all cases, the accessed or added object must be disposed.

Bad practice (leaks!)

Best practice (no leaks)

public void anyMethod(SPWeb web) {

foreach (SPWeb web in web.GetSubWebsForCurrentUser(...)) {

// ...

}

} // every web leaked!

public void anyMethod(SPWeb web) {

foreach (SPWeb web in site.GetSubWebsForCurrentUser(...)) {

// ....

web.Dispose(); // we can’t use “using” here

}

public void anyMethod() {

SPSiteCollection siteColl = ...;

siteColl[0].Title = “New Title”;

} // siteColl [0] was created but never disposed!

public void anyMethod() {

SPSiteCollection siteColl = ...;

using (SPSite web = siteColl[0]) {

web.Title = “New Title”;

}

public void anyMethod() {

SPSite site = SPControl.GetContextSite(...);

site.AllWebs.Add( ... );

}

public void anyMethod() {

SPSite site = SPControl.GetContextSite(...);

using(SPWeb web = site.AllWebs.Add( ... )) {

// ...

}

Special cases

There are a number of members and methods which will create new objects, whos disposal must be made in an unusual way. Here is a list which should cover most of them:

Type	Method/field	Requires
SPLimitedWebPartManager	(Any use)	(object).web.Dispose();
SPList	BreakRoleInheritance()	(object).ParentWeb.Dispose();
SPWeb	LockIssue	(object).RootWeb.Dispose();
SPWeb	Owner	(object).RootWeb.Dispose();
SPWeb	SecondaryContact	(object).RootWeb.Dispose();
PublishingWeb	GetPublishingWebs()	Each accessed item must be disposed by calling its Close().
PublishingWebCollection	Add()	Returned object must be disposed by calling Close().

MS Excel like Ceiling function in c#.

2010-02-26T05:33:00.000-05:00

- EXcel Ceiling function returns a number rounded up based on a multiple of significance.
- Example Ceiling(41.88, 10) will give 50 and Ceiling of 41.88 to 5 will give 45.
- Below is the C# function which gives the same result as Ceiling in MS Excel.



       public int Ceiling(double input, int ceilTo)
        {
            if ((input % ceilTo) != 0)
            {
                return ((int)(input / ceilTo) * ceilTo) + ceilTo;
            }
            else
            {
                return Convert.ToInt32(input);
            }
        }

MS Excel like Round function in c#.

2010-02-26T05:28:00.002-05:00

1. Excel Round function behaves differently when we compare with C# Math.Round() method.
2. Also Excel Round allows Round to -1, -2... example Round(121,-1) = 120. This is not allowed in Math.Round()
3. Say if we want to Round 1234.5678 to nearest integer value then Math.Round() returns 1234 where as MS Excel Round gives 12345.
4. Below is a C# function that gives similar result as MS Excel Round and also allows negative rounding.


   public double roundNum(double num, int place)
   { 
     double n; 
     n = num * Math.Pow(10, place); 
     n = Math.Sign(n) * Math.Abs(Math.Floor(n + .5)); 
     return n / Math.Pow(10, place); 
   }

Note: Visual Studio 2005 allows us to mention Round Up or Round down for Math.Round() method.

Solution: How to change css class for an element in jquery?

2009-11-03T10:23:00.001-05:00

In order to change the CSS class applied to an element using jQuery we can use methods like
addClass() and .removeClass()


$("#divId").addClass("classname");

$("#divId").removeClass("classname");

But if we want to change or toggle CSS class between two classes during some events like button click we can use method toggleClass() like below.

Say on click we need to change class from "btn_submit" and "btn_submit_active" or vise versa
if element has class "btn_submit_active" toggle to use "btn_submit". here we use toggleClass() method twise.


  $("#divId").toggleClass("btn_submit");
  $("#divId").toggleClass("btn_submit_active");

Visual Studio 2010 and .NET 4.0 Beta 2 Released

2009-10-21T16:12:00.001-04:00

Visual Studio 2010 and .Net Framework 4.0 Beta 2 is released this wednesday.
This is available for download in MSDN here http://go.microsoft.com/fwlink/?LinkID=151797

Have a look at the style and view in the below image.

VS 2010 Features or Key Areas of improvements

- Advances for ASP.NET web development
- WPF and WinForms client development
- SharePoint development
- Silverlight development
- Data development
- Parallel computing development and
- cloud computing development.
- Lot of improvements in IDE and other tools
- Improvements in programming languages like C#

- Easy to install and use TFS for version management

We can have VS 2010 along with VS 2008 in our system.

JSON Serialization in VS 2008

2009-10-20T14:53:00.003-04:00

Say we need to convert serialize C# object to JSON string and transfer that to client side to be used in Javascript. DataContract attribute is added to a class and DataMember attribute is added for all members that need be serialized.


[DataContract]
 public class Employee
    {
        #region "Private Variables"
        private string name = string.Empty;
        private string id = string.Empty;
        #endregion

        #region "Public Properties"
        [DataMember]
        public string Name
        {
            get
            {
                return this.name;
            }
            set
            {
                this.name = value;
            }
        }
        [DataMember]
        public string ID
        {
            get
            {
                return this.id;
            }

            set
            {
                this.id = value;
            }
        }
   }

Now in order to convert the above mentioned class object to JSON string use below code.


Employee obj = new Employee();
DataContractJsonSerializer serializer = new DataContractJsonSerializer(obj.GetType());
using (MemoryStream ms = new MemoryStream())
 {
       serializer.WriteObject(ms, obj);
       ms.Flush();
       byte[] bytes = ms.GetBuffer();
      string jsonString = Encoding.UTF8.GetString(bytes, 0, bytes.Length).Trim('\0');
      return jsonString;
 }

Junior Software Developer

2009-10-04T04:55:00.001-04:00

Job Description

Position: Junior Software Developer
Apply Now
Requirements:

• Knowledge and experience in C# ,ASP.NET SQL and XML (academic project in NET is Must)
• Experience working in a variety of team sizes and excellent communication and interpersonal skills.

Desired Candidate Profile
We are looking to add a Junior Developer to our Engineering Team to assist in application development and daily operations. With a variety of coding languages and platforms, it is a challenging position that requires a desire to learn.

For More Details Click Here

Validating textbox to not allow invalid characters in all cases.

2009-09-18T13:43:00.003-04:00

In order to allow user to enter only certain characters in a textbox and also to control the maximum length of multiline textbox use the below function by calling it on onkeypress for a textbox.

And also to handle the cases where the user copy paste the content containing the invalid characters first we will prepare the regular expression to and check for invalid characters and replace with empty (remove invalid characters from pasted content).

Then we will get the pressed key and check the key pressed by user while entering the text into a textbox and check if it is in part of valid character and based on which we will stop user from entering invalid characters.

One important thing here is we need to allow few keys like backspace, Arrow keys, Home, End etc.. for that we will make sure that the key pressed is not in (27, 9, 32, 8, 36, 37, 35, 13, 0).


function ValidateName(name,e)
{
        var nameRegex = /^[A-Za-z',.-]{0,50}$/;
        while (!name.value.match(nameRegex)) 
        {
            name.value = name.value.replace(/[^a-zA-Z,'.-]+/, "");
        }
        e = e || window.event;
        var allow = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.,'-";
        var allowKeys = new Array(27, 9, 32, 8, 36, 37, 35, 13, 0);
        var keycode = e.which || e.keyCode;
        if (allow.indexOf(String.fromCharCode(keycode)) < 0)
        {
             for (var i = 0; i < allowKeys.length; i++)
             {
                 if (allowKeys[i] == keycode)
                 {
                       return true;
                  }
              }
              return false;
          }
       return true;
    }

Call this function in onkeypress event as shown below.


Onkeypress = "return ValidateName(this,event)"

To get the count of messages in a MSMQ Queue in C#.NET

2009-08-17T11:39:00.000-04:00

There is no direct property provided with MessageQueue class.
We can use GetMessageEnumerator2 to get the enumerator to enumerate and get the count of number of messages present in the queue.

The below code is used for getting the messages count from a transactional queues


public static int GetMessageCount(MessageQueue messageQueue)
{
   int count = 0;
   using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required))
   {
      MessageEnumerator enumerator = messageQueue.GetMessageEnumerator2();
      while (enumerator.MoveNext(new TimeSpan(0, 0, 0)))
      {
         count++;
      }
   }

   return count;
}

The below code is used for getting the messages count from a non transactional queues


public static int GetMessageCount(MessageQueue messageQueue)
{
   int count = 0;
   using (TransactionScope scope = new TransactionScope(TransactionScopeOption.Required))
   {
      MessageEnumerator enumerator = messageQueue.GetMessageEnumerator2();
      while (enumerator.MoveNext(new TimeSpan(0, 0, 0)))
      {
         count++;
      }
   }

   return count;
}

Silverlight 3 Released

2009-07-29T13:56:00.000-04:00

Silverlight 3 and associated developer tools have been released! Visit the Silverlight Community site to download all you need to build great Web experiences with Silverlight 3. You can also learn more by watching the new videos, reviewing the Quickstarts or reading about some success stories and what is new in Silverlight 3.

Fix: Cutom Javascript Does not load in case of Partial Postback using UpdatePanel.

2009-07-17T11:33:00.000-04:00

When we are using Update Panel for asynchronous Partial page postback static javasctipt files will not be loaded and we may see error like "Permission Denied" or something like

Error: Sys.ScriptLoadFailedException: The script 'http://localhost/Js/FreeTextBox/FTB-ToolbarItems.js' failed to load. Check for:
Inaccessible path.
Script errors. (IE) Enable 'Display a notification about every script error' under advanced settings.
Missing call to Sys.Application.notifyScriptLoaded().

This scenario occurs like when we are using a cutom Text Editor inside a UpdatePanel which uses Javascript and loads javascript files.

In order to fix this issue.
We need to call Sys.Application.notifyScriptLoaded() once the file is loaded for that
Just we need to add below code at the last line of all such javascript files


if (typeof(Sys) != "undefined") { if (typeof(Sys.Application) != "undefined") { Sys.Application.notifyScriptLoaded(); }}

Happy Coding....

Alternative: $(document).ready handler will not be fired on asynchronous postback.

2009-07-03T04:26:00.000-04:00

Like in case we are using updatepanel under which we have postback button along with jQuery calender textbox.

And datepicker is attached to a textbox in document ready event handler.

Upon postback jquery calender will not work as $(document).ready will not be called on
asynchronous postback
so to make sure this to work we have to call a Javascript function after an UpdatePanel asynchronous postback using the following line


 Sys.WebForms.PageRequestManager.getInstance().add_endRequest(showdatepicker);

here showdatepicker is a function which will attach jQuery datepicker to a textbox.

Fundamentals of jQuery

2009-06-07T12:21:00.015-04:00

Introduction:
. jQuery is a fast, lightweight JavaScript library that is CSS3 compliant and supports many browsers.
. The jQuery framework is extensible and very nicely handles DOM manipulations, CSS, AJAX, Events and Animations.
Selector: An expression for identifying target elements on a page that allows us to easily identify and grab the elements we need.
. jQuery focuses on retrieving elements from our HTML pages and performing operations upon them.


<button
type="button"
onclick="document.getElementById('xyz').style.color='red';">
Click Me
</button>

window.onload = function() {
document.getElementById('testButton').onclick = makeItRed;
};

. Consistent across all browsers.
. Solves major javascript problems
. Easily extendable

jQuery wrapper
. To collect a group of elements, we use the simple syntax $(selector) or jQuery(selector)
. The $() function (an alias for the jQuery() function) returns a special Java-Script object containing an array of the DOM elements that match the selector.
. This object possesses a large number of useful predefined methods that can acton the group of elements.
. This type of construct is termed a wrapper because it wraps the matching element(s) with extended functionality.$("div.notLongForThisWorld").fadeOut();
. A special feature of a large number of these methods, which we often refer to as jQuery commands, is that when they’re done with their action (like a fading-out operation), they return the same group of elements, ready for another action.$("div.notLongForThisWorld").fadeOut().addClass("removed");

. Along with selectors that we already know jQuery supports all selectors in CSS and also custom selectors
Here are a few examples.

$("p:even"); - This selector selects all even <p> elements.
$("tr:nth-child(1)"); - This selector selects the first row of each table.
$("body > div"); - This selector selects direct <div> children of <body>.
$("a[href$=pdf]"); - This selector selects links to PDF files.
$("body > div:has(a)") - This selector selects direct <div> children of <body>-containing links. http://docs.jquery.com/Selectors

Utility functions

. jQuery’s $() function – along with wrapping elements to be operated upon it serves as a namespace prefix for a handful of general purpose Utility functions.
. Notation: $.trim(someString); / jQuery.trim(someString);

The document ready handler
. Unobtrusive JavaScript - behavior is separated from structure
We willll be performing operations on the page elements outside of the document markup that creates them. In order to achieve this, we need a way to wait until the DOM elements of the page are fully loaded before those operations execute.
. In the zebra-striping example, the entire table must load before striping can be applied.
window.onload = function() {
$("table tr:nth-child(even)").addClass("even");
};
. The onload handler for the window instance is used for this purpose, executing statements after the entire page is fully loaded.
. Browser will delay calling onload till DOM tree is created and all images/other external
resources are fully loaded.
. Better approach would be to wait till DOM tree is ready and before executing scripts to apply rich behavior. jQuery provides a simple means to trigger the execution of code once the DOM tree, but not external image resources, has loaded.
$(document).ready(function() {
$("table tr:nth-child(even)").addClass("even");
});
. We can use this technique multiple times within the same HTML document

Extending jQuery

. jQuery is designed to be easily extended with additional functionality.
. jQuery makes it easy to extend its set of functions by extending the wrapper returned when we call $().


$.fn.disable = function()
{
return this.each
(
function()
{
if (typeof this.disabled != "undefined") this.disabled = true;
}
);
}

. Our brand new disable() method will support chaining like many of the native jQuery methods. We’ll be able to write
$("form#myForm input.special").disable().addClass("moreSpecial");

. Moreover, enterprising jQuery users have extended jQuery with sets of useful
functions that are known as plugins.

Selecting and Manipulating elements

Selectors Lab: http://www.aacr9.com/jquery/jQueryInAction/jqia.source/chapter2/lab.selectors.htmlhttp://www.codylindley.com/jqueryselectors/
. Using the basic CSS selectors like
■ a—This selector matches all link (<a>) elements.
■ #specialID—This selector matches elements that have an id of specialID.
■ .specialClass—This selector matches elements that have the class of specialClass.
■ a#specialID.specialClass—This selector matches links with an id of specialID and a class of specialClass.
■ p a.specialClass—This selector matches links with a class of specialClass declared within <p> elements.

. To select elements using jQuery, we wrap the selector in $() Ex: $("p a.specialClass")
. With a few exceptions , jQuery is fully CSS3 compliant.
. jQuery doesn’t depend upon the CSS implementation of the browser it’s running within. Even if the browser doesn’t implement a standard CSS selector correctly, jQuery will correctly select elements according to the rules of the World Wide Web Consortium (W3C) standard.
. Using child, container, and attribute selectors

. Only a single level of nesting is supported. Although it’s possible to nest one level , such as foo:not(bar:has(baz)) , li:not(:has(a)) additional levels of nesting, such as foo:not(bar:has(baz:eq(2))) aren’t supported.
Selecting by position:
. Sometimes, we’ll need to select elements by their position on the page or in relation to other elements. We might want to select the first link on the page, or every other paragraph, or the last list item of each list.
. For more advanced selectors, jQuery uses the next generation of CSS supported by Mozilla Firefox, Internet Explorer 7, Safari, and other modern browsers.
. These advanced selectors include selecting the direct children of some elements, elements that occur after other elements in the DOM, and elements with attributes matching certain conditions.

. Only a single level of nesting is supported. Although it’s possible to nest one level , such as foo:not(bar:has(baz)) , li:not(:has(a)) additional levels of nesting, such as foo:not(bar:has(baz:eq(2))) aren’t supported.
Selecting by position:
. Sometimes, we’ll need to select elements by their position on the page or in relation to other elements. We might want to select the first link on the page, or every other paragraph, or the last list item of each list.

. The nth-child selector starts counting from 1, whereas the other selectors start counting from 0.
. :eq (absolute position selector) is 0-based, but :nth-child is 1-based.

. Ex: To select only enabled checked checkboxes :checkbox:checked:enabled

. Using the :not filter – To inverse all these filters To select non-check box <input> elements, we use
input:not(:checkbox)
. We can apply the :not filter to filter selectors, but not to find selectors. The
Selector div p:not(:hidden) is a perfectly valid selector, but div :not(p:hidden) isn’t.
. Along with all these selectors we have a plugin “Basic Xpath”. This plugin adds in basic XPath selector functionality
. Plug-in supports /, //, *,[@p=value],[@p], position()
$("<div>Hello</div>")
. This expression creates a new <div> element ready to be added to the page
. We can run any jQuery commands that we could run on wrapped element sets of existing elements on the newly created fragment.
. $("<div class=‘test'>I have foo!</div><div>I don't</div>").filter(".test").click(function() {
alert("I'm foo!");}).end().appendTo("#someParentDiv");
. We can get a lot accomplished without writing a lot of script.

. Determining the size of the wrapped set $('a').size()
. Obtaining elements from the wrapped set jQuery allows us to treat the wrapped set as a JavaScript array, we can use simple array indexing to obtain any element in the wrapped list by position. $('img[alt]')[0] or $('img[alt]').get(0) Ex: var allLabeledButtons = $('label+button').get();
. Adding more elements to the wrapped setLet’s say that we want to match all elements that have either an alt or a title attribute.$('img[alt],img[title]') or $('img[alt]').add('img[title]')$('img[alt]').add(someElement)$('p').add('<div>Hi there!</div>')
. $('img[alt]').addClass('thickBorder').add('img[title]‘).addClass('seeThrough')
not() method to remove elements from the wrapped set anywhere within a jQuery chain of commands - $('img[title]').not('[title*=puppy]')
the selectors we can pass to the not() method are limited to filter
. Expressions that omit any element reference (allowing it to imply all element types).

. In case we want to filter the wrapped set in ways that are difficult or impossible to express with a selector expression. Instead of iterating through all the elements we can use jQuery’s filter()
. The filter() method, when passed a function, invokes that function for each wrapped element and removes any element whose function invocation returns the value false.
. Each invocation has access to the current wrapped element via the function context (this) in the body of the filtering function. Any element that returns an invocation of false is removed from the set.
Ex : $('td').filter(function(){return this.innerHTML.match(/^\d+$/)})
. The filter() method can also be used with a passed selector expression that conforms to the same constraints that we described earlier for the not() method, namely, filter selectors with an implied element type.
$('img').addClass('seeThrough').filter('[title*=dog]‘).addClass('thickBorder')
. Subsets of the wrapped set To obtain a subset of the wrapped set, based on the position of elements within the set.
. slice(begin,end)
. To grab elements from the end of the wrapped set, the statement - $('*').slice(4);
. Getting wrapped sets using relationships These methods give us a large degree of freedom to select elements from the DOM, based on relationships to the other DOM elements.

. The find() method lets us search through an existing wrapped set and returns a new set that contains all elements that match a passed selector expression. - wrappedSet.find('p cite')
. jQuery also provides a method to find elements that contain a specified string. - $('p').contains('Lorem ipsum')
. The is() method returns true if at least one element matches the selector, and false if not . - is(selector)
. The easiest way to inspect or modify the component elements of a matched set is with the each() command.
Ex: $('img').each(function(n)
{
this.alt='This is image['+n+'] with an id of '+this.id;
});
. To collect all values for a specific property into an array using each(), as follows:
var allAlts = new Array();
$('img').each(function(){
allAlts.push(this.alt);
});
. var altValue = $('#myImage')[0].alt;
. attr(name) - To obtain the values assigned to the specified attribute for the first element in the matched set. - $("#myImage").attr("custom")
. Setting attribute values: attr(name,value)
. Setting multiple attributes at a time: attr(attributes) Ex: $('input').attr({ value: '', title: 'Please enter a value' });
. Removing Attributes: removeAttr(name)
. jQuery attr() normalized-access names

.Changing Element Styling:
addClass(names)
removeClass(names)
toggleClass(name)
css(name,value) – Applying Styles directly onto the elements
css(properties)
css(name)

Rounding a number after decimal point using Vb script Format functions

2009-05-24T09:49:00.003-04:00

Below is the function in the vbscript which will round the number up to two digits after decimal number.



<Script language="VBScript">

Function Roundnumber(Decnumber,numlength)
    
    Roundnumber = FormatCurrency(Decnumber,numlength,,,0)     

    Roundnumber = FormatNumber(Decnumber,numlength,,,0)   

End Function

</Script>

<Script language="JavaScript">

function roundnumjavascript(number,length)

{

       document.getElementById('textBox1').value= Roundnumber(number,length)

}

</Script>

In HTML

<input type="text" id="textBox1"/>

<input type="button" id="btnround" value="Roundnum" onclick="roundnumjavascript(document.getElementById('textBox1').value,2);"/>

Calling VB Script Function from inside a Javascript function.

2009-05-24T09:28:00.003-04:00

Calling VB script function in javascript is as simple as calling another javascript function.

Let us see with a simple example.
First we will create a function in VB Script to add two numbers.

Call this VB Script function from javascript

Following is html page to input values to add and shows the result in other


<html>

<head>

<script language="VbScript">

      

      Function Add(a,b)

            Add=CInt(a)+CInt(b)

      End Function

 

</script>

 

<script language="JavaScript">

      

      function callingVbfun()

     {

          document.getElementById('txtResult').value= Add(document.getElementById('txtNumber1').value,document.getElementById('txtNumber2').value)

     }

 

</script>

</head>

<body></body>

<form>

    <input type-"text" id="txtNumber1"/>

    <input type-"text" id="txtNumber2"/>

    <input type-"text" id="txtResult"/>

     <input type-"button" id="btn" value="Add" onclick="callingVbfun()"/>

</form>

</html>

How to call multiple Javascript methods on window load using onload handler

2009-05-14T10:01:00.002-04:00

We know that when we cannot assign mutilple functions to onload handler in javascript. It will just ovveride the previous function.

In order to set mutliple functions we need to consider Array and add all methods to that array.(functions can be added in Page or Usercontrol).

First Create onloadManager array.


if (!window.onloadManager)
{
window.onloadManager = new Array();

//add existing method to array

if (window.onload) {window.onloadManager[0] = window.onload;}

//Loop through array and execute each on onload
window.onload = function() { 
for (index in window.onloadManager) { window.onloadManager[index](); }
};
}

Adding functions to onloadmanager array.


window.onloadManager[window.onloadManager.length] = function()
{

alert('function1 added');

};

Say in other user control on same page we add one more function.


window.onloadManager[window.onloadManager.length] = function()
{

alert('function2 added');

};