Class And Objects

Introduction:

In our world we have classes and objects for those classes. Everything in our world is considered to be an object. For example, people are objects, animals are objects too, minerals are objects; everything in the world is an object. Easy, right? But what about classes?

In our world we have to differentiate between objects that we are living with. So we must understand that there are classifications (this is how they get the name and the concepts of the Class) for all of those objects. For example, I'm an object, David is object too, Maria is another object. So we are from a people class (or type). I have a dog called Ricky so it's an object. My friend's dog, Doby, is also an object so they are from a Dogs class (or type).

A C# Class is considered to be the primary building block of the language.

We use classes as a template to put the properties and functionalities or behaviors in one building block for a group of objects and after that we use the template to create the objects we need.

The class: A building block that contains the properties and functionalities that describe some group of objects. We can create a class Person that contains:

1. The properties of any normal person on the earth like: hair color, age, height, weight, eye color.
2. The functionalities or behaviors of any normal person on the earth like: drink water, eat, go to the work.

There are 2 kinds of classes: The built-it classes that come with the .NET Framework, called Framework Class Library, and the programmer defined-classes which we create ourselves.

The class contains data (in the form of variables and properties) and behaviors (in the form of methods to process these data).

The object: It's an object of some classification (or class, or type) and when you create the object you can specify the properties of that object. What I mean here is: I, as an object, can have different properties (hair color, age, height, weight) than you as another object. For example, I have brown eyes and you have green eyes. When I create 2 objects I will specify a brown color for my object's eye color property and I will specify a green color for your object's eye color property.



class Person
{
public int Age;
public string HairColor;
}

This is our simple class which contains 2 variables.

static void Main(string[] args)
{
Person Michael = new Person();
Person Mary = new Person();

// Specify some values for the instance variables
Michael.Age = 20;
Michael.HairColor = "Brown";
Mary.Age = 25;
Mary.HairColor = "Black";
// print the console's screen some of the variable's values
Console.WriteLine("Michael's age = {0}, and Mary's age = {1}",Michael.Age,
Mary.Age);
Console.ReadLine();
}


So we begin our Main method by creating 2 objects of type Person. After creating the 2 objects we initialize the instance variables for object Michael and then for object Mary. Finally we print some values to the console. Here, when you create the Michael object, the C# compiler allocates a memory location for the 2 instance variables to put the values there. Also, the same thing with the Mary object; the compiler will create 2 variables in memory for Mary object. So each object now contains different data.


Using Properties in Functions:

class Person
{
private int age;
private string hairColor;
public int Age
{
get
{
return age;
}
set
{
if(value <= 65 && value >= 18)
{
age = value;
}
else
age = 18;
}
}
public string HairColor
{
get
{
return hairColor;
}
set
{
hairColor = value;
}
}
}

I made some modifications, but focus on the new 2 properties that I created. So the property consists of 2 accessors. The get accessor, responsible of retrieving the variable value, and the set accessor, responsible of modifying the variable's value. So the get accessor code is very simple. We just use the keyword return with the variable name to return its value. So the following code:

get
{
return hairColor;
}

returns the value stored in hairColor.


static void Main(string[] args)
{
Person Michael = new Person();
Person Mary = new Person();

// Specify some values for the instance variables
Michael.Age = 20;
Michael.HairColor = "Brown";
Mary.Age = 25;
Mary.HairColor = "Black";

// print the console's screen some of the variable's values
Console.WriteLine("Michael's age = {0}, and Mary's age = {1}",Michael.Age,
Mary.Age);
Console.ReadLine();
}

Here I created the same objects from the last example, except that I used only properties to access the variable instead of accessing it directly. Look at the following line of code

Michael.Age = 20;

When you assign a value to the property like that C# will use the set accessor. The great thing with the set accessor is that we can control the assigned value and test it; and maybe change to in some cases. When you assign a value to a property C# changes the value in a variable and you can access the variable's value using the reserved keyword value exactly as I did in the example. Let's see it again here.

set
{
if(value <= 65 && value >= 18)
{
age = value;
}
else
age = 18;
}

Here in the code I used if statement to test the assigned value because for some reason I want any object of type Person to be aged between 18 and 65. Here I test the value and if it is in the range then I will simply store it in the variable age. If it's not in the range I will put 18 as a value to age.

We create a class by defining it using the keyword class followed by the class name:

class Person

Then we open a left brace "{" and write our methods and properties. We then close it with a right brace "}". That's how we create a class. Let's see how we create an instance of that class.

In the same way as we declare a variable of type int we create an object variable of Person type with some modifications:

int age;
Person Michael = new Person();

In the first line of code we specified integer variable called age. In the second line we first specified the type of Object we need to create, followed by the object's name, followed by a reserved operator called new. We end by typing the class name again followed by parentheses "()".

Let's understand it step-by-step. Specifying the class name at the beginning tells the C# Compiler to allocate a memory location for that type (the C# compiler knows all the variables and properties and methods of the class so it will allocate the right amount of memory). Then we followed the class name by our object variable name that we want it to go by. The rest of the code "= new Person();" calls the object's constructor. We will talk about constructors later but for now understand that the constructor is a way to initialize your object's variable while you are. For example, the Michael object we created in the last section can be written as following :

Person Michael = new Person(20, "Brown");

Here I specified the variable's values in the parameter list so I initialized the variables while creating the object.


Source: DevArticles

validation in ASP.Net

TITLE	EXPRESSION	DESCRIPTION	MATCHES
NUMBERS	^[0-9]*$	only numbers are allowed	12345 | 12345678
CURRENCY	^\d+(?:\.\d{0,2})?$	Useful for checking currency amounts, such 5 or 5.00 or 5.25	1 | 1.23 | 1234.45
alpha numeric	^[a-zA-Z0-9]+$	it will check for alphanumeric (Alpha Numeric) values.	adad1213 | 1231dfadfa | dfad123dfasdfs

ASCII Character Set

Character	Entity Number	Entity Name	Description
"	"	"	quotation mark
'	'	' (does not work in IE)	apostrophe
&	&	&	ampersand
<	&#60;	&lt;	less-than
>	&#62;	&gt;	greater-than

ISO 8859-1 Symbols:

Character	Entity Number	Entity Name	Description
	 	 	non-breaking space
¡	¡	¡	inverted exclamation mark
¢	¢	¢	cent
£	£	£	pound
¤	¤	¤	currency
¥	¥	¥	yen
¦	¦	¦	broken vertical bar
§	§	§	section
¨	¨	¨	spacing diaeresis
©	©	©	copyright
ª	ª	ª	feminine ordinal indicator
«	«	«	angle quotation mark (left)
¬	¬	¬	negation
­	­	­	soft hyphen
®	®	®	registered trademark
¯	¯	¯	spacing macron
°	°	°	degree
±	±	±	plus-or-minus
²	²	²	superscript 2
³	³	³	superscript 3
´	´	´	spacing acute
µ	µ	µ	micro
¶	¶	¶	paragraph
·	·	·	middle dot
¸	¸	¸	spacing cedilla
¹	¹	¹	superscript 1
º	º	º	masculine ordinal indicator
»	»	»	angle quotation mark (right)
¼	¼	¼	fraction 1/4
½	½	½	fraction 1/2
¾	¾	¾	fraction 3/4
¿	¿	¿	inverted question mark
×	×	×	multiplication
÷	÷	÷	division

ISO 8859-1 Characters:

Character	Entity Number	Entity Name	Description
À	À	À	capital a, grave accent
Á	Á	Á	capital a, acute accent
Â	Â	Â	capital a, circumflex accent
Ã	Ã	Ã	capital a, tilde
Ä	Ä	Ä	capital a, umlaut mark
Å	Å	Å	capital a, ring
Æ	Æ	Æ	capital ae
Ç	Ç	Ç	capital c, cedilla
È	È	È	capital e, grave accent
É	É	É	capital e, acute accent
Ê	Ê	Ê	capital e, circumflex accent
Ë	Ë	Ë	capital e, umlaut mark
Ì	Ì	Ì	capital i, grave accent
Í	Í	Í	capital i, acute accent
Î	Î	Î	capital i, circumflex accent
Ï	Ï	Ï	capital i, umlaut mark
Ð	Ð	Ð	capital eth, Icelandic
Ñ	Ñ	Ñ	capital n, tilde
Ò	Ò	Ò	capital o, grave accent
Ó	Ó	Ó	capital o, acute accent
Ô	Ô	Ô	capital o, circumflex accent
Õ	Õ	Õ	capital o, tilde
Ö	Ö	Ö	capital o, umlaut mark
Ø	Ø	Ø	capital o, slash
Ù	Ù	Ù	capital u, grave accent
Ú	Ú	Ú	capital u, acute accent
Û	Û	Û	capital u, circumflex accent
Ü	Ü	Ü	capital u, umlaut mark
Ý	Ý	Ý	capital y, acute accent
Þ	Þ	Þ	capital THORN, Icelandic
ß	ß	ß	small sharp s, German
à	à	à	small a, grave accent
á	á	á	small a, acute accent
â	â	â	small a, circumflex accent
ã	ã	ã	small a, tilde
ä	ä	ä	small a, umlaut mark
å	å	å	small a, ring
æ	æ	æ	small ae
ç	ç	ç	small c, cedilla
è	è	è	small e, grave accent
é	é	é	small e, acute accent
ê	ê	ê	small e, circumflex accent
ë	ë	ë	small e, umlaut mark
ì	ì	ì	small i, grave accent
í	í	í	small i, acute accent
î	î	î	small i, circumflex accent
ï	ï	ï	small i, umlaut mark
ð	ð	ð	small eth, Icelandic
ñ	ñ	ñ	small n, tilde
ò	ò	ò	small o, grave accent
ó	ó	ó	small o, acute accent
ô	ô	ô	small o, circumflex accent
õ	õ	õ	small o, tilde
ö	ö	ö	small o, umlaut mark
ø	ø	ø	small o, slash
ù	ù	ù	small u, grave accent
ú	ú	ú	small u, acute accent
û	û	û	small u, circumflex accent
ü	ü	ü	small u, umlaut mark
ý	ý	ý	small y, acute accent
þ	þ	þ	small thorn, Icelandic
ÿ	ÿ	ÿ	small y, umlaut mark

All Country List in a Dropdownlist c#

using System.Collections.Generic;
using System.Globalization;



Page_Load

{
PopulateCountryName(ddl_country);
}



private void PopulateCountryName(DropDownList dropDown)
{
Hashtable h = new Hashtable();

Dictionary<string, string > objDic = new Dictionary<string, string >();

foreach (CultureInfo ObjCultureInfo in CultureInfo.GetCultures(CultureTypes.SpecificCultures))
{

RegionInfo objRegionInfo = new RegionInfo(ObjCultureInfo.Name);

if (!objDic.ContainsKey(objRegionInfo.EnglishName))
{
objDic.Add(objRegionInfo.EnglishName, objRegionInfo.TwoLetterISORegionName.ToLower());
}
}
List<KeyValuePair<string, string>> myList = new List<KeyValuePair<string, string>>(objDic);
myList.Sort(

delegate(KeyValuePair<string, string> firstPair,

KeyValuePair<string, string> nextPair)
{
return firstPair.Value.CompareTo(nextPair.Value);
}
);
foreach (KeyValuePair<string, string> val in myList)
{
dropDown.Items.Add(new ListItem(val.Key, val.Value));
}
}


Working with Accordion Pane

Working with Accordion Pane

In Registry:


<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>





<cc1:Accordion ID="Accordion1" runat="server" SelectedIndex="0" Width="100%"
HeaderCssClass="accordionHeader" HeaderSelectedCssClass="accordionHeaderSelected"
ContentCssClass="accordionContent" FadeTransitions="false" FramesPerSecond="40"
TransitionDuration="250" AutoSize="None" RequireOpenedPane="false"
SuppressHeaderPostbacks="true">
<Panes>




<cc1:AccordionPane ID="AC" runat="server">
<Header>
<asp:Label ID = "lbl_PersonelDetails" Text = "Course Details" Font-Bold="True"
Font-Names="Verdana" Font-Size="Small" runat = "server"></asp:Label>
</Header>
<Content>

<table class="TAB_INNER">
<tbody><tr> <td>
Content I
</td>
</tr>
</tbody></table>
</Content>
</cc1:AccordionPane>

<cc1:AccordionPane ID="AD" runat="server" Width="100%">
<Header>
<asp:Label ID = "Label2" Text = "Department Details" Font-Bold="True"
Font-Names="Verdana" Font-Size="Small" runat = "server"></asp:Label>
</Header>
<Content>
<table class="TAB_INNER">
<tbody><tr> <td>
Content I
</td>
</tr>
</tbody></table>

</Content>
</cc1:AccordionPane>

</Panes>

</cc1:Accordion>





MDI Parent WinForms c#

Close All Mdi Child forms in Mdi Parent C#

foreach (System.Windows.Forms.Form form1 in this.MdiChildren)
{
form1.Close();
}

SQL Server Questions only

Revisiting basic syntax of SQL?
What are “GRANT” and “REVOKE’ statements?
What is Cascade and Restrict in DROP table SQL?
What is a DDL, DML and DCL concept in RDBMS world?
What are different types of joins in SQL?
What is “CROSS JOIN”?
You want to select the first record in a given set of rows?
How do you sort in SQL?
How do you select unique rows using SQL?
Can you name some aggregate function is SQL Server?
What is the default “SORT” order for a SQL?
What is a self-join?
What's the difference between DELETE and TRUNCATE ?
Select addresses which are between ‘1/1/2004’ and ‘1/4/2004’?
What are Wildcard operators in SQL Server?
What’s the difference between “UNION” and “UNION ALL” ?
What are cursors and what are the situations you will use them?
What are the steps to create a cursor?
What are the different Cursor Types?
What are “Global” and “Local” cursors?
What is “Group by” clause?
What is ROLLUP?
What is CUBE?
What is the difference between “HAVING” and “WHERE” clause?
What is “COMPUTE” clause in SQL?
What is “WITH TIES” clause in SQL?
What does “SET ROWCOUNT” syntax achieves?
What is a Sub-Query?
What is “Correlated Subqueries”?
What is “ALL” and “ANY” operator?
What is a “CASE” statement in SQL?
What does COLLATE Keyword in SQL signify?

Convert a file into bytes C#

private void GetOpenFileDialog()
{
openFileDialogX.CheckPathExists = true;
openFileDialogX.Filter = "Text files (*.text)|*.txt|doc files (*.doc)|*.doc|pdf files (*.pdf)|*.pdf|excel files(*.xls)|*.xls|excel files07(*.xlsx)|*.xlsx";
openFileDialogX.Multiselect = false;
openFileDialogX.AddExtension = true;
openFileDialogX.ValidateNames = true;
openFileDialogX.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
openFileDialogX.ShowDialog();


Fname = openFileDialogX.FileName.ToString();
Fsize = openFileDialogX.FileName.Length;
Fext = System.IO.Path.GetExtension(Fname);



FileInfo fi= new FileInfo(Fname);
long numbyt= fi.Length;

FileStream FS = new FileStream(Fname, FileMode.Open, FileAccess.Read);
BinaryReader BR = new BinaryReader(FS);
filbyt = BR.ReadBytes(Convert.ToInt32(numbyt));




}




source: http://www.dotnetspider.com/projects/512-Store-Retrieve-pdf-txt-doc-Images-Sql-server-database.aspx

Question Bunch C#

Question Bunch V

Q81. What technique is used to figure out that the page request is a postback?

Ans. The IsPostBack property of the page object may be used to check whether the page request is a postback or not. IsPostBack property is of the type Boolean.



Q82. Which event of the ASP.NET page life cycle completely loads all the controls on the web page?

Ans. The Page_load event of the ASP.NET page life cycle assures that all controls are completely loaded. Even though the controls are also accessible in Page_Init event but here, the viewstate is incomplete.



Q83. How is ViewState information persisted across postbacks in an ASP.NET webpage?

Ans. Using HTML Hidden Fields, ASP.NET creates a hidden field with an ID="__VIEWSTATE" and the value of the page's viewstate is encoded (hashed) for security.



Q84. What is the ValidationSummary control in ASP.NET used for?

Ans. The ValidationSummary control in ASP.NET displays summary of all the current validation errors.



Q85. What is AutoPostBack feature in ASP.NET?

Ans. In case it is required for a server side control to postback when any of its event is triggered, then the AutoPostBack property of this control is set to true.



Q86. What is the difference between Web.config and Machine.Config in .NET?

Ans. Web.config file is used to make the settings to a web application, whereas Machine.config file is used to make settings to all ASP.NET applications on a server(the server machine).



Q87. What is the difference between a session object and an application object?

Ans. A session object can persist information between HTTP requests for a particular user, whereas an application object can be used globally for all the users.



Q88. Which control has a faster performance, Repeater or Datalist?

Ans. Repeater.



Q89. Which control has a faster performance, Datagrid or Datalist?

Ans. Datalist.



Q90. How to we add customized columns in a Gridview in ASP.NET?

Ans. Make use of the TemplateField column.



Q91. Is it possible to stop the clientside validation of an entire page?

Ans. Set Page.Validate = false;



Q92. Is it possible to disable client side script in validators?

Ans. Yes. simply EnableClientScript = false.



Q93. How do we enable tracing in .NET applications?

Ans. <%@ Page Trace="true" %>



Q94. How to kill a user session in ASP.NET?

Ans. Use the Session.abandon() method.



Q95. Is it possible to perform forms authentication with cookies disabled on a browser?

Ans. Yes, it is possible.



Q96. What are the steps to use a checkbox in a gridview?

Ans.



OnCheckedChanged="Check_Clicked">





Q97. What are design patterns in .NET?

Ans. A Design pattern is a repeatitive solution to a repeatitive problem in the design of a software architecture.



Q98. What is difference between dataset and datareader in ADO.NET?

Ans. A DataReader provides a forward-only and read-only access to data, while the DataSet object can carry more than one table and at the same time hold the relationships between the tables. Also note that a DataReader is used in a connected architecture whereas a Dataset is used in a disconnected architecture.



Q99. Can connection strings be stored in web.config?

Ans. Yes, in fact this is the best place to store the connection string information.



Q100. Whats the difference between web.config and app.config?

Ans. Web.config is used for web based asp.net applications whereas app.config is used for windows based applications.

Question Bunch IV

Q61. Is a delegate a type-safe functions pointer?
Ans. Yes

Q62. What is the return type of an event in .NET?
Ans. There is No return type of an event in .NET.

Q63. Is it possible to specify an access specifier to an event in .NET?
Ans. Yes, though they are public by default.

Q64. Is it possible to create a shared event in .NET?
Ans. Yes, but shared events may only be raised by shared methods.

Q65. How to prevent overriding of a class in .NET?
Ans. Use the keyword NotOverridable in VB.NET and sealed in C#.

Q66. How to prevent inheritance of a class in .NET?
Ans. Use the keyword NotInheritable in VB.NET and sealed in C#.

Q67. What is the purpose of the MustInherit keyword in VB.NET?
Ans. MustInherit keyword in VB.NET is used to create an abstract class.

Q68. What is the access modifier of a member function of in an Interface created in .NET?
Ans. It is always public, we cant use any other modifier other than the public modifier for the member functions of an Interface.

Q69. What does the virtual keyword in C# mean?
Ans. The virtual keyword signifies that the method and property may be overridden.

Q70. How to create a new unique ID for a control?
Ans. ControlName.ID = "ControlName" + Guid.NewGuid().ToString(); //Make use of the Guid class

Q71A. What is a HashTable in .NET?
Ans. A Hashtable is an object that implements the IDictionary interface, and can be used to store key value pairs. The key may be used as the index to access the values for that index.

Q71B. What is an ArrayList in .NET?
Ans. Arraylist object is used to store a list of values in the form of a list, such that the size of the arraylist can be increased and decreased dynamically, and moreover, it may hold items of different types. Items in an arraylist may be accessed using an index.

Q72. What is the value of the first item in an Enum? 0 or 1?
Ans. 0

Q73. Can we achieve operator overloading in VB.NET?
Ans. Yes, it is supported in the .NET 2.0 version, the "operator" keyword is used.

Q74. What is the use of Finalize method in .NET?
Ans. .NET Garbage collector performs all the clean up activity of the managed objects, and so the finalize method is usually used to free up the unmanaged objects like File objects, Windows API objects, Database connection objects, COM objects etc.

Q75. How do you save all the data in a dataset in .NET?
Ans. Use the AcceptChanges method which commits all the changes made to the dataset since last time Acceptchanges was performed.

Q76. Is there a way to suppress the finalize process inside the garbage collector forcibly in .NET?
Ans. Use the GC.SuppressFinalize() method.

Q77. What is the use of the dispose() method in .NET?
Ans. The Dispose method in .NET belongs to IDisposable interface and it is best used to release unmanaged objects like File objects, Windows API objects, Database connection objects, COM objects etc from the memory. Its performance is better than the finalize() method.

Q78. Is it possible to have have different access modifiers on the get and set methods of a property in .NET?
Ans. No we can not have different modifiers of a common property, which means that if the access modifier of a property's get method is protected, and it must be protected for the set method as well.

Q79. In .NET, is it possible for two catch blocks to be executed in one go?
Ans. This is NOT possible because once the correct catch block is executed then the code flow goes to the finally block.

Q80. Is there any difference between System.String and System.StringBuilder classes?
Ans. System.String is immutable by nature whereas System.StringBuilder can have a mutable string in which plenty of processes may be performed.

Question Bunch III

Q41. How to instruct the garbage collector to collect unreferenced data?
Ans. We may call the garbage collector to collect unreferenced data by executing the System.GC.Collect() method.

Q42. How can we set the Focus on a control in ASP.NET?
Ans. txtBox123.Focus(); OR Page.SetFocus(NameOfControl);

Q43. What are Partial Classes in Asp.Net 2.0?
Ans. In .NET 2.0, a class definition may be split into multiple physical files but partial classes do not make any difference to the compiler as during compile time, the compiler groups all the partial classes and treats them as a single class.

Q44. How to set the default button on a Web Form?
Ans.

Q45.Can we force the garbage collector to run?
Ans. Yes, using the System.GC.Collect(), the garbage collector is forced to run in case required to do so.

Q46. What is Boxing and Unboxing?
Ans. Boxing is the process where any value type can be implicitly converted to a reference type object while Unboxing is the opposite of boxing process where the reference type is converted to a value type.

Q47. What is Code Access security? What is CAS in .NET?
Ans. CAS is the feature of the .NET security model that determines whether an application or a piece of code is permitted to run and decide the resources it can use while running.

Q48. What is Multi-tasking?
Ans. It is a feature of operating systems through which multiple programs may run on the operating system at the same time, just like a scenario where a Notepad, a Calculator and the Control Panel are open at the same time.

Q49. What is Multi-threading?
Ans. When an application performs different tasks at the same time, the application is said to exhibit multithreading as several threads of a process are running.2

Q50. What is a Thread?
Ans. A thread is an activity started by a process and its the basic unit to which an operating system allocates processor resources.

Q51. What does AddressOf in VB.NET operator do?
Ans. The AddressOf operator is used in VB.NET to create a delegate object to a method in order to point to it.

Q52. How to refer to the current thread of a method in .NET?
Ans. In order to refer to the current thread in .NET, the Thread.CurrentThread method can be used. It is a public static property.

Q53. How to pause the execution of a thread in .NET?
Ans. The thread execution can be paused by invoking the Thread.Sleep(IntegerValue) method where IntegerValue is an integer that determines the milliseconds time frame for which the thread in context has to sleep.

Q54. How can we force a thread to sleep for an infinite period?
Ans. Call the Thread.Interupt() method.

Q55. What is Suspend and Resume in .NET Threading?
Ans. Just like a song may be paused and played using a music player, a thread may be paused using Thread.Suspend method and may be started again using the Thread.Resume method. Note that sleep method immediately forces the thread to sleep whereas the suspend method waits for the thread to be in a persistable position before pausing its activity.

Q56. How can we prevent a deadlock in .Net threading?
Ans. Using methods like Monitoring, Interlocked classes, Wait handles, Event raising from between threads, using the ThreadState property.

Q57. What is Ajax?
Ans. Asyncronous Javascript and XML - Ajax is a combination of client side technologies that sets up asynchronous communication between the user interface and the web server so that partial page rendering occur instead of complete page postbacks.

Q58. What is XmlHttpRequest in Ajax?
Ans. It is an object in Javascript that allows the browser to communicate to a web server asynchronously without making a postback.

Q59. What are the different modes of storing an ASP.NET session?
Ans. InProc (the session state is stored in the memory space of the Aspnet_wp.exe process but the session information is lost when IIS reboots), StateServer (the Session state is serialized and stored in a separate process call Viewstate is an object in .NET that automatically persists control setting values across the multiple requests for the same page and it is internally maintained as a hidden field on the web page though its hashed for security reasons.

Q60. What is a delegate in .NET?
Ans. A delegate in .NET is a class that can have a reference to a method, and this class has a signature that can refer only those methods that have a signature which complies with the class.

Question Bunch II

Q21. What is encapsulation?
Ans. Encapsulation is the OOPs concept of binding the attributes and behaviors in a class, hiding the implementation of the class and exposing the functionality.

Q22. What is Overloading?
Ans. When we add a new method with the same name in a same/derived class but with different number/types of parameters, the concept is called overluoad and this ultimately implements Polymorphism.

Q23. What is Overriding?
Ans. When we need to provide different implementation in a child class than the one provided by base class, we define the same method with same signatures in the child class and this is called overriding.

Q24. What is a Delegate?
Ans. A delegate is a strongly typed function pointer object that encapsulates a reference to a method, and so the function that needs to be invoked may be called at runtime.

Q25. Is String a Reference Type or Value Type in .NET?
Ans. String is a Reference Type object.

Q26. What is a Satellite Assembly?
Ans. Satellite assemblies contain resource files corresponding to a locale (Culture + Language) and these assemblies are used in deploying an application globally for different languages.

Q27. What are the different types of assemblies and what is their use?
Ans. Private, Public(also called shared) and Satellite Assemblies.

Q28. Are MSIL and CIL the same thing?
Ans. Yes, CIL is the new name for MSIL.

Q29. What is the base class of all web forms?
Ans. System.Web.UI.Page

Q30. How to add a client side event to a server control?
Ans. Example... BtnSubmit.Attributes.Add("onclick","javascript:fnSomeFunctionInJavascript()");

Q31. How to register a client side script from code-behind?
Ans. Use the Page.RegisterClientScriptBlock method in the server side code to register the script that may be built using a StringBuilder.

Q32. Can a single .NET DLL contain multiple classes?
Ans. Yes, a single .NET DLL may contain any number of classes within it.

Q33. What is DLL Hell?
Ans. DLL Hell is the name given to the problem of old unmanaged DLL's due to which there was a possibility of version conflict among the DLLs.

Q34. can we put a break statement in a finally block?
Ans. The finally block cannot have the break, continue, return and goto statements.

Q35. What is a CompositeControl in .NET?
Ans. CompositeControl is an abstract class in .NET that is inherited by those web controls that contain child controls within them.

Q36. Which control in asp.net is used to display data from an xml file and then displayed using XSLT?
Ans. Use the asp:Xml control and set its DocumentSource property for associating an xml file, and set its TransformSource property to set the xml control's xsl file for the XSLT transformation.

Q37. Can we run ASP.NET 1.1 application and ASP.NET 2.0 application on the same computer?
Ans. Yes, though changes in the IIS in the properties for the site have to be made during deployment of each.

Q38. What are the new features in .NET 2.0?
Ans. Plenty of new controls, Generics, anonymous methods, partial classes, iterators, property visibility (separate visibility for get and set) and static classes.

Q39. Can we pop a MessageBox in a web application?
Ans. Yes, though this is done clientside using an alert, prompt or confirm or by opening a new web page that looks like a messagebox.

Q40. What is managed data?
Ans. The data for which the memory management is taken care by .Net runtime’s garbage collector, and this includes tasks for allocation de-allocation.

Question Bunch I

Q1. Explain the differences between Server-side and Client-side code?
Ans. Server side code will execute at server (where the website is hosted) end, & all the business logic will execute at server end where as client side code will execute at client side (usually written in javascript, vbscript, jscript) at browser end.

Q2. What type of code (server or client) is found in a Code-Behind class?
Ans. Server side code.

Q3. How to make sure that value is entered in an asp:Textbox control?
Ans. Use a RequiredFieldValidator control.

Q4. Which property of a validation control is used to associate it with a server control on that page?
Ans. ControlToValidate property.

Q5. How would you implement inheritance using VB.NET & C#?
Ans. C# Derived Class : Baseclass
VB.NEt : Derived Class Inherits Baseclass

Q6. Which method is invoked on the DataAdapter control to load the generated dataset with data?
Ans. Fill() method.

Q7. What method is used to explicitly kill a user's session?
Ans. Session.Abandon()

Q8. What property within the asp:gridview control is changed to bind columns manually?
Ans. Autogenerated columns is set to false

Q9. Which method is used to redirect the user to another page without performing a round trip to the client?
Ans. Server.Transfer method.

Q10. How do we use different versions of private assemblies in same application without re-build?
Ans.Inside the Assemblyinfo.cs or Assemblyinfo.vb file, we need to specify assembly version.
assembly: AssemblyVersion

Q11. Is it possible to debug java-script in .NET IDE? If yes, how?
Ans. Yes, simply write "debugger" statement at the point where the breakpoint needs to be set within the javascript code and also enable javascript debugging in the browser property settings.

Q12. How many ways can we maintain the state of a page?
Ans. 1. Client Side - Query string, hidden variables, viewstate, cookies
2. Server side - application , cache, context, session, database

Q13. What is the use of a multicast delegate?
Ans. A multicast delegate may be used to call more than one method.

Q14. What is the use of a private constructor?
Ans. A private constructor may be used to prevent the creation of an instance for a class.

Q15. What is the use of Singleton pattern?
Ans. A Singleton pattern .is used to make sure that only one instance of a class exists.

Q16. When do we use a DOM parser and when do we use a SAX parser?
Ans. The DOM Approach is useful for small documents in which the program needs to process a large portion of the document whereas the SAX approach is useful for large documents in which the program only needs to process a small portion of the document.

Q17. Will the finally block be executed if an exception has not occurred?
Ans.Yes it will execute.

Q18. What is a Dataset?
Ans. A dataset is an in memory database kindof object that can hold database information in a disconnected environment.

Q19. Is XML a case-sensitive markup language?
Ans. Yes.

Q20. What is an .ashx file?
Ans. It is a web handler file that produces output to be consumed by an xml consumer client (rather than a browser).

Dynamic Datatable in C#

Create DataTable Dynamically using C#

DataTable DT = new DataTable();


//Create Column

DT.Columns.Add("Column 1");
DT.Columns.Add("Column 2");
DT.Columns.Add("Column 3");

//End Column

//Create and Add New Row

DataRow DTRow= DT.NewRow();

//Inserting values to each cell in a row

DTRow[0] = "First cell";
DTRow[1] = "Second cell";
DTRow[2] = "Third cell";

DT.Rows.Add(DTRow);

DataReader and Dataset

• A DataReader works in a connected environment, whereas DataSet works in a disconnected environment.
• Dataset communicates with the dataadapter only whereas datareader communicates with the command object
• Dataset supports integeration with XML whereas Datareader doesn't support.
• We can create relations in dataset whereas we can't create relation in datareader.
• Dataset is scrollable whereas datareader is forward only record set.

DataReader :

A DataReader object represents a forward only, read only access to data from a source.

It will require you to open the connection through out and so it is not suitable for
interacting between different tiers.


Dataset:

DataSet is disconnected, in-memory representation of relational database.

It is well suited to communicate remotely as it is disconnected and changes
can be updated whenever it is required.

Fill gridview using Datareader:

SqlConnection con = new SqlConnection("server=.;database=northwind;integrated security=true");
SqlCommand com = new SqlCommand("select * from Categories", con);
SqlDataReader DR;
con.Open();
DR = com.ExecuteReader(CommandBehavior.CloseConnection);
DR.Read();
GridView1.DataSource = DR;
GridView1.DataBind();

Fill gridview using DataSet:

SqlConnection con = new SqlConnection("server=.;database=northwind;integrated security=true");
SqlDataAdapter DA = new SqlDataAdapter("select * from Categories", con);
DataSet DS = new DataSet();
DA.Fill(DS);
GridView1.DataSource = DS;
GridView1.DataBind();

openFileDialog c#

OpenFileDialog openFileDialogX = new OpenFileDialog();
string Fname, Fext,fpath ;
int Fsize;

private void GetOpenFileDialog()
{
openFileDialogX.CheckPathExists = true;
openFileDialogX.Filter = "Image Files (*.bmp;*.jpg;*.jpeg)|*.bmp;*.jpg;*.jpeg|" + "PNG files (*.png)|*.png|text files (*.text)|*.txt|doc files (*.doc)|*.doc|pdf files (*.pdf)|*.pdf|excel files(*.xls)|*.xls|excel files07(*.xlsx)|*.xlsx";
openFileDialogX.Multiselect = false;
openFileDialogX.AddExtension = true;
openFileDialogX.ValidateNames = true;
openFileDialogX.InitialDirectory = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
openFileDialogX.ShowDialog();
fpath = openFileDialogX.FileName.ToString();
fname=System.IO.Path.GetFileName(openFileDialogX.FileName).ToUpper();
Fsize = openFileDialogX.FileName.Length;
Fext = System.IO.Path.GetExtension(Fname);
}

access specifiers in C# and VB.Net

Public, Private, Protected, Friend, Internal, Default


1. PUBLIC
As the name specifies, it can be accessed from anywhere. If a member of a class is defined as public then it can be accessed anywhere in the class as well as outside the class. This means that objects can access and modify public fields, properties, methods.

2. PRIVATE
As the name suggests, it can't be accessed outside the class. Its the private property of the class and can be accessed only by the members of the class.

3. FRIEND/INTERNAL
Friend & Internal mean the same. Friend is used in VB.NET. Internal is used in C#. Friends can be accessed by all classes within an assembly but not from outside the assembly.

4. PROTECTED
Protected variables can be used within the class as well as the classes that inherites this class.

5. PROTECTED FRIEND/PROTECTED INTERNAL
The Protected Friend can be accessed by Members of the Assembly or the inheriting class, and ofcourse, within the class itself.

6. DEFAULT
A Default property is a single property of a class that can be set as the default. This allows developers that use your class to work more easily with your default property because they do not need to make a direct reference to the property. Default properties cannot be initialized as Shared/Static or Private and all must be accepted at least on argument or parameter. Default properties do not promote good code readability, so use this option sparingly.

difference between ADO and ADO.NET

• ADO works with connected data. This means that when you access data, such as viewing and updating data, it is real-time, with a connection being used all the time.

• The ADO.NET object is a lightweight object. The ADO Recordset was a huge object in ADO.
• ADO.NET breaks the functionality of the ADO object to multiple classes, thereby allowing a focused approach to developing code.
• The ADO.NET DataReader is equivalent to the "firehose" cursor.
• The DataSet is a disconnected cache with tracking and control binding functionality.
• The DataAdapter provides the ability to completely customize how the central data store is updated with the changes to a DataSet.
• ADO allows you to create client-side cursors only, whereas ADO.NET gives you the choice of either using client-side or server-side cursors.
• ADO allows you to persist records in XML format, ADO.NET allows you to manipulate your data using XML as the primary means.

difference between Classic ASP and ASP.NET

Major difference:

* Classic ASP is Interpreted. ASP.NET is Compiled. If code is changed, ASP.NET recompiles,
otherwise does'nt.

*Classic ASP uses a technology called ADO to connect and work with databases. ASP.NET uses the ADO.NET technology (which is the next generation of ADO).

Others:

* In classic ASP, there was no server controls. You have to write all html tags manually. ASP.NET offers a very rich set of controls called Server Controls and Html Controls.

*Validation Controls.

*Debugging benefits-In classic ASP, debugging is a tough task because of limited support due to the interpreted model. In contrast, not only ASP.NET improves the performance over the interpreted model but also provides debugging tools for component developers and pages compiled into classes.

*Multi Language Support-Only VBScript and Javascript were available for scripting in ASP where as, in ASP.NET there are no such restrictions. The .NET compliant language can be used with ASP.NET including several like C# and VB.NET, where both of them are server-sided languages.