Most Important Interview Questions(OOP, Asp.NET, PHP)

Execute scalar is a Single value single column.

Execute Reader is a Read only forward only.

Execute Non Query is used for Insert, Update, and Delete Statements.

With examples………

Run time Master page generate?

Hi, it is possible to change Theme and Masterpage dynamically.

But they have to be done on Page_Preinit Event like this

page.masterpagefile ="~/SecondMaster.master"

page.Theme = "SecondDefaultTheme"

What is Virtual Method in .Net?

By declaring base class function as virtual, we allow the function to be overridden in any of derived class.

Example of Virtual Method in .Net:

Class parent
{
virtual void hello()
{ Console.WriteLine(“Hello from Parent”); }
}

Class child : parent
{
override void hello()
{ Console.WriteLine(“Hello from Child”); }
}

static void main()
{
parent objParent = new child();
objParent.hello();
}

//Output
Hello from Child.

What is polymorphism?

It is the important concept of OOP, from the greek concept 'poly' means many 'morphism' means form ,from this the definition  is "the ability to take more than one form"

EXAMPLE:

method overloading (static polymorphism...early binding)

method overriding (dynamic polymorphism...late binding)

Abstract class?

Virtual functions?

Diff b/w View and Control states?

Entity framework?

LINQ queries?

Sessions? http://www.deliciousdotnet.com/2011/03/sessions-in-aspnet-how-to-use-session.html

How to get largest number from comma separated string using function, using Asp.Net?

How to get Uppercase Letter in Comma separated array?

What is MVC, and how to implement Action Result in MVC?

All SQL joins?

Hypertext, Hyperlink?

Diff b/w Datatable and DataReader?

Diff b/w Div & Span?

How to get 2^nd largest record from table field (Query)?

Passing through reference and passing through object?

Enum: Enums store special values. They make programs simpler. If you place constants directly where used, your C# program becomes complex. It becomes hard to change. Enums instead keep these magic constants in a distinct type. They improve code clarity. http://www.dotnetperls.com/enum

What is the difference between shadowing and overriding

Shadowing - Protecting against a subsequent base class modification that introduces a member you have already defined in your derived class
Overriding - Achieving polymorphism by defining a different implementation of a procedure or property with the same calling sequence

What is Polymorphism in OOPS?

·         Polymorphism is one of the primary characteristics (concept) of object-oriented programming

·         Poly means many and morph means form. Thus, polymorphism refers to being able to use many forms of a type without regard to the details

·         Polymorphism is the characteristic of being able to assign a different meaning specifically, to allow an entity such as a variable, a function, or an object to have more than one form

·         Polymorphism is the ability to process objects differently depending on their data types

·         Polymorphism is the ability to redefine methods for derived classes.

Delegates

A delegate is a type that references a method. Once a delegate is assigned a method, it behaves exactly like that method. The delegate method can be used like any other method, with parameters and a return value, as in this example:

C#

public delegate int PerformCalculation(int x, int y);

Any method that matches the delegate's signature, which consists of the return type and parameters, can be assigned to the delegate. This makes is possible to programmatically change method calls, and also plug new code into existing classes. As long as you know the delegate's signature, you can assign your own delegated method.

This ability to refer to a method as a parameter makes delegates ideal for defining callback methods. For example, a sort algorithm could be passed a reference to the method that compares two objects. Separating the comparison code allows the algorithm to be written in a more general way.

Delegates Overview

Delegates have the following properties:

·         Delegates are similar to C++ function pointers, but are type safe.

·         Delegates allow methods to be passed as parameters.

·         Delegates can be used to define callback methods.

·         Delegates can be chained together; for example, multiple methods can be called on a single event.

·         Methods don't need to match the delegate signature exactly. For more information, see Covariance and Contravariance

Interfaces in C#

An interface in C# is simply a template for a class. It’s part of how C# implements polymorphism.  An interface doesn’t contain any code, only definitions of methods, properties, events and indexers. A class that implements an interface will need to define the code used for these items. Here’s a short code snippet of an example C# interface…

public interface IMyItem

{

    int Id { get; set; }

    string Description { get; set; }

    string RunTest(int testNumber);

    event EventHandler TestStatus;

    string this[int index] { get; set;}

}

In this example, the interface includes two properties, a method, an event and an indexer. A class that used this interface would need to provide code for these items. While the code doesn’t have to do anything, it does have to be implemented by the class using the interface.

One powerful thing that you can do with interfaces is that you can have a class that implements more than one interface. One of my favorite usages is to not only implement a program specific interface but to also implement a generic List or Queue.

Abstract Classes in C#

An abstract class in C# is a class that can’t be instantiated and, like an interface, is intended to provide a common class definition that is shared by derived classes. Like an interface, the routines in an abstract class may be methods, properties, indexers and events. Unlike an interface, an abstract class may contain code although it may also have abstract methods that do not have code. Also, an abstract class may define constructors and destructors while an interface does not as well as internal private and protected variables.

Here’s a simple example of a C# abstract class…

public abstract class TestItem

{

    private int _testId;

    public TestItem(int testIdValue)

    {

        _testId = testIdValue;

    }

    public int TestId

    {

        get

        {

            return _testId;

        }

        set

        {

            _testId = value;

        }

    }

    public abstract string Description { get; set; }

    public abstract void RunTest(int i);

    public abstract string this[int index] { get; set; }

}

Write a C program to swap two variables without using a temporary variable.

This method is also quite popular
a=a+b;
b=a-b;
a=a-b;

What is heap and stack?



The stack is a place in the computer memory where all the variables that are declared and initialized before runtime are stored. The heap is the section of computer memory where all the variables created or initialized at runtime are stored.

Swapping three variable without using temp variable 

a = 2 b = 1 c = 3 

a = a+b+c = 6

b = a -b-c = 2 
c = a -b- c = 1
a = a-b-c = 3 

After swapping 

a = 3 ; b = 2 ; c = 1

What is the difference between UserControl, WebControl?

UserControl: A custom control, ending in .ascx, that is composed of other web controls. Its almost like a small version of an aspx webpage. It consists of a UI (the ascx) and codebehind. Cannot be reused in other projects by referencing a DLL.

WebControl: A control hosted on a webpage or in a UserControl. It consists of one or more classes, working in tandem, and is hosted on an aspx page or in a UserControl. WebControls don't have a UI "page" and must render their content directly. They can be reused in other applications by referencing their DLLs.

base keyword 

The base keyword is used to access members of the base class from within a derived class:

• Call a method on the base class that has been overridden by another method.
• Specify which base-class constructor should be called when creating instances of the derived class.

Authentication types in web.config?

URL: http://msdn.microsoft.com/en-us/library/aa291347(v=vs.71).aspx

ASP.NET implements additional authentication schemes using authentication providers, which are separate from and apply only after the IIS authentication schemes. ASP.NET supports the following authentication providers:

• Windows (default)
• Forms
• Passport
• None

To enable an authentication provider for an ASP.NET application, use the authentication element in either machine.config or Web.config as follows:

Each ASP.NET authentication provider supports an OnAuthenticate event that occurs during the authentication process, which you can use to implement a custom authorization scheme. The primary purpose of this event is to attach a custom object that implements the IPrincipal Interface to the context.

IsPOSTback function in Asp.Net?

URL: Is Postback is normally used on page _load event to detect if the page is getting generated due to postback requested by a control on the page or if the page is getting loaded for the first time. IsPostBack is a Boolean property of a page when is set (=true) when a page is first loaded. Thus, the first time that the page loads the IsPostBack flag is false and for subsequent PostBacks, it is true. Each time a PostBack occurs, the entire page including the Page_Load is ‘posted back‘and executed.

ASP.NET: Difference between Server.Transfer and response.Redirect?

In response.redirect the browser url changes to targeted page as well as in server.transfer the url remains same!

Response.Redirect should be used when:

·         we want to redirect the request to some plain HTML pages on our server or to some other web server

·         we don't care about causing additional roundtrips to the server on each request

·         we do not need to preserve Query String and Form Variables from the original request

·         we want our users to be able to see the new redirected URL where he is redirected in his browser (and be able to bookmark it if its necessary)

Server.Transfer should be used when:

·         we want to transfer current page request to another .aspx page on the same server

·         we want to preserve server resources and avoid the unnecessary roundtrips to the server

·         we want to preserve Query String and Form Variables (optionally)

·         we don't need to show the real URL where we redirected the request in the users Web Browser

Round-trip – Response.Redirect() first sends request for new page to the browser, then browser sends that request to the web-server, and after that your page changes. But Server.Transfer() directly communicate with the server to change the page hence it saves an extra  round-trip (to the browser) in the whole process.

Difference Between Web.Config file and Global.asax ?

Web.Config file is used.... 



1. To specify the application settings 

2. To specify the session mechanism available to use for that application. 

3. To Specify the Connection strings. 

4. To Specify the authentication and authorization. 

5. To Specify the http handlers. 

6. To Specify different providers. 



Global.asax file is used to specify the session and application event handlers. which is handling application level events and session level events..

Advantages and Disadvantages of Session

Advantages: 

* It helps to maintain user states and data to all over the application.
* It can easily be implemented and we can store any kind of object. 
* Stores every client data separately. 
* Session is secure and transparent from user.

Disadvantages: 

* Performance overhead in case of large volume of user, because of session data stored in server memory.
* Overhead involved in serializing and De-Serializing session Data. Because In case of StateServer and SQLServer session mode we need to serialize the object before store.

ADO.Net encapsulates our queries and commands to provide a uniform access to various database management systems. ADO.Net is a successor of ADO (ActiveX Data Object). The prime features of ADO.Net are its disconnected data access architecture and XML integration.

Access Data Object simply stood for "ADO". EXTENSION OF ADO.NET is Activex Data Object . main use of capturing datasource for bridge between the application layer to the database layer. in other words interaction between application to database with proper connection string under configurations

What is indexing?

Indexing is a way of sorting a number of records on multiple fields. Creating an index on a field in a table creates another data structure which holds the field value, and pointer to the record it relates to. This index structure is then sorted, allowing Binary Searches to be performed on it.

TRIGGERS

A Trigger is a named database object which defines some action that the database should take when some databases related event occurs. Triggers are executed when you issues a data manipulation command like INSERT, DELETE, UPDATE on a table for which the trigger has been created. They are automatically executed and also transparent to the user. But for creating the trigger the user must have the CREATE TRIGGER privilege. In this section we will describe you about the syntax to create and drop the triggers and describe you some examples of how to use them.

CREATE TRIGGER

The general syntax of CREATE TRIGGER is :
  CREATE TRIGGER trigger_name trigger_time trigger_event ON tbl_name FOR EACH ROW trigger_statement

What are the differences between final, finally, finalize Methods?

final is a keyword. It’s constant. It can’t be changed from its initiated value.

finally() method used exception handling concept.finally() block will execute whether or not try block can be execute. It’s used to close a file.

finalize is used when an object is just before deleted, it can be used in garbage collection.

Accessing Arrays

We can access an array item by passing the item index in the array. The following code snippet creates an array of three items and displays those items on the console.

// Initialize a fixed array one item at a time

int[] staticIntArray = new int[3];

staticIntArray[0] = 1;

staticIntArray[1] = 3;

staticIntArray[2] = 5;

// Read array items one by one

Console.WriteLine(staticIntArray[0]);

Console.WriteLine(staticIntArray[1]);

Console.WriteLine(staticIntArray[2]);

http://www.c-sharpcorner.com/uploadfile/mahesh/workingwitharrays11232005064036am/workingwitharrays.aspx