Q & A

Some Common .NET and SQL Server Interview Questions and Answers

Agile software development refers to a group of software development methodologies based on iterative development, where requirements and solutions evolve through collaboration between self-organizing cross-functional teams. The term was coined in the year 2001 when the Agile Manifesto was formulated.

Agile methods generally promote a disciplined project management process that encourages frequent inspection and adaptation, a leadership philosophy that encourages teamwork, self-organization and accountability, a set of engineering best practices intended to allow for rapid delivery of high-quality software, and a business approach that aligns development with customer needs and company goals. Conceptual foundations of this framework are found in modern approaches to operations management and analysis, such as lean manufacturing, soft systems methodology, speech act theory (network of conversations approach), and Six Sigma.

Method overloading means having two or more methods with the same name but different signatures in the same scope. These two methods may exist in the same class or another one in base class and another in derived class.

Method overriding means having a different implementation of the same method in the inherited class. These two methods would have the same signature, but different implementation. One of these would exist in the base class and another in the derived class. These cannot exist in the same class.

'Three-tier' is a client-server architecture in which the user interface,functional process logic ("business rules"), computer data storage and data access are developed and maintained as independent modules, most often on separate platforms.

The three-tier model is considered to be[weasel words] a software architectureand a software design pattern.

Apart from the usual advantages of modular software with well defined interfaces, the three-tier architecture is intended to allow any of the three tiers to be upgraded or replaced independently as requirements or technologychange. For example, a change of operating system in the presentation tierwould only affect the user interface code.

Typically, the user interface runs on a desktop PC or workstation and uses a standard graphical user interface, functional process logic may consist of one or more separate modules running on a workstation or application server, and an RDBMS on a database server or mainframe contains the computer data storage logic. The middle tier may be multi-tiered itself (in which case the overall architecture is called an "n-tier architecture").

Three-tier architecture has the following three tiers:

Presentation tier

This is the topmost level of the application. The presentation tier displays information related to such services as browsing merchandise, purchasing, and shopping cart contents. It communicates with other tiers by outputting results to the browser/client tier and all other tiers in the network.

Application tier (Business Logic/Logic Tier/Data Access Tier/Middle Tier)

The logic tier is pulled out from the presentation tier and, as its own layer, it controls an application’s functionality by performing detailed processing.

Data tier

This tier consists of Database Servers. Here information is stored and retrieved. This tier keeps data neutral and independent from application servers or business logic. Giving data its own tier also improves scalability and performance.

Storing this SQL select statement as a stored procedure is good because:
You only need to write the procedure once, and you can then access it very simply just by using its name. Imagine if this was a complicated select command. Using just its name is like using a short-cut.
6. What are static variables?

Variables declared static are commonly shared across all instances of a class. Only static variables exist before objects are created
7. What is the Difference between interface and abstract class?
An Abstract Class can contain default Implementation, where as an Interface should not contain any implementation at all. An Interface should contain only definitions but no implementation. where as an abstract class can contain abstract and non-abstract methods. When a class inherits from an abstract, the derived class must implement all the abstract methods declared in the base class. an abstract class can inherit from another non-abstract class.

-abstract class can not be instantiated, interface can be instantiated.

-interface only contains the declaration of the method.

C# doesn't support multiple inheritance, so there's no way to have a given class selectively derive from multiple classes. The answer is interfaces. Interfaces give you the ability to define a set of semantically related methods and properties that selected classes can implement regardless of the class hierarchy.

An interface contains only the signatures of methods, delegates or events. The implementation of the methods is done in the class that implements the interface.

8. What's an Interface?

An interface is a reference type object with no implementation. You can think of it as an abstract class with all the implementation stripped out and everything that is not public removed. Abstract classes are classes that can not be instantiated. No properties or methods are actually coded in an interface, they are only defined. So the interface doesn't actually do anything but only has a signature for interaction with other classes or interfaces. A good analogy for an interface is a pencil and a pencil sharpener. When we talk of a pencil and a pencil sharpener we generally know what they do and how they interact. We don't have to know the inner workings of a particular sharpener or pencil, only how to use them through their interface.

public interface IPencil
{
void Write();
bool IsSharp { get; }
}

public interface IPencilSharpener
{
void Sharpen(IPencil pencil);
}
10. What is the Main Method in C#?

Entry Point in C# program

The first function to be called in any C#program is Main. We can have as many as four different ways to declareMain in our program. They are as follows:

static void Main() {…}
static int Main() {…}
static void Main(string[] a) {…}
static int Main(string[] args) {…}

note :- String and string words are similar to use. They are alias!

The operating system calls Main and waits for it to return a value. This value denotes the success or failure of the program.

Main can either return a number or result inno return value, that is, void. If it returns an int, by convention, avalue of zero means success and any other value indicates an error. Nointernational authority can standardize the error numbers, it largelydepends on the programmer himself.

Java programs start executing at the main method, which has the following method heading: public static void main(String[] args)
public static void main(String... args)
public static void main(String args[5])
11. What is a delegate?

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

· 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 Co-variance and Contravariance
12. What is a thread?
13. Explain Having clause in SQL

The HAVING clause is used in combination with the GROUP BY clause. It can be used in a SELECT statement to filter the records that a GROUP BY returns.

The syntax for the HAVING clause is:

SELECT column1, column2, ... column_n, aggregate_function (expression)
FROM tables
WHERE predicates
GROUP BY column1, column2, ... column_n
HAVING condition1 ... condition_n;
14. What is a Concrete class?

An abstract class is meant to be used as the base class from which other classes are derived. The derived class is expected to provide implementations for the methods that are not implemented in the base class. A derived class that implements all the missing functionality is called a concrete class.
15. What is JavaScript? 
16. What is AJAX? 
19. What is a Session?

Session is server side state management technique
Putting the state in a server-side database
Very secure
Everything kept on server - browser sees only what it needs
Cookie/URL only used to store session ID; hard to guess IDs
Cannot be blocked by client (since it’s on the server)
Can use an in-memory database for speed
Can store lots of data and keep it in original (object) form
Scalability issues: server must store state of all clients
Potentially millions of Web clients = serious load on server
Must use timeouts to detect and clean up dead sessions
Client browser won’t tell you when it is exiting
The default behavior is to store session variables in the memory space of theASP.NET worker process
20. What is a Web Service? 

A web service is typically an application programming interface (API) or Web API that is accessed via Hypertext Transfer Protocol (HTTP) and executed on a remote system, hosting the requested service. Web services tend to fall into one of two camps: big web services and RESTful web services.

21. What is polymorphism? 

Generally, the ability to appear in many forms. In object-oriented programming, polymorphism refers to a programming language's ability to process objects differently depending on their data type or class. More specifically, it is the ability to redefine methods for derived classes. For example, given a base class shape, polymorphism enables the programmer to define different area methods for any number of derived classes, such as circles, rectangles and triangles. No matter what shape an object is, applying the area method to it will return the correct results. Polymorphism is considered to be a requirement of any true object-oriented programming language (OOPL).
23. What is SOAP?

SOAP is a lightweight protocol for exchange of information in a decentralized, distributed environment. It is an XML based protocol that consists of three parts: an envelope that defines a framework for describing what is in a message and how to process it, a set of encoding rules for expressing instances of application-defined datatypes, and a convention for representing remote procedure calls and responses. SOAP can potentially be used in combination with a variety of other protocols; however, the only bindings defined in this document describe how to use SOAP in combination with HTTP and HTTP Extension Framework.

* XHTML elements must be properly nested* XHTML elements must always be closed
* XHTML elements must be in lowercase
* XHTML documents must have one root element
* Attribute names must be in lower case
* Attribute values must be quoted
* Attribute minimization is forbidden
* The id attribute replaces the name attribute
* The XHTML DTD defines mandatory elements
25. What is the difference between .NET remoting and Webservices?

Web service can be accessed only over http protocol but .net remoting can be accessed over
TCP,HTTP ,SMTP etc.Web service are stateless architechture but .net remoting support stateful
and state less environment.Dot net remoting provides fast communication than web service when use tcp
channel and binary formatter.web service is easy to create and deploy but .net remoting bit
complex to program.Web service can be cross platform and open protocol.remoting is tight
coupled and web service for disconnected loosely coupled.

Unified Modeling Language (UML) is a standardized general-purpose modeling language in the field of object-oriented software engineering. The standard is managed, and was created, by the Object Management Group. It was first added to the list of OMG adopted technologies in 1997, and has since become the industry standard for modeling software-intensive systems.

A DataSet if the bucket here; it allows you to carry around a disconnected set of data and work with it - but you need to incur the cost of carrying the bucket (so best to keep it to a size you are comfortable with).

A data-reader is the hose: it provides one-way/once-only access to data as it flies past you; you don't have to carry all of the available water at once, but it needs to be connected to the tap/database.

And in the same way that you can fill a bucket with a hose, you can fill the DataSet with the data-reader.

28. what is an asynchronous call?

A function that enables processing to continue without waiting for the function to return a value.

29. REST Web Service