Interview Question(Asp.net)

1.    What is ASP?
Active Server Pages (ASP), also known as Classic ASP, is a Microsoft's server-side technology, which helps in creating dynamic and user-friendly Web pages. It uses different scripting languages to create dynamic Web pages, which can be run on any type of browser. The Web pages are built by using either VBScript or JavaScript and these Web pages have access to the same services as Windows application, including ADO (ActiveX Data Objects) for database access, SMTP (Simple Mail Transfer Protocol) for e-mail, and the entire COM (Component Object Model) structure used in the Windows environment. ASP is implemented through a dynamic-link library (asp.dll) that is called by the IIS server when a Web page is requested from the server.
2.    What is ASP.NET?
ASP.NET is a specification developed by Microsoft to create dynamic Web applications, Web sites, and Web services. It is a part of .NET Framework. You can create ASP.NET applications in most of the .NET compatible languages, such as Visual Basic, C#, and J#. The ASP.NET compiles the Web pages and provides much better performance than scripting languages, such as VBScript. The Web Forms support to create powerful forms-based Web pages. You can use ASP.NET Web server controls to create interactive Web applications. With the help of Web server controls, you can easily create a Web application.
3.    What is the basic difference between ASP and ASP.NET?
The basic difference between ASP and ASP.NET is that ASP is interpreted; whereas, ASP.NET is compiled. This implies that since ASP uses VBScript; therefore, when an ASP page is executed, it is interpreted. On the other hand, ASP.NET uses .NET languages, such as C# and VB.NET, which are compiled to Microsoft Intermediate Language (MSIL).
4.    In which event are the controls fully loaded?
Page load event guarantees that all controls are fully loaded. Controls are also accessed in Page_Initevents but you will see that view state is not fully loaded during this event
5.    How can we identify that the Page is Post Back?
Page object has an "IsPostBack" property, which can be checked to know that is the page posted back.
6.    What is the lifespan for items stored in ViewState?
The items stored in ViewState live until the lifetime of the current page expires including the postbacks to the same page.
7.    How information about the user's locale can be accessed?
The information regarding a user's locale can be accessed by using the System.Web.UI.Page.Cultureproperty.

7.    What is the difference between SQL notification and SQL invalidation?
The SQL cache notification generates notifications when the data of a database changes, on which your cache item depends. The SQL cache invalidation makes a cached item invalid when the data stored in a SQL server database changes.
8.    Which is the parent class of the Web server control?
The System.Web.UI.Control class is the parent class for all Web server controls.
9.    Can you set which type of comparison you want to perform by the CompareValidator control?
Yes, by setting the Operator property of the CompareValidator control.
10.  What is the behavior of a Web browser when it receives an invalid element?
The behavior of a Web browser when it receives an invalid element depends on the browser that you use to browse your application. Most of the browsers ignore the invalid element; whereas, some of them display the invalid elements on the page.
11.  What are the advantages of the code-behind feature?
The code-behind feature of ASP.NET offers a number of advantages:
§  Makes code easy to understand and debug by separating application logic from HTML tags
§  Provides the isolation of effort between graphic designers and software engineers
§  Removes the problems of browser incompatibility by providing code files to exist on the Web server and supporting Web pages to be compiled on demand
13.  What is object-oriented programming (OOP)?
OOP is a technique to develop logical modules, such as classes that contain properties, methods, fields, and events. An object is created in the program to represent a class. Therefore, an object encapsulates all the features, such as data and behavior that are associated to a class. OOP allows developers to develop modular programs and assemble them as software. Objects are used to access data and behaviors of different software modules, such as classes, namespaces, and sharable assemblies. .NET Framework supports only OOP languages, such as Visual Basic .NET, Visual C#, and Visual C++.
14.  What is a class?
A class describes all the attributes of objects, as well as the methods that implement the behavior of member objects. It is a comprehensive data type, which represents a blue print of objects. It is a template of object.

A class can be defined as the primary building block of OOP. It also serves as a template that describes the properties, state, and behaviors common to a particular group of objects.

A class contains data and behavior of an entity. For example, the aircraft class can contain data, such as model number, category, and color and behavior, such as duration of flight, speed, and number of passengers. A class inherits the data members and behaviors of other classes by extending from them.
15.  What is an object?
They are instance of classes. It is a basic unit of a system. An object is an entity that has attributes, behavior, and identity. Attributes and behavior of an object are defined by the class definition.
16.  What is the relationship between a class and an object?
A class acts as a blue-print that defines the properties, states, and behaviors that are common to a number of objects. An object is an instance of the class. For example, you have a class called Vehicleand Car is the object of that class. You can create any number of objects for the class named Vehicle, such as VanTruck, and Auto.

The 
new operator is used to create an object of a class. When an object of a class is instantiated, the system allocates memory for every data member that is present in the class.
17.  Explain the basic features of OOPs.
The following are the four basic features of OOP:


·         Abstraction - Refers to the process of exposing only the relevant and essential data to the users without showing unnecessary information.
·         Polymorphism - Allows you to use an entity in multiple forms.
·         Encapsulation - Prevents the data from unwanted access by binding of code and data in a single unit called object.
·         Inheritance - Promotes the reusability of code and eliminates the use of redundant code. It is the property through which a child class obtains all the features defined in its parent class. When a class inherits the common properties of another class, the class inheriting the properties is called a derived class and the class that allows inheritance of its common properties is called a base class.
18.  What is the difference between arrays and collection?
Array:


1.    You need to specify the size of an array at the time of its declaration. It cannot be resized dynamically.
2.    The members of an array should be of the same data type.

Collection:


3.    The size of a collection can be adjusted dynamically, as per the user's requirement. It does not have fixed size.
4.    Collection can have elements of different types.

19.  What are collections and generics?
A collection can be defined as a group of related items that can be referred to as a single unit. TheSystem.Collections namespace provides you with many classes and interfaces. Some of them are -ArrayListListStackICollectionIEnumerable, and IDictionary. Generics provide the type-safety to your class at the compile time. While creating a data structure, you never need to specify the data type at the time of declaration. The System.Collections.Generic namespace contains all the generic collections.
20.  How can you prevent your class to be inherited further?
You can prevent a class from being inherited further by defining it with the sealed keyword.
21.  What is the index value of the first element in an array?
In an array, the index value of the first element is 0 (zero).
22.  Can you specify the accessibility modifier for methods inside the interface?
All the methods inside an interface are always public, by default. You cannot specify any other access modifier for them.
23.  Is it possible for a class to inherit the constructor of its base class?
No, a class cannot inherit the constructor of its base class.
24.  How is method overriding different from method overloading?
Overriding involves the creation of two or more methods with the same name and same signature in different classes (one of them should be parent class and other should be child).

Overloading is a concept of using a method at different places with same name and different signatures within the same class.
25.  What is the difference between a class and a structure?
Class:


1.    A class is a reference type.
2.    While instantiating a class, CLR allocates memory for its instance in heap.
3.    Classes support inheritance.
4.    Variables of a class can be assigned as null.
5.    Class can contain constructor/destructor.

Structure:


6.    A structure is a value type.
7.    In structure, memory is allocated on stack.
8.    Structures do not support inheritance.
9.    Structure members cannot have null values.
10.  Structure does not require constructor/destructor and members can be initialiazed automatically.
26.  What are similarities between a class and a structure.
Structures and classes are the two most important data structures that are used by programmers to build modular programs by using OOP languages, such as Visual Basic .NET, and Visual C#. The following are some of the similarities between a class and a structure:


·         Access specifiers, such as publicprivate, and protected, are identically used in structures and classes to restrict the access of their data and methods outside their body.
·         The access level for class members and struct members, including nested classes and structs, is private by default. Private nested types are not accessible from outside the containing type.
·         Both can have constructors, methods, properties, fields, constants, enumerations, events, and event handlers.
·         Both structures and classes can implement interfaces to use multiple-inheritance in code.
·         Both structures and classes can have constructors with parameter.
·         Both structures and classes can have delegates and events.
27.  What is a multicast delegate?
Each delegate object holds reference to a single method. However, it is possible for a delegate object to hold references of and invoke multiple methods. Such delegate objects are called multicast delegates or combinable delegates.
28.  Can you declare an overridden method to be static if the original method is not static?
No. Two virtual methods must have the same signature.
29.  Why is the virtual keyword used in code?
The virtual keyword is used while defining a class to specify that the methods and the properties of that class can be overridden in derived classes.
30.  Can you allow a class to be inherited, but prevent a method from being overridden in C#?
Yes. Just declare the class public and make the method sealed.




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