OOPS FAQ's

 Updated on October 16, 2014     VIKRAM     861

Q: What is the difference between object based programming and object oriented programming?

Ans:

  • If the programming methodology supports encapsulation,Inheritance and polymorphiam then, it is called object oriented programming language, it supports code extendability.
  • If the programming methodology supports only encapsulation then, it is called object based programming language, it supports code extendability.

Q: What are the fundamental concepts of oops?

Ans:

  • Encapsuplation
  • Inheritance
  • Polymorphism

Q: What is encapsulation and its advantage?

Ans: Grouping related thing together is called Encapsulation, we can acheive Portabily.

Q: How to implement the encapsulation in c#?

Ans: By using class,struct,properties,interface etc.

Q: What is DataHiding ?

Ans: Hiding unnecessary details from the user.

Q: What is the Advantage of DataHiding ?

Ans: Due to DataHiding behavior of the product can be protected, so that developers logic can be secured.

Q: What is Abstraction ?

Ans: Hiding complete implementation details from the user is called abstraction.
Due to abstraction user will feel comfortable while working with the product.

Q: Difference between DataHiding and Abstraction ?

Ans:

  • DataHiding: Hiding unnecessary data from the user, programmer is benifited.
  • Abstraction: Hiding complete implementation details from the user, user is benifited.

Q: What is Class ?

Ans: Class is a model or template regarding the thing.

Q: What is an Object ?

Ans: An instance of the class.

Q: What is the difference between Encapsulation and Class ?

Ans:

  • Encapsulation: Is a objcet oriented programming concept.
  • Class: it is a feature of the language by which we can implement encapsulation.

Q: What is the default access modifier for the class?

Ans: Internal

Q: What is the default access modifier for the members of the class?

Ans: Private

Q: What is the default access modifier for the members of the struct?

Ans: Private

Q: Difference between Class and Struct ?

Ans:

Class Struct
1. Class is Object type 1. Struct is Value type
2.  All accessmodifiers are allowed 2. Protected is not supported
3. Inheritance is possible 3. Not possible
4. Supports all types of constructors 4. Default Constructor is not supported
5. Distructor allowed 5. Not allowed
6. method overriding possible 6. Not possible

Q: What is Accessor Method and Mutator method ?

Ans:

  • Accessor Method: Any of the method is defined to access the value from the  instance variable.
  • Mutator Method: Any of the method is defined to modify the value from the  instance variable.

Q: What is the use of base keyword ?

Ans: To access the base class members in the derived class we can use base keyword. (or) To invoke the base class constructor from the derived calss constructor.

Q: What is the difference between property and indexer ?

Ans:

  • If we use property we can get and modify the values from the instance variables .
  • By using indexer we can access the object by applying subscript with index position.

Q: What is Constructor ?

Ans: Constructor is a special method in the class, which is used to initialize the instance variables to some meaning full initial values, when the class is instantiated.

Q: Why the name of Constructor and class is same ?

Ans: For easy identification purpose of the compiler.

Q: Can we overload distructor() ?

Ans: No, because it is parameter less.

Q: What is namespace ?

Ans: NameSpace is a logical container. Where in we can find classes, enumerations, interfaces delegates.

Q: What is the purpose of namespace?

Ans: To avoid the name collisions.

Q: What is the difference between namespace and class ?

Ans:

  • Namespace is used to avoid the name collisions
  • Class is used to implement encapsulation.

Q: What is the alias name for namespaces and when it is required?

Ans: When ever there is a conflict among the members in the included namespaces, then we can avoid it by providing alias nameto the member where there is a conflict.

Q: What is the purpose of params keyword ?
 

Ans: Params keyword is used to specify the array of parameters to the method.

Q: What is the difference between out and ref parameters ?

Ans:

  • Out parameters are write only parameters in side the method.
  • Ref parameters are read - write parameters in side the method.

Q: What is Binding ?

Ans: Replacing method invokation with its appropriate base reference is called Binding.

Q: What is static Binding ?

Ans: If the binding process is carried out at the time of compilation is called Static bonding.

Q: What is Dynamic binding ?

Ans: If the binding process is carried out at the run time is called Dynamic bonding.

Q: What are the difference between Method overloding and overriding ?

Ans:

Overloding  Overriding
1. Nothing but no.of methods defined with the same name by showing the difference in signature part 1. Nothing but no.of methods defined with same name and same signature
2.  Possible with in the same class and derived class 2. Possible in the derived class by the override keyword
3. Possible for static, non-static methods 3. Possible for only abstract and virtual methods

Q: What is polymorphism ?

Ans: Performing different actions by invoking same invocation.

Q: What is the diff between abstract calss and interface ?

Ans:

Abstract class Interface
1. partially unimplemented 1. Fully unimplipmented
2. Complete abstraction is not possible 2. Complete abstraction is possble
3. All the types of members are allowed 3. Onlymethods,properties,indexers and events are allowed

Q: What is sealed class ?

Ans: If a class is declared as sealed calss, then it can not be inherited ex: Thread class.

Q: What is extension method?

Ans:

  • From c# 3.0 we can find this.
  • We can extend the functionality of existing data type by defining extension method.
  • Always extension methos must be declared as static and defined in static class.

Q: What is the use of Dispose Method()?

Ans: It is used to Invoke the Garbage collector dynamically.

Q: What is the difference between string and stringBuilder?

Ans:

  • String: String class objects will return another instance of the string for each operation.
  • StringBuilder: Manipulation can be done with is the object itself.

Q: What is the difference between Abstract method and Virtual method ?

Ans:

Abstract Method Virtual Method
1. Must be inside abstract class 1. It can be declared any where
2. Must be overrided in its derived class  2. It may or may not be overrided in its derived class
3. Should not have the body in base class 3. Must have the body in base class

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