Sdaemon Infotech DOT NET Developer Interview Questions and Answers

Q1. What is Object Oriented Programming?
Ans. 
Object Oriented Programming is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.
• OOP focuses on creating objects that interact with each other to solve problems.

• It involves concepts like classes, objects, inheritance, polymorphism, and encapsulation.

• Example: In a banking application, you can have classes like Account, Customer, and Tr...read more
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Q2. What are the important pillars of OOPs?
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The important pillars of OOPs are Inheritance, Encapsulation, Abstraction, and Polymorphism.
• Inheritance allows a class to inherit properties and behavior from another class.

• Encapsulation hides the internal state of an object and only exposes necessary information.

• Abstraction focuses on the essential features of an object while hiding the implementation details.

• Polymorphism allows objects to be treated as instances of t...read more
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Q3. What is Encapsulation? How do you hide data using Encapsulation?
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Encapsulation is the concept of bundling data and methods that operate on the data within a single unit.
• Encapsulation helps in hiding the internal state of an object and restricting access to it.

• Data hiding is achieved by making the variables private and providing public methods to access or modify them.

• For example, a class 'Car' may have private variables like 'model' and 'year' with public methods like 'getModel()' a...read more
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Q4. What is Inheritance?
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Inheritance is a concept in object-oriented programming where a class inherits properties and behaviors from another class.
• Allows a class to inherit attributes and methods from another class

• Promotes code reusability and reduces redundancy

• Creates a parent-child relationship between classes

• Derived class can access public and protected members of the base class

• Example: Class Car inherits from class Vehicle
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Q5. What is Polymorphism?
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Polymorphism is the ability of a single function or method to operate on different data types.
• Polymorphism allows objects of different classes to be treated as objects of a common superclass.

• There are two types of polymorphism: compile-time (method overloading) and runtime (method overriding).

• Example: Inheritance allows a child class to override a method of its parent class, exhibiting polymorphic behavior.
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Q6. What is Abstract Class?
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Abstract class is a class that cannot be instantiated and may contain abstract methods.
• Cannot be instantiated directly

• May contain abstract methods that must be implemented by derived classes

• Can have both abstract and non-abstract methods
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Q7. What is difference between Abstract Class and Interface?
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Abstract class can have implementation details while interface cannot. Class can implement multiple interfaces but only inherit from one abstract class.
• Abstract class can have method implementations while interface cannot.

• A class can implement multiple interfaces but can only inherit from one abstract class.

• Interfaces are used to define a contract for classes to implement, while abstract classes are used to provide a c...read more
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Q8. What is Layout page in MVC?
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Layout page in MVC is a shared template that defines the structure of the final output HTML.
• Layout page contains common elements like header, footer, navigation menu, etc.

• It allows for consistent design across multiple views.

• Can be used to define sections that can be overridden by individual views.
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Q9. What is primary key?
Ans. 
Primary key is a unique identifier for each record in a database table.
• Primary key ensures each record in a table is unique

• It can be a single column or a combination of columns

• Primary key constraints prevent duplicate or null values
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Q10. What is Unique key?
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Unique key is a column or a set of columns that uniquely identifies each row in a table.
• A unique key constraint ensures that all values in a column or a set of columns are unique.

• It can be used to enforce data integrity and prevent duplicate entries.

• Example: Employee ID in an employee table can be a unique key.
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Q11. Can a table have multiple primary key?
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Yes, a table can have multiple primary keys.
• A table can have a composite primary key, which consists of multiple columns.

• Each column in the composite primary key contributes to uniquely identifying each row.

• Example: CREATE TABLE Employee (emp_id INT, dept_id INT, PRIMARY KEY (emp_id, dept_id));
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Q12. Query for finding ID, Name for employee with Maximum Salary
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Query to find ID and Name of employee with maximum salary
• Use SQL query with MAX() function to find the maximum salary

• Join the result with employee table to get ID and Name
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Q13. Select ID,Name from Employee where Salary = { Selelct Max(Salary) from Employee};
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The query selects the ID and Name of the employee with the highest salary.
• The query uses a subquery to find the maximum salary in the Employee table.

• The outer query then selects the ID and Name of the employee with that maximum salary.
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Q14. If you have static constructor and default constructor, which gets executed first?
Ans. 
Static constructor gets executed first before default constructor.
• Static constructor is called only once, when the class is first accessed or instantiated.

• Default constructor is called every time a new instance of the class is created.

• Example: If a class has both static and default constructors, the static constructor will be executed before the default constructor.
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Q15. Can static constructor have multiple arguments?
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No, static constructors cannot have multiple arguments.
• Static constructors in C# do not take any arguments.

• They are used to initialize static data members or perform any necessary setup for the class.

• Example: public static MyClass() { // constructor code }
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Q16. If you have class and private variable. Can you use that class in other class?
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Yes, by using access modifiers like public or internal.
• Yes, by changing the access modifier of the class to public or internal.

• Private variables can be accessed within the same class but not outside. Use properties or methods to access them in other classes.

• Example: class A has a private variable 'x'. In class B, create an instance of class A and access 'x' using a public method or property.
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