C# is a popular programming language that is widely used for developing applications on the Microsoft platform. It is an object-oriented language that supports various OOP concepts such as classes, objects, encapsulation, inheritance, polymorphism, and more. As a result, many companies use C# as their primary programming language, and as a result, the demand for C# developers has increased.
If you are preparing for a C# developer interview, it’s important to have a solid understanding of C# and OOP concepts. In this article, we will provide you with the top interview questions for C# and OOP, along with examples and explanations.
What is C#?
C# is a modern, object-oriented programming language that is used to develop Windows applications, web applications, games, and more.
What is the difference between an abstract class and an interface in C#?
An abstract class can contain both abstract and non-abstract methods, while an interface can only contain abstract methods.
What is a lambda expression in C#?
A lambda expression is an anonymous function that can be used to create delegates or expression trees.
What is the difference between var and dynamic in C#?
The var keyword is used to declare a variable with an implicit type, while the dynamic keyword is used to declare a variable with a dynamic type.
What is a partial class in C#?
A partial class is a class that can be split across multiple files.
What is the difference between an object and a class in C#?
A class is a blueprint for an object, while an object is an instance of a class.
What is the difference between a private and a protected member in C#?
A private member can only be accessed within the same class, while a protected member can be accessed within the same class or any derived classes.
What is the difference between an event and a delegate in C#?
An event is a delegate with additional access control and event handlers.
What is the difference between an abstract class and a sealed class in C#?
An abstract class cannot be instantiated, while a sealed class cannot be inherited.
What is the difference between a static class and a non-static class in C#?
A static class can only contain static members, while a non-static class can contain both static and non-static members.
What is the difference between a foreach loop and a for loop in C#?
A foreach loop is used to iterate over a collection, while a for loop is used to iterate over a range of values.
What is the difference between a throw and a throw ex in C#?
A throw statement re-throws the exception, while a throw ex statement replaces the original exception with a new one.
What is the difference between a value type and a reference type in C#?
- A value type is stored on the stack, while a reference type is stored on the heap.
- A value type stores its value directly in memory, while a reference type stores a reference to its value in memory.
What is a property in C#?
A property is a member of a class that provides access to a private field.
What is the difference between a get and a set accessor in C#?
A get accessor is used to retrieve the value of a property, while a set accessor is used to set the value of a property.
What is the difference between a sealed class and a static class in C#?
A sealed class cannot be inherited, while a static class cannot be instantiated.
What is an extension method in C#?
An extension method is a static method that extends the functionality of an existing type.
How do you define an extension method in C#?
To define an extension method, you must create a static class and a static method within that class. The first parameter of the method must be the type being extended, and the parameter must be preceded by the ‘this’ keyword.
What is a using directive?
A using directive is used to import namespaces into a C# program. It allows developers to use classes and methods without having to fully qualify them with their namespace.
What is object-oriented programming?
Object-oriented programming (OOP) is a programming paradigm that uses objects to represent real-world entities. OOP allows developers to organize code in a modular and reusable way.
What is a class?
A class is a blueprint for creating objects. It defines the properties and behavior of an object.
What is an object?
An object is an instance of a class. It has its own unique set of properties and behavior.
What is a constructor?
A constructor is a special method that is used to create an object. It initializes the properties of the object when it is created.
What is an interface?
An interface is a contract between a class and the code that uses it. It defines a set of methods and properties that a class must implement.
What is inheritance?
Inheritance is a mechanism in which one class inherits the properties and behavior of another class. It allows developers to reuse code and create hierarchies of classes.
What is polymorphism?
Polymorphism is the ability of an object to take on multiple forms. It allows developers to write code that can work with objects of different types.
What is encapsulation?
Encapsulation is the process of hiding the internal details of an object from the outside world. It is achieved by making the properties and methods of an object private and exposing only the necessary information through public methods.
What is abstraction?
Abstraction is the process of simplifying complex systems by breaking them down into smaller, more manageable parts. In C#, abstraction is achieved through the use of abstract classes and interfaces.
What is a delegate?
A delegate is a type that represents a method signature. It allows developers to pass methods as arguments to other methods.
What is an event?
An event is a mechanism in C# that allows objects to communicate with each other. It allows one object to notify other objects when something happens.
What is a namespace?
A namespace is a way of organizing code into logical groups. It helps to avoid naming conflicts and makes code easier to understand and maintain.
What is a static class?
A static class is a class that can only contain static members. It cannot be instantiated, and its members can be accessed without creating an instance of the class.
What is a sealed class?
A sealed class is a class that cannot be inherited. It is used to prevent other developers from extending the functionality of the class.
What is a partial class?
A partial class is a class that is split across multiple files. It allows developers to separate the implementation of a class into smaller, more manageable parts.
What is a generic class?
A generic class is a class that is defined with one or more type parameters. It allows developers to create classes that can work with any data type.
What is a generic method?
A generic method is a method that is defined with one or more type parameters. It allows developers to write methods that can work with any data type.
What is the difference between a struct and a class in C#?
A struct is a value type, while a class is a reference type. Structs are stored on the stack, while classes are stored on the heap.
What is boxing and unboxing in C#?
Boxing is the process of converting a value type to an object type, while unboxing is the process of converting an object type to a value type.
What is the difference between an abstract class and an interface in C#?
An abstract class can contain both abstract and non-abstract members, while an interface can only contain abstract members. An abstract class can provide a default implementation for its members, while an interface cannot.
What is a virtual method in C#?
A virtual method is a method that can be overridden by a derived class. It allows developers to provide a default implementation for a method, while allowing derived classes to customize the behavior.
What is an abstract method in C#?
An abstract method is a method that is declared without an implementation. It must be implemented by any class that inherits from the abstract class.
What is a static constructor in C#?
A static constructor is a special method that is called once when a class is first loaded into memory. It is used to initialize static members of the class.
What is a nested class in C#?
A nested class is a class that is defined inside another class. It is used to group related functionality and to hide implementation details.
What is a thread in C#?
A thread is a separate path of execution within a program. It allows developers to write concurrent code that can execute simultaneously.
What is a mutex in C#?
A mutex is a synchronization object that is used to coordinate access to a shared resource. It allows multiple threads to access the resource in a coordinated way.
What is a semaphore in C#?
A semaphore is a synchronization object that is used to control access to a shared resource. It allows multiple threads to access the resource at the same time, but limits the number of threads that can access it simultaneously.
What is the difference between a task and a thread in C#?
A task is a high-level abstraction that represents an asynchronous operation. It can be executed on a separate thread, or it can be executed on the same thread as the caller. A thread is a lower-level abstraction that represents a separate path of execution within a program.
