100 Frequently asked C# interview questions

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C# encompasses two primary categories of data types: value types and reference types. Value types consist of primitive types such as int, float, double, and bool, as well as user-defined structs. Reference types include objects, strings, and user-defined classes.

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C# supports three loop types: for, while, and do-while. The for loop is employed for iterating over a sequence of values. The while loop executes a block of code repeatedly as long as a specific condition remains true. The do-while loop is similar to the while loop but ensures that the loop body is executed at least once.

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In C#, exception handling is accomplished using try-catch-finally blocks. The code that may throw an exception is placed within the try block.

• The catch block is utilized to catch and handle the exception.
• The finally block is applied to execute code that should be run irrespective of whether an exception was thrown.

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Object-oriented programming (OOP) is a programming paradigm that employs objects and classes to organize code. C# is an object-oriented language that supports OOP concepts such as encapsulation, inheritance, and polymorphism.

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Inheritance is a fundamental feature of object-oriented programming that enables a subclass to inherit properties and methods from its superclass. Inheritance in C# is achieved using the “extends” keyword. The subclass has the ability override methods of the superclass and introduce new methods and properties.

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Polymorphism is another essential concept in OOP that allows objects of different classes to be treated as if they belong to the same type. Polymorphism in C# is achieved through two mechanisms: inheritance and interfaces. Polymorphism facilitates code reuse and simplifies the maintenance of large codebases.

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Encapsulation is the practice of concealing the internal implementation details of an object from the external world. In C#, encapsulation is attained using access modifiers such as public, private, and protected. Encapsulation ensures that the internal state of an object cannot be unintentionally modified from outside the class.

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Abstraction is the process of hiding implementation details while only showing the necessary information to the user.
In C#, abstraction can be achieved through abstract classes, interfaces, and access modifiers.

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A delegate in C# is a type that characterizes a reference to a method with a specific signature. Delegates enable passing methods as parameters, making them useful for implementing callback methods.

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A lambda expression in C# is a concise way to define an anonymous method. It allows the creation of functions without explicitly defining a separate method and is commonly used in LINQ queries.

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• C# offers an accessible learning curve, making it easier for beginners to learn.
• C# is a versatile, object-oriented programming language.
• C# facilitates component-oriented development
• C# is a structured language, supporting readability of code.
• C# can be compiled on multiple platforms.
• Programs written in C# tend to be efficient.
• C# is an integral part of the .NET Framework.

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A thread in C# refers to an independent execution path within a program that operates concurrently alongside the main program flow. Threads enable multitasking and parallel processing, thereby enhancing program performance by executing tasks simultaneously.

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Below are the points of differences between throw and throw ex:

• Syntax
  • Throw
  • Throw ex
• Behavior
  • Throw throws the exception and preserves the original stack trace
  • Throw ex throws the exception and replaces the original stack trace with the current one
• Use case
  • Throw is utilized to propagate an exception that has been caught
  • Throw ex is utilized to propagate an exception that has been caught, but with a modified stack trace.

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An interface in C# defines a contract that specifies a set of methods, properties, and events that must be implemented by a class. It facilitates abstraction and loose coupling, promoting modularity and flexibility in code design.

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In C#, a struct is a value type, whereas a class is a reference type. Structs are stored on the stack, while classes are stored on the heap. Structs are commonly used for lightweight objects, whereas classes are suitable for more complex objects.

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In C#, a namespace is a mechanism for organizing code. It provides a way to keep one set of names distinct from another. Namespaces help prevent naming conflicts and are used to organize classes in the .NET framework. Declaring custom namespaces aids in controlling the scope of names in larger projects.

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A constructor is a special method useful for initializing objects in C#. A constructor in C# is invoked automatically when an object is created, and it can receive parameters to set the initial values of the object’s properties.

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A static constructor in C# is a special type of constructor that initializes static data members of a class. It is called only once, before the first instance of the class is created or any static members are accessed. It cannot take parameters, must have a private access modifier. The aim of a static constructor is to guarantee static members are initialized before use.

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In C#, a sealed class is one that cannot be inherited from. It is marked with the ‘sealed’ keyword and prevents further derivation in the class hierarchy. Sealed classes are often used to protect the implementation details of a class from modification or extension.

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A generic class in C# is a class that can operate on multiple data types without the need for separate implementations. It is defined using type parameters, which are specified when the class is instantiated. Generic classes have generic methods and properties and are valuable for creating reusable data structures and algorithms.