Top 20 C# interview questions and answers for 2023

C# interview questions and answers are one of the most searched questions regarding programming, and this article attempts to provide assistance with C# interview questions and answers for beginners and advanced-level C# programmers.

C# is a modern high-level programming object-oriented language developed by Microsoft in the early 2000s, designed for general purposes and with a syntax similar to C and C++. C# is used in different applications like desktop applications, and game and website development, used in conjunction with Microsoft. NET framework, which has a set of distinctive libraries for robust applications. C# has many popular features like:

• C# is a typed-programming language where all variables must be declared within a specific type, improving the reliability of coding.
• C# uses automatic memory management freeing up memory that is no longer required and is less prone to memory leaks.
• C# has a robust system to handle errors
• C# can easily integrate with other languages that run on the .NET framework.

Here are 10 C sharp interview questions and answers for beginners and the top 10 C# interview questions and answers for experienced professionals.

How to learn C#

Basic knowledge of working with command-line, and installing applications like compilers and interpreters as well as file systems are required. Since C# is an object-oriented programming language, basic knowledge of C, C#, Python or Java can help you understand the syntax better.
In this language, you have access to a huge amount of libraries, and a strong set of abstractions. You need to learn how to understand the syntax of the language and declare variables. After this, learn about branching and looping statements that create programs for repetitive tasks. Learn about functions and methods allowing code to be grouped together for performing specific functions, and then learn about arrays, classes and objects, interfaces and inheritance, to define different methods of subclasses.

Here are the top 10 C# basics for interview questions and answers:

1. What is the difference between static, public and void?
   • Static declares a variable that belongs to the class rather than the need to create an instance in the class, creating one variable for all instances, often used for utility functions.
   • Public specifies that a class member can be accessed from any part of the program, any code that has a reference to the marking code.
   • Void is a type modifier stating the method doesn’t return a value. So with the ‘void’ method as the return type, it will not provide any value.
2. Define constructors.
   A constructor is a special method that is used to initialize the state of an object when it is created. It has the same name as the class and does not have a return type.
3. What are jagged arrays?
   A multidimensional array with each row with a different number of columns, and also not a fixed number of rows. With each element treated as an array, it has a different number of elements.
4. What is serialization?
   Serialisation is the process of converting the format of an object and data structure which can be stored and altered later. Objects and data structures can be converted into a stream of bytes, saved into files, transmitted into the network and shared between applications and programming languages.
5. Explain the four steps with C# code compilation.
   The four steps with C# code compilation are:
   • Sourced code compilation in managed code.
   • Clubbing together newly created code and assembled code
   • Loading Common Language Runtime
   • Executing assembly code through runtime.
6. Name all the C# access modifiers.
   The four C# access modifiers are:
   • Private access modifier: a private method that can be accessed from inside the class.
   • Public access modifier: publicly declaring a method so that it can be accessed from anywhere in the class.
   • Internal access modifier: a method is declared as internal, to be accessed by the current assembly point of the class.
   • Protected access modifier: once a method is declared protected, it can be accessed by members of a class, and those who are part of the class.
7. What are the features of C# programming language?
   C# has many popular features like:
   • C# is a typed-programming language where all variables must be declared within a specific type, improving the reliability of coding.
   • C# uses automatic memory management freeing up memory no longer required and is less prone to memory leaks.
   • C# has a robust system to handle errors
   • C# can easily integrate with other languages that run on the .NET framework.
8. What is meant by unmanaged or managed code?
   When a code is executed by the Common Language Runtime (CLR), and the application code is dependent on its .NET platform, and therefore is considered as overseen, it is called managed code. When code executed by the CLR isn’t dependent on the.NET platform, it is unmanaged code.
9. What is meant by an interface class?
   An interface class is an object-oriented programming blueprint specifying a set of methods and properties that has to be implemented by the class, in order to be compatible with the interface.
10. What are circular references?
    When resources become dependent on each other, they refer to each other to form a loop. This creates a lock condition, and objects and modules are collected like garbage, and the resources are becoming unusable.

Here are the top 10 C# interview questions and answers for experienced professionals:

1. What is the difference between a value type and a reference type in C#?
   Value types store the actual data in memory, while reference types store a reference to the data in memory. Examples of value types include int, float, and bool, while examples of reference types include classes, arrays, and strings.
2. What is the purpose of the using statement in C#?
   The using statement is used to automatically dispose of objects that implement the IDisposable interface, such as streams or database connections after they are no longer needed. This helps ensure that resources are properly managed and released.
3. What is the difference between abstract classes and interfaces in C#?
   Abstract classes can contain both abstract and non-abstract methods, while interfaces can only contain method signatures. A class can inherit from multiple interfaces, but can only inherit from one abstract class.
4. What is LINQ and how is it used in C#?
   LINQ stands for Language-Integrated Query and is used to query collections of objects in C#. It provides a consistent syntax for querying data from different sources, such as arrays, lists, and databases.
5. What is a delegate in C#?
   A delegate is a type that represents a reference to a method. It can be used to encapsulate a method call and pass it around as an object. Delegates are commonly used in event-driven programming.
6. What is the difference between a private and a protected method in C#?
   A private method can only be accessed within the same class, while a protected method can be accessed within the same class and any derived classes.
7. What is the purpose of the static keyword in C#?
   The static keyword is used to define members that belong to the type itself, rather than to a specific instance of the type. Static members can be accessed without creating an instance of the type.
8. What is an extension method in C#?
   An extension method is a static method that is used to extend the functionality of an existing type. It is called as if it were an instance method of the type it extends but is defined in a separate class.
9. What is the difference between a value parameter and a reference parameter in C#?
   A value parameter passes a copy of the parameter's value to the method, while a reference parameter passes a reference to the parameter's value. Changes made to a reference parameter inside the method are reflected in the original variable outside the method.
10. What is the difference between method overriding and method overloading?
    These are two concepts in object-oriented programming creating multiple methods. Method overriding is multiple methods having the same name with different parameters or different signatures, to have more flexibility and increase code readability for calling methods.
    Method overloading specifies how a method has to be implemented and as the method definition changes in the derived class, this laters the change in method.