C# Interview Questions and Answers

It is type-safe and a managed language. Many operating systems use it, so one must understand this language strongly. It is highly in demand, and due to its versatility, it can support many operating systems.

You have finally found your dream job in C# but are wondering how to crack the 2023 C# Interview and what the probable C# Interview Questions could be. Every interview is different, and the job scopei is different too. Keeping this in mind, we have designed the most common C# Interview Questions and Answers to help you get success in your interview.

Part 1 – C# Interview Questions (Basic)

This first part covers basic C# Interview Questions and answers.

Q1. What is Managed and Unmanaged code?

Answer:

Managed code is executed on the .Net platform. It uses CLR (Common Language Runtime) for all application code based on that platform. The application, when executed, is responsible for managing factors such as memory, security, and performance. These are among the key C# interview questions that one might expect in an interview.

Q2. What are the different types of classes in C#? Explain each class in short.

Answer:

There are four types of classes in C#. They are as follows:

1) Static class: This class does not allow inheritance. The members within this class are static and identified by the keyword “static”.

2) Abstract class: This class is denoted by the keyword abstract. The objects of these classes cannot be instantiated. This class can only be inherited and must contain at least one method.

3) Sealed class: This class cannot be inherited. To access, an object of this class should be created. It is made using the keyword Sealed.

4) Partial class: By using the “partial” keyword, a class can be designated as “partial,” which permits its members to be divided or shared among multiple .cs files.

Let’s move on to the following C# Interview Questions.

Q3. What are C# I/O classes?

Answer:

C# uses the System.IO namespace, which consists of classes that perform various operations like create, delete, open, close, etc. The commonly used I/O classes are:

• File: Helps in performing multiple operations on a file. It helps in the creation and manipulation of files.
• StreamWriter: For writing characters to a stream.
• StreamReader: Used for reading characters from a stream.
• StringWriter: Used for writing a string to a buffer.
• StringReader: Used for reading a line from a pad.
• Path: Used when a user wants to perform operations related to the course.

Q4. Explain StreamReader/ StreamWriter class.

Answer:

Both these classes belong to namespace System.IO. StreamReader class includes members like: close(), read(), Readline(). StreamWrier class includes members like close(), write(), writeline().

class Program1
{
using(StreamReader sr = new StreamReader("C:\ReadMe.txt")
{
//----------------code to read-------------------//
}
using(StreamWriter sw = new StreamWriter("C:\ReadMe.txt"))
{
//-------------code to write-------------------//
}
}

Q5. Explain the concept of Boxing and Unboxing?

Answer:

Boxing is a value is converted to a reference type.

Example:

int value -= 20;
//-----------Boxing------------//
Object boxValue= value;

Here boxValue references ‘value’.
Unboxing is the process of explicitly converting from a reference type back to a value type.

Example:

//————UnBoxing——————//
int UnBoxing = int (boxedValue);

Unboxing references back to original value.

Part 2 – C# Interview Questions (Advanced)

Let us now have a look at the advanced C# Interview Questions.

Q6. What are Regular Expressions? Write a regex to find a string using?

Answer:

Regular expressions patterns to templates to match a given set of input. These patterns may contain operators, character literals, symbols, etc. Developers commonly use regular expressions (regex) to parse strings or replace specific characters within them. Using regex, developers can search for any pattern in a given input file or string, making it a powerful tool for processing text-based data.
Example:

static void Main(string[] args)
{
string[] lang = { "C#", "Python", "Java" };
foreach(string s in lang)
{
if(System.Text.RegularExpressions.Regex.IsMatch(s,"Python"))
{
Console.WriteLine("Match found");
}
}
}

This code example utilizes Python to search for a specific language within an array. This method allows developers to use regular expressions to locate specific matches within the input.

Q7. What are the different types of Delegates?

Answer:

The different types of delegates are:

• Single Delegate: When a delegate calls a single method, it is a single delegate.
• • Multicast Delegate: When a delegate calls multiple methods, it is a multicast delegate. A user can use the + and – operators to subscribe and unsubscribe.
  • Generic Delegate: Generic delegates are of three types. They are Actions, Funcs, and Predicates.

Q8.  What is a lambda expression in C#?

Answer: A lambda expression is a concise way to define anonymous methods in C#. It is often used in LINQ queries and for defining delegates or event handlers. Lambda expressions make the code more readable and expressive.

Q9. What are delegates in C#?

Answer: A delegate is a type that represents references to methods with a particular parameter list and return type. Delegates are used for defining callback methods and implementing event handling and are a fundamental part of C# events and callbacks.

Q10. Explain the concept of boxing and unboxing in C#.

Answer: Boxing is the process of converting a value type to a reference type, and unboxing is the reverse process of converting a boxed value back to a value type. Boxing and unboxing can have a performance impact, so they should be used judiciously.

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