Top 50 Most Asked C# Programs for Freshers to Experienced Candidates


These programs are commonly asked in C# interviews for:

  • Freshers

  • Junior Developers

  • Mid-Level Developers

  • Experienced .NET Developers

They cover:

  • Basics

  • OOP

  • Arrays & Strings

  • Collections

  • LINQ

  • File Handling

  • Exception Handling

  • Multithreading

  • Advanced C#


Basic C# Programs

1. Hello World Program

Console.WriteLine("Hello World");

2. Swap Two Numbers

3. Find Even or Odd Number

4. Find Largest of Three Numbers

5. Check Leap Year

6. Reverse a Number

7. Palindrome Number

8. Armstrong Number

9. Prime Number Check

10. Fibonacci Series


String Programs

11. Reverse a String

string str = "hello";
char[] arr = str.ToCharArray();
Array.Reverse(arr);
Console.WriteLine(new string(arr));

12. Check Palindrome String

13. Count Vowels and Consonants

14. Find Duplicate Characters in String

15. Remove Duplicate Characters

16. Count Words in String

17. Find First Non-Repeated Character

18. Check Anagram Strings

19. String Compression Program

20. Find Frequency of Characters


Array Programs

21. Find Largest Element in Array

22. Find Second Largest Number

23. Sort Array in Ascending Order

24. Bubble Sort Program

25. Binary Search Program

26. Linear Search Program

27. Remove Duplicates from Array

28. Merge Two Arrays

29. Find Missing Number in Array

30. Rotate Array


OOPs Programs

31. Class and Object Example

class Student
{
    public string Name;

    public void Display()
    {
        Console.WriteLine(Name);
    }
}

32. Inheritance Example

33. Polymorphism Example

34. Method Overloading

35. Method Overriding

36. Encapsulation Example

37. Abstraction Example

38. Interface Example

39. Constructor and Destructor

40. Singleton Design Pattern


Collections & LINQ Programs

41. List Example

List<int> numbers = new List<int>() {1,2,3};

42. Dictionary Example

43. Stack Implementation

44. Queue Implementation

45. Find Duplicate Elements Using LINQ

var duplicates = numbers.GroupBy(x => x)
                        .Where(g => g.Count() > 1)
                        .Select(y => y.Key);

46. Sort List Using LINQ

47. Filter Data Using LINQ

48. Lambda Expression Example

49. Delegate and Event Program

50. Async Await Example

public async Task GetData()
{
    await Task.Delay(1000);
    Console.WriteLine("Completed");
}

Most Asked Advanced C# Interview Programs

These are highly important for experienced candidates:

  • CRUD Operations using ADO.NET

  • Entity Framework CRUD

  • Dependency Injection

  • Repository Pattern

  • Unit of Work Pattern

  • Multithreading

  • Deadlock Example

  • Producer Consumer Problem

  • File Upload Program

  • API Calling using HttpClient

  • JWT Authentication

  • Reflection Example

  • Serialization & Deserialization

  • Generic Class Example

  • Extension Methods

  • Middleware Example in ASP.NET Core


Most Important Topics for Freshers

Focus on these first:

  1. Strings

  2. Arrays

  3. OOP Concepts

  4. Collections

  5. Exception Handling

  6. Delegates

  7. LINQ

  8. Async/Await

  9. File Handling

  10. SQL + C# Integration


Common Interview Follow-Up Questions

Interviewers may ask:

  • Time Complexity

  • Difference between Array and List

  • IEnumerable vs IQueryable

  • Abstract Class vs Interface

  • Ref vs Out vs In

  • String vs StringBuilder

  • Task vs Thread

  • Async vs Parallel

  • Boxing vs Unboxing

  • Dispose vs Finalize


Recommended Preparation Roadmap

Beginner

  • Basic Programs

  • Loops

  • Arrays

  • Strings

Intermediate

  • OOP

  • Collections

  • Exception Handling

  • LINQ

Advanced

  • ASP.NET Core

  • Entity Framework

  • Multithreading

  • Design Patterns

  • Web APIs

  • Authentication



This was part of Interview Preparation With Bipin — Let’s Crack It!

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