💡 C# (C Sharp) – Interview-Focused Topics

This section covers essential C# programming concepts that are commonly asked in technical interviews. Learn object-oriented programming, interfaces, abstraction, inheritance, generics, delegates, async/await, LINQ, and more — all with code samples, MCQs, and real interview questions.

• 1. What is C#?
• 2. Main Features of C#
• 3. Difference Between C# and Java
• 4. Common Language Runtime (CLR) in C#
• 5. Common Type System (CTS) in C#
• 6. Common Language Specification (CLS) in C#
• 7. Value Types vs Reference Types in C#
• 8. What is a Namespace in C#?
• 9. Purpose of the 'using' Keyword in C#
• 10. Different Data Types in C#
• 11. Difference Between int and Int32 in C#
• 12. Difference Between float, double, and decimal in C#
• 13. What is the Default Value of a Boolean in C#?
• 14. What is Boxing and Unboxing in C#
• 15. What are the Different Types of Operators in C#
• 16. Difference Between
• 17. What is the Null-Coalescing Operator ?? in C#
• 18. What is the Ternary Operator in C#
• 19. How Does the Switch Statement Work in C#
• 20. What is Object-Oriented Programming in C#
• 21. What are the Four Pillars of OOP in C#
• 22. What is Encapsulation in C#
• 23. What is Inheritance in C#
• 24. What is Polymorphism in C#
• 25. What is Abstraction in C#
• 26. What is an Abstract Class in C#
• 27. What is an Interface in C#
• 28. Can a Class Implement Multiple Interfaces in C#?
• 29. Difference Between Abstract Class and Interface in C#
• 30. How Do You Create a Class in C#?
• 31. What is a Constructor in C#
• 32. What Are the Types of Constructors in C#
• 33. What is a Static Constructor in C#
• 34. Difference Between Static and Non-Static Members in C#
• 35. What is the Use of 'this' Keyword in C#
• 36. What is a Destructor in C#
• 37. What is Object Initializer Syntax in C#
• 38. What is the Difference Between Field and Property in C#
• 39. What are Auto-Implemented Properties in C#
• 40. What is a Read-Only Property in C#
• 41. What are Indexers in C#
• 42. What are Access Modifiers in C#
• 43. What are Static Methods in C#
• 44. What is Method Overloading in C#
• 45. What is Method Overriding in C#
• 46. What is a Struct in C#
• 47. What is the Difference Between Class and Struct in C#
• 48. What is an Enum in C#
• 49. What is a Record Type in C#
• 50. What is a Delegate in C#
• 51. What are Multicast Delegates in C#
• 52. What are Anonymous Methods in C#
• 53. What is an Event in C#
• 54. Difference Between Delegate and Event in C#
• 55. What is a Lambda Expression in C#
• 56. What is LINQ in C#
• 57. What are Deferred and Immediate Execution in LINQ?
• 58. What is the difference between Select and SelectMany?
• 59. What is the difference between Array and ArrayList?
• 60. What is a List in C#
• 61. What is a Dictionary?
• 62. What are Generics in C#
• 63. What is the difference between IEnumerable and IEnumerator?
• 64. What is the difference between IEnumerable and IQueryable?
• 65. What is Exception Handling in C#
• 66. What are try, catch, finally blocks?
• 67. What is mocking?
• 68. What is test coverage?
• 69. What is serialization?
• 70. What is the difference between binary and XML serialization?
• 71. What is JSON serialization?
• 72. How do you call unmanaged code in C#
• 73. What is P/Invoke?
• 74. What are best practices for exception handling?
• 75. What is exception handling in C#
• 76. What is the difference between throw and throw ex?
• 77. What is a custom exception?
• 78. What is the base class for all exceptions in C#
• 79. What is garbage collection in C#
• 80. What is the purpose of IDisposable?
• 81. What is a memory leak?
• 82. What is finalizer in C#
• 83. What are strong and weak references?
• 84. What is multithreading in C#
• 85. What is the Thread class?
• 86. What is the Task Parallel Library?
• 87. What is async and await?
• 88. What is the difference between Task and Thread?
• 89. What is a deadlock?
• 90. What is thread safety?
• 91. How do you read and write files in C#
• 92. What are streams in C#
• 93. What is a List in C#
• 94. What is a Dictionary?
• 95. What is exception handling in C#
• 96. how-to-handle-large-object-memory
• 97. defensive-programming
• 98. how-to-write-clean-maintainable-csharp-code
• 99. reverse-string-without-built-in
• 100. find-first-non-repeating-character
• 101. implement-singleton-class
• 102. detect-loop-in-linked-list
• 103. thread-safe-singleton
• 104. convert-string-to-int-without-parse
• 105. generate-fibonacci-using-recursion-and-loop
• 106. what-is-nameof-operator
• 107. what-is-null-conditional-operator
• 108. what-are-tuples-in-csharp
• 109. what-is-span
• 110. what-is-yield-keyword
• 111. what-is-difference-between-const-and-readonly
• 112. how-to-handle-circular-references-in-serialization
• 113. what-is-difference-between-ref-and-out
• 114. what-is-dependency-injection-in-net-core
• 115. what-are-solid-principles
• 116. what-is-model-binding
• 117. how-does-dependency-injection-work-in-aspnet-core
• 118. how-do-you-use-logging-in-aspnet-core
• 119. what-are-middleware-and-how-do-you-create-custom-middleware
• 120. ioptions-pattern-configuration
• 121. what-is-unit-testing
• 122. what-is-mocking
• 123. what-is-test-coverage
• 124. how-do-you-call-unmanaged-code-in-csharp
• 125. what-is-pinvoke
• 126. what-are-best-practices-for-exception-handling
• 127. how-to-handle-large-object-memory
• 128. what-is-defensive-programming
• 129. how-to-write-clean-maintainable-code
• 130. reverse-a-string-without-using-built-in-functions
• 131. detect-a-loop-in-a-linked-list
• 132. write-thread-safe-singleton
• 133. convert-string-to-int-without-int-parse
• 134. what-is-dependency-injection-in-dotnet-core
• 135. what-are-nullable-reference-types