C# Interview Preparation (Questions and Answers)

1. What is .NET Framework?

.NET Framework is a software development platform developed by Microsoft used to build and run applications primarily on Windows. It provides a runtime environment and a large class library called the Framework Class Library (FCL).

2. What is .NET Core?

.NET Core is a cross-platform, open-source framework developed by Microsoft that allows developers to build applications that run on Windows, Linux, and macOS.

3. What is CLR?

CLR (Common Language Runtime) is the runtime environment of the .NET Framework that manages memory, security, exception handling, and execution of programs.

4. What is CTS?

CTS (Common Type System) defines how data types are declared, used, and managed in the runtime so that different .NET languages can share types.

5. What is CLS?

CLS (Common Language Specification) is a set of rules that languages must follow to ensure interoperability among different .NET languages.

6. What is FCL?

Framework Class Library (FCL) is a collection of reusable classes, interfaces, and value types used for developing applications.

7. What is JIT Compiler?

JIT (Just-In-Time) compiler converts Intermediate Language (IL) code into machine code at runtime.

8. What is IL Code?

Intermediate Language (IL) is a CPU-independent set of instructions produced by the .NET compiler before it is converted to machine code.

9. What is Assembly?

An Assembly is a compiled code library used by the .NET Framework consisting of metadata, IL code, and a manifest.

10. What is Metadata?

Metadata is information about a program such as classes, methods, and properties stored inside an assembly.

11. What is the difference between .NET Framework and .NET Core?

.NET Framework runs mainly on Windows, while .NET Core is cross-platform and supports Windows, Linux, and macOS.

12. What is .NET 5 / .NET 6?

.NET 5 and later versions unify .NET Framework and .NET Core into a single platform for building modern applications.

13. What is Garbage Collection?

Garbage Collection automatically manages memory by releasing unused objects from memory.

14. What is Managed Code?

Managed code is code executed by the CLR which provides services like memory management and security.

15. What is Unmanaged Code?

Unmanaged code is code that runs outside the control of the CLR, such as native C++ programs.

16. What is the Global Assembly Cache (GAC)?

GAC is a central repository used to store shared assemblies.

17. What is Strong Name Assembly?

A Strong Name Assembly is an assembly with a unique identity using a public and private key pair.

18. What is Namespace?

A Namespace is used to organize classes and avoid naming conflicts.

19. What is the difference between private and shared assembly?

Private assembly is used by a single application, while shared assembly is used by multiple applications.

20. What is the AppDomain?

AppDomain provides an isolation boundary within a process for running .NET applications.

21. What is .NET CLI?

.NET CLI is a command-line interface used for creating, building, and running .NET applications.

22. What is SDK?

SDK (Software Development Kit) contains tools, libraries, and documentation needed to develop applications.

23. What is Runtime?

Runtime is the environment where applications are executed.

24. What is NuGet?

NuGet is the package manager for .NET used to install and manage libraries.

25. What is Dependency Injection?

Dependency Injection is a design pattern used to achieve loose coupling between objects.

26. What is Middleware in .NET Core?

Middleware are software components that handle HTTP requests and responses in the pipeline.

27. What is Kestrel?

Kestrel is a cross-platform web server used in ASP.NET Core applications.

28. What is ASP.NET Core?

ASP.NET Core is a framework used for building web applications and APIs.

29. What is Web API?

Web API is used to build HTTP services that can be accessed from different clients.

30. What is MVC?

MVC stands for Model-View-Controller, an architectural pattern for web applications.

31. What is Razor?

Razor is a markup syntax used in ASP.NET for embedding server code into HTML.

32. What is Blazor?

Blazor is a framework for building interactive web UIs using C# instead of JavaScript.

33. What is Cross-Platform?

Cross-platform means software can run on multiple operating systems.

34. What is Hosting in ASP.NET Core?

Hosting refers to running applications using web servers like Kestrel or IIS.

35. What is IIS?

IIS (Internet Information Services) is a web server developed by Microsoft.

36. What is Configuration in .NET Core?

Configuration manages application settings using JSON, environment variables, or command-line arguments.

37. What is Logging?

Logging records application events, errors, and information.

38. What is Environment in .NET?

Environment defines where the application runs such as Development, Testing, or Production.

39. What is Entity Framework Core?

Entity Framework Core is an ORM used to interact with databases using .NET objects.

40. What is ORM?

ORM (Object Relational Mapping) maps database tables to objects in code.

41. What is LINQ?

LINQ allows querying collections using C# syntax.

42. What is Lambda Expression?

Lambda expressions are anonymous functions used in LINQ queries.

43. What is Async Programming?

Async programming allows tasks to run without blocking the main thread.

44. What is Task?

Task represents an asynchronous operation.

45. What is Await?

Await pauses execution until the task completes.

46. What is Thread?

A thread is the smallest unit of execution in a process.

47. What is Multithreading?

Multithreading allows multiple threads to run concurrently.

48. What is Serialization?

Serialization converts objects into a format suitable for storage or transmission.

49. What is Deserialization?

Deserialization converts serialized data back into objects.

50. What is JSON?

JSON is a lightweight data format used for data exchange.

51. What is REST API?

REST API is a web service based on HTTP methods like GET, POST, PUT, DELETE.

52. What is Microservices?

Microservices architecture divides applications into small independent services.

53. What is Docker?

Docker is used to package applications into containers.

54. What is Containerization?

Containerization packages application code and dependencies together.

55. What is API Controller?

API Controller handles HTTP requests in ASP.NET Core Web API.

56. What is Routing?

Routing maps URLs to controller actions.

57. What is Model Binding?

Model Binding automatically maps request data to parameters.

58. What is Data Annotation?

Data annotations are attributes used for validation.

59. What is Validation?

Validation ensures input data meets required rules.

60. What is Swagger?

Swagger provides API documentation and testing interface.

61. What is Middleware Pipeline?

It is a sequence of middleware components processing HTTP requests.

62. What is Startup Class?

The Startup class configures services and middleware.

63. What is Host Builder?

Host Builder sets up configuration and dependency injection.

64. What is Web Host?

Web Host manages web application startup and lifetime.

65. What is Static File Middleware?

It serves static files like images, CSS, and JavaScript.

66. What is Session?

Session stores user data temporarily on the server.

67. What is Cookie?

Cookies store small pieces of data on the client browser.

68. What is Authentication?

Authentication verifies the identity of a user.

69. What is Authorization?

Authorization determines what resources a user can access.

70. What is Identity?

ASP.NET Identity manages users, passwords, and roles.

71. What is Role-Based Security?

Security based on user roles.

72. What is Policy-Based Authorization?

Authorization using custom policies.

73. What is Dependency Container?

Container manages dependencies automatically.

74. What is Scoped Service?

Scoped services are created once per request.

75. What is Singleton Service?

Singleton services are created once per application.

76. What is Transient Service?

Transient services are created every time requested.

77. What is Health Check?

Health checks monitor application status.

78. What is gRPC?

gRPC is a high-performance RPC framework.

79. What is SignalR?

SignalR enables real-time communication.

80. What is Caching?

Caching stores frequently accessed data.

81. What is Distributed Cache?

Cache shared across multiple servers.

82. What is Memory Cache?

Cache stored in server memory.

83. What is Rate Limiting?

Limits number of requests from clients.

84. What is Health Endpoint?

Endpoint used to check system health.

85. What is Background Service?

Service running tasks in background.

86. What is Worker Service?

A background service template in .NET.

87. What is Configuration Provider?

Provides configuration data from different sources.

88. What is Options Pattern?

Used to bind configuration settings to classes.

89. What is Minimal API?

Minimal API is a lightweight way to build APIs in .NET.

90. What is Endpoint Routing?

Routing system used in ASP.NET Core.

91. What is Hosting Model?

Defines how an application runs on server.

92. What is Self-Hosting?

Running web applications without IIS.

93. What is Reverse Proxy?

A server that forwards client requests to backend servers.

94. What is WebSockets?

Protocol enabling full-duplex communication.

95. What is Cloud Deployment?

Deploying applications to cloud platforms.

96. What is Azure?

Microsoft Azure is a cloud computing platform.

97. What is CI/CD?

Continuous Integration and Continuous Deployment automate builds and releases.

98. What is Versioning?

Managing different API versions.

99. What is Monitoring?

Monitoring tracks performance and errors.

100. What is Application Lifecycle?

It includes development, deployment, maintenance, and updates of software.