What is the main difference between a record and a class in C#?

Classes are primarily designed for mutable objects and use reference equality by default, whereas records are designed for immutable data models and provide value-based equality by default.

What problem arises from combining read and write logic in the same service in an application, and what design pattern can help refactor it?

Combining read and write logic in one service makes it complex, hard to maintain, and violates the single responsibility principle. The CQRS (Command Query Responsibility Segregation) pattern helps by separating reads and writes into different services for better clarity and scalability.

Name at least 3 thread-safe data structures in .NET you would use in a multi-threaded environment.

Here are three thread-safe data structures in .NET for multi-threaded environments:

ConcurrentDictionary<TKey, TValue>
ConcurrentQueue<T>
ConcurrentBag<T>

What is the key difference between OIDC and SAML?

OIDC is more lightweight and API-friendly (JSON/REST), while SAML is heavier and XML-based, commonly used in traditional enterprise SSO setups.

What will be printed to the console and why?

The console is a simple way to communicate with the user during program execution 

 Console.WriteLine() to print messages or data to the console window. So, the users can see program output or debug information.
 Console.ReadLine() to take input from the user