24 questions that come up in C# technical interviews, each with the answer and an explanation of why it is right.
Test yourself — 90 question bankAnswer: Examines and manipulates types at runtime
Reflection examines and manipulates types, methods, properties at runtime. Use System.Reflection namespace. Enables dynamic invocation, attribute reading. Performance cost.
Answer: Language Integrated Query for querying collections
LINQ (Language Integrated Query) provides query capabilities for collections. Supports query syntax and method syntax. Works with IEnumerable and IQueryable.
Answer: Modern, object-oriented programming language by Microsoft
C# is a modern, object-oriented, type-safe programming language developed by Microsoft. It runs on .NET platform and is used for various applications.
Answer: Automatic memory management system
Garbage Collector (GC) automatically manages memory. Reclaims unused objects. Runs in generations (0, 1, 2). Can be tuned but generally leave to runtime.
Answer: IEnumerable in-memory, IQueryable for databases
IEnumerable executes queries in-memory (LINQ to Objects). IQueryable translates to database queries (LINQ to SQL/EF). IQueryable supports deferred execution with expression trees.
Answer: Type-safe function pointer
Delegate is type-safe function pointer. References methods with matching signature. Enables callbacks, events, method passing. Foundation for events and lambdas.
Answer: Gen 0 (young), Gen 1 (medium), Gen 2 (old)
GC uses three generations: Gen 0 (newly allocated, collected frequently), Gen 1 (survived one collection), Gen 2 (long-lived objects). Optimizes collection.
Answer: No difference, int is alias for Int32
int is a C# keyword that is an alias for System.Int32. They are completely interchangeable. int is preferred for readability.
Answer: Notification mechanism using delegates
Events provide notification mechanism using delegates. Publishers raise events, subscribers handle them. Uses += to subscribe, -= to unsubscribe. Based on observer pattern.
Answer: Interface for releasing unmanaged resources
IDisposable interface provides mechanism for releasing unmanaged resources (file handles, database connections). Implement Dispose() method. Use with using statement.
Answer: Pattern for deterministic resource cleanup
Dispose pattern implements IDisposable with protected virtual Dispose(bool) method. Handles both managed and unmanaged resources. Prevents finalization if disposed.
Answer: Anonymous function with concise syntax
Lambda expression is anonymous function using => operator. Example: x => x * 2. Used with LINQ, delegates, expression trees. More concise than anonymous methods.
Answer: Asynchronous programming pattern
async/await enables asynchronous programming. async methods return Task, await suspends execution without blocking thread. Improves responsiveness and scalability.
Answer: == compares references, Equals() compares values
For reference types, == typically compares references (same object), Equals() compares values (content). Can be overridden for custom behavior.
Answer: Cleanup before garbage collection via finalizer
Finalization runs cleanup code before GC reclaims memory. Use ~ClassName() syntax. Non-deterministic timing. Avoid unless necessary for unmanaged resources.
Answer: Reference not preventing garbage collection
Weak reference allows referencing objects without preventing garbage collection. Use WeakReference class. Useful for caches, large object graphs.
Answer: Blueprint for creating objects
A class is a blueprint/template for creating objects. It defines properties, methods, and events. Core concept of object-oriented programming.
Answer: Represents asynchronous operation
Task represents asynchronous operation. Can return value (Task<T>) or no value (Task). Use Task.Run() for CPU-bound work, async methods for I/O-bound.
Answer: Type with type parameters enabling type safety and reuse
Generic types use type parameters for type safety and code reuse. Example: List<T>. Compiler generates type-specific code. Avoid boxing, runtime type checking.
Answer: Instance of a class
An object is an instance of a class. Created using new keyword. Contains actual data and can call methods defined in the class.
Answer: Type-safe, stack-allocated memory view
Span<T> is type-safe, stack-allocated view over contiguous memory. Zero-copy operations. High performance. Cannot be stored on heap. Use for performance-critical code.
Answer: Heap-allocatable memory view like Span
Memory<T> is heap-allocatable alternative to Span<T>. Can be stored in fields, async methods. Represents contiguous region of memory. Use with async operations.
Answer: Mechanism where class inherits members from base class
Inheritance allows a class to inherit members (fields, properties, methods) from a base class. Promotes code reuse. Use : syntax.
Answer: Data structure storing multiple items
Collections store multiple items. Common: List<T>, Dictionary<K,V>, HashSet<T>, Queue<T>, Stack<T>. More flexible than arrays. Support generics.
The full C# bank has 90 questions across 3 difficulty levels — timed, shuffled, and scored.
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