Which of the following is a reference type in C#?

The correct answer is C: class. Classes are reference types. byte, decimal are value types, and struct is also a value type.

Which of the following is true about properties in C#?

The correct answer is C: Properties provide encapsulation while maintaining clean syntax. Properties in C# allow controlled access to fields with validation logic while maintaining clean, intuitive syntax like field access.

A restaurant ordering system needs to ensure each order has a unique ID generated automatically. Which design pattern and feature should be used?

The correct answer is A: Static variable in Order class. Static variables are shared across all instances and can be used to generate unique IDs automatically without modifying external data.

What is the output of the following code? var dict = new Dictionary(); dict[1] = "A"; dict[1] = "B"; Console.WriteLine(dict[1]);

The correct answer is B: B. Using the indexer on Dictionary with an existing key updates the value, not throws. Output is 'B'.

What happens when you try to access an array element beyond its length in C#?

The correct answer is C: Throws IndexOutOfRangeException. Accessing an array index beyond its bounds throws an IndexOutOfRangeException at runtime.

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C# Programming
Collections

C# and .NET for campus placement

38 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 38

Topics in C# Programming

All Basics & Syntax 100 OOP in C# 100 Collections 71 ASP.NET Basics 19

Q.11 Medium Collections

Which scenario best uses Stack instead of Queue in a practical application?

A Processing network packets

B Undo/Redo functionality in editors

C Job scheduling

D Task queuing

Correct Answer: B. Undo/Redo functionality in editors

EXPLANATION

Stack<T> follows LIFO (Last-In-First-Out) principle, making it ideal for undo/redo functionality where the most recent action is reversed first.

Test

Q.12 Medium Collections

What does TryDequeue() return in ConcurrentQueue when the queue is empty?

A null

B false and sets output parameter to default

C Throws exception

D Returns empty value

Correct Answer: B. false and sets output parameter to default

EXPLANATION

TryDequeue() returns false if the queue is empty and sets the out parameter to the default value of T, avoiding exceptions.

Test

Q.13 Medium Collections

Which method allows you to get an element from a SortedSet at a specific index without using indexer?

A GetAt()

B ElementAt()

C Get()

D Retrieve()

Correct Answer: B. ElementAt()

EXPLANATION

ElementAt() is a LINQ method that retrieves an element at a specific index. SortedSet<T> doesn't support direct indexing.

Test

Q.14 Medium Collections

In a scenario with large datasets, which collection should you use to avoid boxing overhead?

A ArrayList

B Hashtable

C List

D SortedList

Correct Answer: C. List

EXPLANATION

List<T> is a generic collection that avoids boxing of value types, whereas ArrayList boxes all values, causing performance overhead.

Test

Q.15 Medium Collections

What happens when you enumerate a Dictionary during modification?

A It skips modified elements

B It throws InvalidOperationException

C It includes modified elements

D It pauses enumeration automatically

Correct Answer: B. It throws InvalidOperationException

EXPLANATION

Modifying a Dictionary<K,V> while enumerating throws InvalidOperationException. This is a safety feature to prevent undefined behavior.

Test

Q.16 Medium Collections

In C# 2024-25, which collection should be used for thread-safe operations without explicit locking?

A List

B ConcurrentBag

C Dictionary

D ArrayList

Correct Answer: B. ConcurrentBag

EXPLANATION

ConcurrentBag<T> from System.Collections.Concurrent provides thread-safe operations without explicit locking, suitable for multi-threaded scenarios.

Test

Q.17 Medium Collections

What is the primary advantage of using SortedList over SortedDictionary?

A Faster insertion and deletion

B Better memory efficiency for small collections

C Supports null keys

D Thread-safe operations

Correct Answer: B. Better memory efficiency for small collections

EXPLANATION

SortedList uses less memory than SortedDictionary but has slower insertion/deletion. SortedDictionary is better for frequent modifications.

Test

Q.18 Medium Collections

What is the time complexity of the IndexOf() method in List?

A O(1)

B O(log n)

C O(n)

D O(n log n)

Correct Answer: C. O(n)

EXPLANATION

IndexOf() performs a linear search through the list, resulting in O(n) time complexity in the worst case.

Test

Q.19 Medium Collections

Which collection type should be used when you need key-value pairs with guaranteed order of insertion?

A Hashtable

B Dictionary

C SortedDictionary

D OrderedDictionary

Correct Answer: D. OrderedDictionary

EXPLANATION

OrderedDictionary maintains insertion order for key-value pairs. Dictionary<K,V> does not guarantee order in older versions; SortedDictionary sorts by key.

Test

Q.20 Medium Collections

Which collection in C# maintains insertion order and allows fast removal from both ends?

A Deque

B LinkedList

C Queue

D SortedSet

Correct Answer: B. LinkedList

EXPLANATION

LinkedList<T> allows O(1) removal from both ends and maintains insertion order. Deque<T> is not a standard C# collection.

Test

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