Which method in Stack returns the top element without removing it?

The correct answer is B: Peek(). Peek() returns the top element without removal. Pop() removes it. Top() and Get() are not Stack methods.

What is the default access modifier for a class member in C# if not explicitly specified?

The correct answer is B: private. The default access modifier for class members in C# is 'private'. This means the member is only accessible within the same class unless explicitly specified otherwise.

Which of the following correctly describes method overloading in C#?

The correct answer is B: Methods can have the same name with different parameter types, count, or order. Method overloading allows same method name with different signatures (parameter types, count, or order). Return type alone cannot differentiate overloaded methods.

An e-commerce system needs to ensure that a Product class cannot be instantiated directly but can be inherited. Additionally, it must define some concrete methods and some abstract methods. Which approach is best?

The correct answer is C: Use an Abstract Class. Abstract classes can have both concrete (implemented) and abstract (unimplemented) methods. They cannot be instantiated directly but can be inherited. This perfectly fits the requirement.

In a real-time data processing application, which concurrent collection would be best for producer-consumer pattern?

The correct answer is B: BlockingCollection. BlockingCollection supports blocking operations for producer-consumer patterns, allowing threads to wait for items or space.

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C# Programming
Collections

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38 Q 4 Topics Take Mock Test

Difficulty: All Easy Medium Hard 31–38 of 38

Topics in C# Programming

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

Q.31 Medium Collections

Which collection should be used when you need sorted key-value pairs automatically?

A Dictionary

B SortedDictionary

C List

D Hashtable

Correct Answer: B. SortedDictionary

EXPLANATION

SortedDictionary<K,V> automatically maintains keys in sorted order. Dictionary<K,V> maintains insertion order but not sorted order.

Test

Q.32 Medium Collections

Consider: Dictionary dict = new(); dict.Add("a", 1); dict.Add("a", 2); What happens?

A Value is updated to 2

B ArgumentException is thrown

C Both values are stored

D The second add is ignored

Correct Answer: B. ArgumentException is thrown

EXPLANATION

Dictionary enforces unique keys. Attempting to add a duplicate key throws ArgumentException. Use dict["a"] = 2 to update.

Test

Q.33 Medium Collections

What is the difference between Stack.Push() and Stack.Pop()?

A Push adds, Pop removes and returns the element

B Pop adds, Push removes and returns the element

C Both are identical operations

D Push returns a value, Pop doesn't

Correct Answer: A. Push adds, Pop removes and returns the element

EXPLANATION

Push() adds an element to the stack, while Pop() removes and returns the top element. If stack is empty, Pop throws InvalidOperationException.

Test

Q.34 Medium Collections

Which interface must be implemented to use a collection in a foreach loop?

A IEnumerable

B ICollection

C IList

D IComparable

Correct Answer: A. IEnumerable

EXPLANATION

IEnumerable interface provides GetEnumerator() method, enabling foreach iteration. IEnumerable<T> is the generic version.

Test

Q.35 Medium Collections

What happens when you try to access an index beyond the Count in a List?

A Returns null

B Returns the last element

C Throws IndexOutOfRangeException

D Returns default value of type

Correct Answer: C. Throws IndexOutOfRangeException

EXPLANATION

Accessing an invalid index throws IndexOutOfRangeException. This is a runtime error that must be caught to prevent program crashes.

Test

Q.36 Medium Collections

Which collection maintains insertion order but uses a hash table for faster lookups?

A Dictionary

B SortedDictionary

C LinkedHashMap (not in C#)

D Both A and B

Correct Answer: A. Dictionary

EXPLANATION

Dictionary<K,V> in .NET maintains insertion order (in recent versions) and provides O(1) lookup. SortedDictionary maintains sorted order instead.

Test

Q.37 Medium Collections

What is the time complexity of accessing an element by index in a List?

A O(n)

B O(log n)

C O(1)

D O(n log n)

Correct Answer: C. O(1)

EXPLANATION

List<T> is backed by an array, allowing direct index-based access in constant time O(1).

Test

Q.38 Medium Collections

Which method removes all elements from a collection in C#?

A Remove()

B RemoveAt()

C Clear()

D Delete()

Correct Answer: C. Clear()

EXPLANATION

Clear() removes all elements from a collection. Remove() removes a specific element, and RemoveAt() removes an element at a specific index.

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