Why collections over arrays in C Sharp (C#) - Challenge Your Understanding

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of modifying a List vs an Array

What will be the output of this C# code snippet?

C Sharp (C#)

int[] arr = {1, 2, 3};
var list = new List<int>(arr);
list.Add(4);
Console.WriteLine(arr.Length);
Console.WriteLine(list.Count);

A 3\n4

B 3\n3

C 4\n4

D 4\n3

💡 Hint

Remember that arrays have fixed size, but Lists can grow.

The array arr has a fixed length of 3. The List list is created from the array and then an element is added, so its count becomes 4. The array length remains 3.

🧠 Conceptual

intermediate

Why choose collections over arrays?

Which of the following is the main reason to prefer collections like List over arrays in C#?

A Arrays allow adding elements after creation, collections do not.

B Arrays support LINQ queries, collections do not.

C Collections are always faster than arrays.

D Collections can dynamically resize, arrays have fixed size.

💡 Hint

Think about flexibility in size.

Arrays have a fixed size once created. Collections like List can grow or shrink dynamically, making them more flexible for many scenarios.

❓ Predict Output

advanced

Output of modifying collection vs array reference

What will be the output of this C# code?

C Sharp (C#)

int[] arr = {10, 20, 30};
List<int> list = new List<int>(arr);
arr[0] = 100;
list[1] = 200;
Console.WriteLine(arr[0]);
Console.WriteLine(list[1]);

A 100\n200

B 10\n200

C 10\n20

D 100\n20

💡 Hint

Modifying the array changes its own elements; modifying the list changes its own copy.

The List is created as a copy of the array elements. Changing the array element at index 0 changes arr[0]. Changing the list element at index 1 changes list[1]. They are independent after creation.

🔧 Debug

advanced

Identify the error when resizing an array

What error will this C# code produce?

C Sharp (C#)

int[] arr = new int[3];
arr[3] = 10;

A NullReferenceException

B IndexOutOfRangeException

C SyntaxError

D No error, runs fine

💡 Hint

Array indices start at 0 and go up to length-1.

The array has length 3, so valid indices are 0, 1, and 2. Accessing index 3 is out of range and causes an IndexOutOfRangeException.

🚀 Application

expert

Choosing the right data structure for dynamic data

You need to store a list of user names that can grow and shrink during program execution. Which is the best choice in C#?

A Use a string[] array because it is faster to access.

B Use a Dictionary<int, string> to store user names by index.

C Use a List<string> because it can dynamically resize.

D Use a fixed size array and create a new one when resizing is needed.

💡 Hint

Think about ease of adding and removing elements.

List<string> is designed to grow and shrink dynamically, making it the best choice for a changing list of user names. Arrays have fixed size and require manual resizing.