Generics

Question 1

With generics what can you do?

Answer 1

With generics, you can create classes and methods that are
independent of contained types.

Question 2

What is generics?

Answer 2

Generics in C# allow you to define classes, methods, delegates, and interfaces with a placeholder for the type of data they store or use.

Question 3

What are the benefits of generics?

Answer 3

Code reusability, type safety, and performance are benefits.

Question 4

Value types are stored on the ______, reference types are stored on the ______.

Answer 4

stack, heap.

Question 5

What is boxing?

Answer 5

The conversion from a value type to a reference type is known as boxing.

Question 6

What is unboxing?

Answer 6

When a boxed value type can be converted to a value type.

With unboxing, the cast operator is required.

Question 7

Is an array size static?

Answer 7

An array’s size is set at compile-time and is static

Question 8

How is an ArrayList different from arrays?

Answer 8

• Items can be added and removed dynamically, and the ArrayList resizes itself.
• ArrayList belongs to System.Collections namespace.
• Add() method can be used to add items.
• ArrayList is not type-safe.

Question 9

What are some benefits of generic lists compared to arrays and arraylists?

Answer 9

• List<T> stores elements of the specified type and it grows automatically.</T>
• List<T> can store multiple null and duplicate elements.</T>
• List<T> can be accessed using indexer, for loop or foreach statement.</T>
• LINQ can be used to query List<T> collection.</T>
• List<T> is ideal for storing and retrieving large number of elements.</T>

Question 10

What’s the syntax to create a default constructor for an empty list?

Answer 10

List<int> myList = new List<int>();</int></int>

Question 11

What’s the syntax to create a default constructor for a list with a capacity of 10?

Answer 11

List<int> myList = new List<int>(10);</int></int>

Question 12

What does this code do?

Answer 12

Sets the myList capacity to 20.

Question 13

What does this code do?

Answer 13

TrimExcess removes the unneeded capacity. However, because the relocation takes time, TrimExcess has no effect if the item count is more than 90 percent of capacity.

Question 14

What does this code do?

Answer 14

Creates a list of int type and assigns it values and then prints “Total elements: “ and the count of all the elements.

Question 15

Create the code for a foreach loop that iterates through the items in myList and prints the item

Answer 15

foreach (var item in myList)
Console.WriteLine(item);

Question 16

Create the code for a foreach method that iterates through the items in myList and prints the item

Answer 16

myList.ForEach(item => Console.WriteLine(item));

Question 17

Create the code for a for loop that iterates through the items in myList and prints the item

Answer 17

for (int i=0; i<myList.Count; i++)
Console.WriteLine(myList[i]);

Question 18

What is the syntax for the insert method?

Answer 18

list_name.Insert(int index, T item);

Question 18

What is the syntax for the remove method?

Answer 18

list_name.Remove(T item);

Question 19

What is the syntax for the removeAt method?

Answer 19

list_name.RemoveAt(int index);

Question 20

What is IndexOf?

Answer 20

The method IndexOf requires an object as parameter and returns the index of the first occurrence of the item if it is found inside the collection.

If the item is not found, -1 is returned.

Question 21

What is the contains method?

Answer 21

The method Contains requires an object as parameter and returns true if the item is found inside the collection.

If the item is not found, false is returned.

Question 22

What is the find method?

Answer 22

The method Find requires a predicate match or a lambda expression as parameter and returns the object itself if it is found inside the collection.

If the object is not found, null is returned.

Question 23

What is a dictionary?

Answer 23

is a generic collection that stores key-value pairs. It provides fast lookups, additions, and removals of elements by their keys. The TKey represents the type of keys in the dictionary, and TValue represents the type of values.

Question 24

What does the ContainsKey() method do?

Answer 24

Checks if a key exists in the dictionary.

Question 25

What is the syntax for a dictionary named myDictionary that takes in int as a key and string as it’s value?

Answer 25

Dictionary<int, string> myDictionary = new Dictionary<int, string>();

Question 26

What is a queue?

Answer 26

A queue is a collection whose elements are processed first-in-first-out (FIFO).

Question 27

Can you access queue elements using an indexer?

Answer 27

False.

Question 28

What is the enqueue method?

Answer 28

A method that allows you to add an item to it, which is put at the end of the queue.

Question 29

What is the dequeue method?

Answer 29

A method to get items from the beginning of the queue.

Question 30

What is a stack?

Answer 30

The item that is added last to the stack is read first, so the stack is a last-in-first-out (LIFO) container.

Question 31

What method adds an item to the stack?

Answer 31

Push.

Question 32

What method removes the item that was added last?

Answer 32

Pop.