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List Methods | Additional Structures & File Handling
C# Beyond Basics
course content

Course Content

C# Beyond Basics

C# Beyond Basics

1. Additional Structures & File Handling
2. Structs & Enumerators
3. Introduction to Object-Oriented Programming (OOP)
4. OOP Essentials
5. OOP Principles

bookList Methods

In the previous chapter we learnt how to declare, initialize and add elements to a list. Additionally we also looked at how we would access elements of a list and loop through them. In this chapter we will look at some useful list methods.

1. Remove()

The Remove method removes the first instance of an element from a list.

Syntax: exampleList.remove(targetElement);

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using System; using System.Collections.Generic; namespace ConsoleApp { class Program { static void Main(string[] args) { List<string> fruits = new List<string> { "Apple", "Banana", "Orange", "Banana", "Grape" }; Console.Write("Before: "); foreach (string fruit in fruits) { Console.Write(fruit + " "); } fruits.Remove("Banana"); Console.Write("\nAfter: "); foreach (string fruit in fruits) { Console.Write(fruit + " "); } } } }

In case no such element is found, it simply doesn't do anything:

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using System; using System.Collections.Generic; namespace ConsoleApp { class Program { static void Main(string[] args) { List<string> fruits = new List<string> { "Apple", "Banana", "Orange", "Banana", "Grape" }; Console.Write("Before: "); foreach (string fruit in fruits) { Console.Write(fruit + " "); } fruits.Remove("some element"); // trying to remove an unknown element Console.Write("\nAfter: "); foreach (string fruit in fruits) { Console.Write(fruit + " "); } } } }

2. RemoteAt()

The RemoveAt method removes an element at a specific index.

Syntax: exampleList.RemoveAt(index);

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using System; using System.Collections.Generic; namespace ConsoleApp { class Program { static void Main(string[] args) { List<string> fruits = new List<string> { "Apple", "Orange", "Banana", "Grape" }; Console.Write("Before: "); foreach (string fruit in fruits) { Console.Write(fruit + " "); } fruits.RemoveAt(1); Console.Write("\nAfter: "); foreach (string fruit in fruits) { Console.Write(fruit + " "); } } } }

3. Clear

The Clear method simply removes all elements from a list. It takes no arguments.

Syntax: exampleList.Clear();

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using System; using System.Collections.Generic; namespace ConsoleApp { class Program { static void Main(string[] args) { List<string> fruits = new List<string> { "Apple", "Orange", "Banana", "Grape" }; Console.Write("Before: "); foreach (string fruit in fruits) { Console.Write(fruit + " "); } fruits.Clear(); Console.Write("\nAfter: "); foreach (string fruit in fruits) { Console.Write(fruit + " "); } } } }

4. Insert

The Insert method inserts an element in the list at a specified index.

Syntax: exampleList.Insert(index, elementToInsert);

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using System; using System.Collections.Generic; namespace ConsoleApp { class Program { static void Main(string[] args) { List<int> numbers = new List<int> { 2, 4, 6, 10, 12 }; Console.Write("Before: "); foreach (int number in numbers) Console.Write(number + " "); numbers.Insert(3, 8); Console.Write("\nAfter: "); foreach (int number in numbers) Console.Write(number + " "); } } }

We can omit the curly braces {} in case there's only a single statement inside an if-condition, a for-loop, or a foreach loop. For-example:

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foreach(int number in numbers) { Console.Write(number + " "); }

The above snippet is the same as:

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foreach(int number in numbers) Console.Write(number + " ");

If there's already an element at the specified index, it is pushed to the right, and so are the remaining elements of the array after it - in case there are any. The following diagram illustrates the process:

5. Contains()

The Contains method checks if a list contains a specific element. It returns a boolean value (true or false).

Syntax: exampleList.Contains(element);

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using System; using System.Collections.Generic; namespace ConsoleApp { class Program { static void Main(string[] args) { List<char> vowels = new List<char> { 'a', 'e', 'i', 'o', 'u' }; Console.WriteLine("Contains 'o': " + vowels.Contains('o')); } } }

6. IndexOf()

The IndexOf method returns the index of the first occurrence of an element in a list.

Syntax: exampleList.IndexOf(element);

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using System; using System.Collections.Generic; namespace ConsoleApp { class Program { static void Main(string[] args) { List<char> vowels = new List<char> { 'a', 'e', 'i', 'o', 'u' }; vowels.Remove('o'); Console.WriteLine("Index of 'o': " + vowels.IndexOf('o')); } } }

If the element doesn't exist in the list, it simply returns -1:

The indexOf method is especially useful when we want to access an element by index but we won't know it's index. For-example in the vowels, we want to access the element o by index and change it to capital O:

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using System; using System.Collections.Generic; namespace ConsoleApp { class Program { static void Main(string[] args) { List<char> vowels = new List<char> { 'a', 'e', 'i', 'o', 'u' }; int targetIndex = vowels.IndexOf('o'); Console.WriteLine(vowels[targetIndex]); vowels[targetIndex] = 'O'; Console.WriteLine(vowels[targetIndex]); } } }
1. What does the `Remove()` method do?
2. What is the fastest way of checking if a list contains a specific element?
3. Which method is used for removing all elements from a list?
4. What will be the output of the following code?
What does the `Remove()` method do?

What does the Remove() method do?

Select the correct answer

What is the fastest way of checking if a list contains a specific element?

What is the fastest way of checking if a list contains a specific element?

Select the correct answer

Which method is used for removing all elements from a list?

Which method is used for removing all elements from a list?

Select the correct answer

What will be the output of the following code?

What will be the output of the following code?

Select the correct answer

Everything was clear?

How can we improve it?

Thanks for your feedback!

Section 1. Chapter 3
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