Зміст курсу

C# Beyond Basics

1. Additional Structures & File Handling

What are Lists?Practicing List Declaration List Methods What are Dictionaries?Practicing Dictionaries Reading Files using StreamReader Reading Files using File Methods Writing Files Error Handling Practicing Error Handling

2. Structs & Enumerators

What are Structs?Defining & Using a Structure Practicing Structs Structs with Other Data Structures Struct Methods Correctly Accessing Fields in Struct Methods Practicing Methods Struct Constructors Practicing Constructors Enumerators Practicing Enumerator

3. Introduction to Object-Oriented Programming (OOP)

What is Object-Oriented Programming?Defining Classes Practice: Creating Classes Class Objects Class Objects vs Struct Objects Practice: Objects Class Methods Practice: Methods Class Constructors Practice: Constructors

4. OOP Essentials

Derived Classes Derived Classes Practice Common Access Modifiers Access Modifiers Practice The `static` Keyword Practicing `static` Keyword Method Overloading Method Overloading Practice

5. OOP Principles

What are the Principles of OOP?Inheritance Practicing Inheritance Polymorphism Practicing Polymorphism Encapsulation Encapsulation Practice Abstraction Abstraction Practice What's Next?

List 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);

index


              123456789101112131415161718192021222324252627
            
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:

index


              123456789101112131415161718192021222324252627
            
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);

index


              123456789101112131415161718192021222324252627
            
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();

index


              123456789101112131415161718192021222324252627
            
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);

index


              1234567891011121314151617181920212223
            
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:

index


              123
            
foreach(int number in numbers) {
    Console.Write(number + " ");
}

The above snippet is the same as:

index


              12
            
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);

index


              1234567891011121314
            
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);

index


              123456789101112131415
            
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:

index


              12345678910111213141516171819
            
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]);
        }
    }
}

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