What are Add, Remove methods in C# lists?

The List<T> is a generic collection in C# that provides dynamic array functionality. The Add() and Remove() methods are fundamental operations for managing elements in a list, allowing you to add new items and remove existing ones efficiently.

Syntax

Following is the syntax for adding elements to a list −

List<T> listName = new List<T>();
listName.Add(item);

Following is the syntax for removing elements from a list −

bool result = listName.Remove(item);
listName.RemoveAt(index);

Using Add() Method

The Add() method appends an element to the end of the list. It increases the list size by one and returns void −

using System;
using System.Collections.Generic;

class Program {
    static void Main() {
        List<string> sports = new List<string>();
        sports.Add("Football");
        sports.Add("Tennis");
        sports.Add("Soccer");
        
        Console.WriteLine("Sports List:");
        foreach (string s in sports) {
            Console.WriteLine(s);
        }
        Console.WriteLine("Total items: " + sports.Count);
    }
}

The output of the above code is −

Sports List:
Football
Tennis
Soccer
Total items: 3

Using Remove() Method

The Remove() method removes the first occurrence of a specific object from the list. It returns true if the item was successfully removed, or false if the item was not found −

using System;
using System.Collections.Generic;

class Program {
    static void Main() {
        List<string> sports = new List<string>();
        sports.Add("Football");
        sports.Add("Tennis");
        sports.Add("Soccer");
        
        Console.WriteLine("Original List:");
        foreach (string s in sports) {
            Console.WriteLine(s);
        }
        
        bool removed = sports.Remove("Tennis");
        Console.WriteLine("Remove 'Tennis': " + removed);
        
        Console.WriteLine("\nUpdated List:");
        foreach (string s in sports) {
            Console.WriteLine(s);
        }
    }
}

The output of the above code is −

Original List:
Football
Tennis
Soccer
Remove 'Tennis': True

Updated List:
Football
Soccer

Using RemoveAt() Method

The RemoveAt() method removes the element at a specific index. This is useful when you know the position of the element to remove −

using System;
using System.Collections.Generic;

class Program {
    static void Main() {
        List<int> numbers = new List<int> {10, 20, 30, 40, 50};
        
        Console.WriteLine("Original List:");
        for (int i = 0; i < numbers.Count; i++) {
            Console.WriteLine($"Index {i}: {numbers[i]}");
        }
        
        numbers.RemoveAt(2); // Remove element at index 2 (value 30)
        
        Console.WriteLine("\nAfter RemoveAt(2):");
        for (int i = 0; i < numbers.Count; i++) {
            Console.WriteLine($"Index {i}: {numbers[i]}");
        }
    }
}

The output of the above code is −

Original List:
Index 0: 10
Index 1: 20
Index 2: 30
Index 3: 40
Index 4: 50

After RemoveAt(2):
Index 0: 10
Index 1: 20
Index 2: 40
Index 3: 50

Comparison of List Methods

Conclusion

The Add() and Remove() methods are essential for managing List<T> collections in C#. Add() appends elements to the end, while Remove() finds and removes the first matching element. Use RemoveAt() when you need to remove an element at a specific index position.