System.Collections.Generic Namespace

Namespace: System.Collections.Generic

Assembly: mscorlib.dll (in .NET Framework 4.8)

Contains interfaces and classes that define highly scalable data structures, such as lists, queues, dictionaries, and sets.

Classes

Interfaces

Common Usage Examples

Using List<T>

The List<T> class represents a strongly typed list of objects that can be accessed by index. It provides methods for adding, removing, searching, and sorting elements.


                        // Declare and initialize a list of strings
                        List<string> names = new List<string>();
                        names.Add("Alice");
                        names.Add("Bob");
                        names.Add("Charlie");

                        // Iterate through the list
                        foreach (string name in names)
                        {
                            Console.WriteLine(name);
                        }

                        // Access an element by index
                        Console.WriteLine(names[0]); // Output: Alice

Using Dictionary<TKey, TValue>

The Dictionary<TKey, TValue> class stores key-value pairs. It provides efficient lookup, insertion, and deletion of elements based on their keys.


                        // Declare and initialize a dictionary of integers and strings
                        Dictionary<int, string> studentGrades = new Dictionary<int, string>();
                        studentGrades.Add(101, "Alice");
                        studentGrades.Add(102, "Bob");
                        studentGrades.Add(103, "Charlie");

                        // Access a value by key
                        Console.WriteLine(studentGrades[102]); // Output: Bob

                        // Check if a key exists
                        if (studentGrades.ContainsKey(101))
                        {
                            Console.WriteLine("Student 101 found.");
                        }

Using HashSet<T>

The HashSet<T> class stores a collection of unique elements. It provides efficient methods for adding, removing, and checking for the existence of elements, without duplicates.


                        // Declare and initialize a hash set of integers
                        HashSet<int> uniqueNumbers = new HashSet<int>();
                        uniqueNumbers.Add(1);
                        uniqueNumbers.Add(5);
                        uniqueNumbers.Add(2);
                        uniqueNumbers.Add(1); // This will be ignored as it's a duplicate

                        // Check for element existence
                        if (uniqueNumbers.Contains(5))
                        {
                            Console.WriteLine("5 is in the set.");
                        }