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07 Feb 2024

Intermediate

IEnumerable, ICollection, IList, and IDictionary are interfaces in the .NET framework that provide different levels of functionality for working with collections of objects.

IEnumerable<T>:

IEnumerable<T> is the most basic interface for .NET collections. It represents a forward-only cursor for a collection, enabling you to iterate over a collection of a specific type. It provides a single method, GetEnumerator(), which returns an IEnumerator<T> that allows you to iterate through the collection.

Uses:

  1. Iterating over collections using foreach loops.
  2. LINQ queries - LINQ extends IEnumerable<T> to provide powerful querying capabilities over collections.

Example:

IEnumerable<int> numbers = new List<int> { 1, 2, 3, 4, 5 };
foreach (var number in numbers)
{
    Console.WriteLine(number);
}

ICollection<T>:

ICollection<T> extends IEnumerable<T> and adds methods to add, remove, and check for the presence of elements in the collection. It represents a generic collection of objects and is more feature-rich than IEnumerable<T>.

Uses:

  1. Adding and removing elements from a collection.
  2. Checking the count of elements in a collection.

Example:

ICollection<string> names = new List<string>();
names.Add("John");
names.Add("Jane");
names.Remove("John");
Console.WriteLine($"Count: {names.Count}");

IList<T>:

IList<T> extends ICollection<T> and adds methods to access and modify elements by index. It represents a non-generic list of objects that can be accessed by index.

Uses:

  1. Accessing and modifying elements by index.
  2. Performing operations like sorting, searching, and inserting elements at specific positions.

Example:

IList<int> numbers = new List<int> { 1, 2, 3, 4, 5 };
Console.WriteLine(numbers[2]); // Output: 3
numbers.Insert(2, 10);
Console.WriteLine(string.Join(", ", numbers)); // Output: 1, 2, 10, 3, 4, 5

IDictionary<TKey, TValue>:

IDictionary<TKey, TValue> represents a generic collection of key-value pairs. It provides methods to add, remove, and search for elements by key.

Uses:

  1. Associating unique keys with values for efficient retrieval.
  2. Performing dictionary-style operations like adding, removing, and updating key-value pairs.

Example:

IDictionary<string, int> ages = new Dictionary<string, int>();
ages.Add("John", 30);
ages.Add("Jane", 25);
ages["John"] = 32;
Console.WriteLine($"John's age: {ages["John"]}");

These interfaces provide common patterns for handling collections in .NET and are fundamental to understanding and working with collections effectively in C#.

c-sharp
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