IEnumerable vs List – What to Use? How do they work?

IEnumerable and List are both important concepts in C# for working with collections of data, but they serve different purposes and have different characteristics.

  1. IEnumerable:
    • IEnumerable is an interface in C# that represents a sequence of elements that can be enumerated or iterated over.
    • It provides a standard way to traverse and operate on collections without exposing the underlying implementation.
    • It defines a single method called GetEnumerator() that returns an IEnumerator object used to iterate over the elements.
    • By implementing IEnumerable, a class or collection allows consumers to use foreach loops and LINQ queries to work with the elements.
  2. List:
    • List is a generic class in C# that represents a dynamically resizable collection of elements.
    • It is part of the System.Collections.Generic namespace and provides various methods and properties for working with the collection.
    • List implements the IEnumerable<T> interface, meaning it can be enumerated using foreach loops and LINQ queries.
    • It provides additional functionality beyond simple enumeration, such as adding, removing, sorting, searching, and manipulating elements within the list.

Choosing between IEnumerable and List depends on the requirements of your specific scenario:

  • Use IEnumerable when:
    • You need to represent a sequence of elements but don’t require additional collection-specific operations beyond enumeration.
    • You want to provide a read-only view of a collection without exposing methods for modification.
    • You want to work with a collection in a generic or abstract manner, without relying on the specific implementation type.
  • Use List when:
    • You need a dynamically resizable collection that supports adding, removing, and modifying elements.
    • You require additional collection-specific operations like sorting, searching, or indexing.
    • You want to maintain a specific order of elements or need random access to elements by index.
    • You want to store a collection of items with duplicates and preserve the insertion order.

In terms of how they work, both IEnumerable and List allow you to iterate over the elements using foreach loops or LINQ queries. However, List provides additional methods and properties for managing and manipulating the collection, while IEnumerable is more focused on providing a standard way to traverse collections without exposing the underlying implementation details.

It’s important to note that List implements IEnumerable<T> and provides all the functionality of IEnumerable. Therefore, if you need the features provided by List, you can still use it as an IEnumerable when working with general enumeration scenarios.

Ultimately, the choice between IEnumerable and List depends on the specific requirements of your application, including the need for resizing, modification, ordering, and additional collection-specific operations.

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