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c#generic-collections

Implementing my own generic collection in C#

I am trying to write my own generic collection (List<T>) in C# but got confused with the interfaces. As I understand, in order to create my own collection, I need to implement several interfaces, like ICollection, IList, IEnumerator, IEnumerable etc. But I can't really understand which ones I need. Thanks in advance

Solution

  • You have to implement IList<T> for access to the collection's items by their index. IList<T> inherits from ICollection<T>, IEnumerable<T> and IEnumerable, so you get those anyway.

    For a more basic collection without access to an item by index, you implement ICollection<T>, which comes with IEnumerable<T> and IEnumerable through inheritance.

    You can additionally implement IReadOnlyList<T> (or IReadOnlyCollection<T> respectively), but that is usually not necessary.

    You should also look into inheriting from System.Collections.ObjectModel.Collection<T> instead, which is the recommended way, because the usual boilerplate interface implementations are already done for you and you can concentrate on the parts that make your collection special.