What is missing in this selection strategy, which C # collection to use?

Question

Here is my strategy for choosing the type of use of C #:

• if the number of elements in the collection is fixed, then use an array , for example:

  string [] direction = new string [] {"north", "south", "east", "west"};

• otherwise always use List<T>

• unless, of course, you need a more specialized collection, for example. Stack<T>, Queue<T>, or Dictionary<TKey, TValue>

• but never again use an ArrayList

Based on your experience, what is missing from this strategy?

Answer 1

Your rules work fine.

Besides:

• Always pass general (or specialized) collections to non-viable ( object ) collections.
• Use HashSet<T> if you want to check only the existence, and not the mapping of key values ​​(which is represented through the Dictionary ).
• For dictionaries, consider using ordered maps ( SortedList<...> , SortedDictionary<...> ) if ordering seems important.
• Use linked lists if you have delete / paste operations in the middle.

and, of course, the most important:

• Never export concrete collection types: always use the most common interface, which - in most cases - IList<T> or IEnumerable<T> .

Answer 2

I would say that in most cases, even if I knew the number of elements in the collection, I would use List, simply for the number of function functions that it provides, and LINQ compatibility.

Hashmaps are an important use case when you need faster access to items in a collection.

Answer 3

You can also use Collection<T> if you plan to override the add / remove / clean methods in the inherited class, since there are virtual methods.