I'm trying to create a method which (other than in name) shows that the ordering of some collection will be preserved.
I have considered SortedList, but dismissed it due to the requirement of holding a key. I have also dismissed other Sorted types for similar reasons, and SortedSet due to Linq returning IEnumerable instead of another SortedSet when you operate on it.
I don't mind if a new type is required, or I need to write methods in a specific way. The goal here is to highlight methods which preserve the input order of a collection when operating upon it.
I had thought about adding a custom attribute and just trusting that it will be used correctly, but I would ideally like to find something in the language which is more explicit.
-- Edit
It's not so much the order of the elements in the collection (I could use an IEnumerable), but some operation on the input collection. Let's say I were returning the root of all the numbers in an array, instead of returning (root, number)[], or (root, index)[] I want to return root[] and have it clear to the user that the order of the elements in the returned array matches the order of the elements in the input parameter.
No, there is nothing in C# or .Net that let you express and enforce "this method does not change order of elements in a collection / while iterating through collection".
Conventional expectation is order of elements stored in a collection preserved while iterating unless method/class explicitly named to indicate reordering.
Examples of "no reordering":
for / 'foreach`.Select, .First, .Take, .SelectMany, .WhereList, array.Examples of "does reordering"
List.Sort, List.Reverse.OrderBy, .ThenByHashSet, Dictionary, OrderedDictionary, SortedList