I use LINQ to Objects instructions on an ordered array. Which operations shouldn\'t I do to be sure the order of the array is not changed?
If you are working on an array, it sounds like you are using LINQ-to-Objects, not SQL; can you confirm? Most LINQ operations don't re-order anything (the output will be in the same order as the input) - so don't apply another sort (OrderBy[Descending]/ThenBy[Descending]).
[edit: as Jon put more clearly; LINQ generally creates a new sequence, leaving the original data alone]
Note that pushing the data into a Dictionary<,> (ToDictionary) will scramble the data, as dictionary does not respect any particular sort order.
But most common things (Select, Where, Skip, Take) should be fine.