Linq statement to iterate through a collection and making sure each item is in the correct order?

Question

Hi folks,

i'm got a simple IEnumerable<foo> foos; This collection are some results from a db call.

I wish to make sure that each item in the list is ordered correctly. The Db either returns the results by

• ordered by id, lowest to highest. eg. 1, 2, 3, 4,. ... etc.
• ordered by date created, decrement (most recent, first).

Can this be done with a quick linq statement .. to check for this?

eg. Assert.IsTrue(.. insert linq statement here .. )

currently, i've got a for loop and remember the previous entry and check if the value of that, if there was a value. This feels ... cumbersome.

Any ideas?

Answer 1

You could compare your collection to an ordered version:

CollectionAssert.AreEqual(foos.ToList(), foos.OrderBy(f => f.Id));

Or:

CollectionAssert.AreEqual(foos.ToList(), 
                          foos.OrderByDescending(f => f.DateCreated));

Answer 2

There is an extension method called SequenceEqual which will do that. However, there is also an assert method called CollectionAssert.AreEqual that compares two collections to ensure they have the same items in the same order.