How to check if a list is ordered?

Question

I am doing some unit tests and I want to know if there's any way to test if a list is ordered by a property of the objects it contains.

Right now I am doing it this way but I don't like it, I want a better way. Can somebody help me please?

// (fill the list)
List<StudyFeedItem> studyFeeds = 
    Feeds.GetStudyFeeds(2120, DateTime.Today.AddDays(-200), 20);   

StudyFeedItem previous = studyFeeds.First();

foreach (StudyFeedItem item in studyFeeds)
{
    if (item != previous)
    {
        Assert.IsTrue(previous.Date > item.Date);
    }

    previous = item;
}

Answer 1

If you are using MSTest, you may want to take a look at CollectionAssert.AreEqual.

Enumerable.SequenceEqual may be another useful API to use in an assertion.

In both cases you should prepare a list that holds the expected list in the expected order, and then compare that list to the result.

Here's an example:

var studyFeeds = Feeds.GetStudyFeeds(2120, DateTime.Today.AddDays(-200), 20);   
var expectedList = studyFeeds.OrderByDescending(x => x.Date);
Assert.IsTrue(expectedList.SequenceEqual(studyFeeds));