Question

I want to write a lambda expression to verify that a list is ordered correctly. I have a List where a person has a Name property eg:

IList<Person> people = new List<Person>(); people.Add(new Person(){ Name = 'Alan'}); people.Add(new Person(){ Name = 'Bob'}); people.Add(new Person(){ Name = 'Chris'}); 

I’m trying to test that the list is ordered ASC by the Name property.So I’m after something like

Assert.That(people.All(....), 'list of person not ordered correctly'); 

How can I write a lambda to check that each Person in the list has a name less that the next person in the list?

Answer 1

Here’s an alternative to Jared’s solution – it’s pretty much the same, but using a foreach loop and a Boolean variable to check whether or not this is the first iteration. I usually find that easier than iterating manually:

public static bool IsOrdered<T>(this IEnumerable<T> source) {   var comparer = Comparer<T>.Default;   T previous = default(T);   bool first = true;    foreach (T element in source)   {       if (!first && comparer.Compare(previous, element) > 0)       {           return false;       }       first = false;       previous = element;   }   return true; }