List<T> OrderBy Alphabetical Order

SaaS_Developer_7215 0
Viewed 753668

I'm using C# on Framework 3.5. I'm looking to quickly sort a Generic List<T>. For the sake of this example, let's say I have a List of a Person type with a property of lastname. How would I sort this List using a lambda expression?

List<Person> people = PopulateList();
people.OrderBy(???? => ?????)
list sorting lambda generics c#
10 Answers

If you mean an in-place sort (i.e. the list is updated):

people.Sort((x, y) => string.Compare(x.LastName, y.LastName));

If you mean a new list:

var newList = people.OrderBy(x=>x.LastName).ToList(); // ToList optional
Marc_Gravell_233540

Do you need the list to be sorted in place, or just an ordered sequence of the contents of the list? The latter is easier:

var peopleInOrder = people.OrderBy(person => person.LastName);

To sort in place, you'd need an IComparer<Person> or a Comparison<Person>. For that, you may wish to consider ProjectionComparer in MiscUtil.

(I know I keep bringing MiscUtil up - it just keeps being relevant...)

user_226560 
people.OrderBy(person => person.lastname).ToList();
Danimal_27570

for me this useful dummy guide - Sorting in Generic List - worked. it helps you to understand 4 ways(overloads) to do this job with very complete and clear explanations and simple examples

  • List.Sort ()
  • List.Sort (Generic Comparison)
  • List.Sort (Generic IComparer)
  • List.Sort (Int32, Int32, Generic IComparer)
user_1845720

In .NET 7 preview you can use the simplified ordering of System.Linq. It also has some performance improvements.

var sorted = people.Order();

Also, be aware that the Sort method has a better performance in most cases because you don't allocate a new list.

user_26671730
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