Sort ObservableCollection<string> through C#

Question

I have below ObservableCollection<string>. I need to sort this alphabetically.

private ObservableCollection<string> _animals = new ObservableCollection<string>
{
    "Cat", "Dog", "Bear", "Lion", "Mouse",
    "Horse", "Rat", "Elephant", "Kangaroo", "Lizard", 
    "Snake", "Frog", "Fish", "Butterfly", "Human", 
    "Cow", "Bumble Bee"
};

I tried _animals.OrderByDescending. But I don't know how to use it correctly.

_animals.OrderByDescending(a => a.<what_is_here_?>);

How can I do this?

Answer 1

Introduction

Basically, if there is a need to display a sorted collection, please consider using the CollectionViewSource class: assign ("bind") its Source property to the source collection — an instance of the ObservableCollection<T> class.

The idea is that CollectionViewSource class provides an instance of the CollectionView class. This is kind of "projection" of the original (source) collection, but with applied sorting, filtering, etc.

References:

• How to: Sort and Group Data Using a View in XAML.
• WPF’s CollectionViewSource.

Live Shaping

WPF 4.5 introduces "Live Shaping" feature for CollectionViewSource.

References:

• WPF 4.5 New Feature: Live Shaping.
• CollectionViewSource.IsLiveSorting Property.
• Repositioning data as the data's values change (Live shaping).

Solution

If there still a need to sort an instance of the ObservableCollection<T> class, here is how it can be done. The ObservableCollection<T> class itself does not have sort method. But, the collection could be re-created to have items sorted:

// Animals property setter must raise "property changed" event to notify binding clients.
// See INotifyPropertyChanged interface for details.
Animals = new ObservableCollection<string>
    {
        "Cat", "Dog", "Bear", "Lion", "Mouse",
        "Horse", "Rat", "Elephant", "Kangaroo",
        "Lizard", "Snake", "Frog", "Fish",
        "Butterfly", "Human", "Cow", "Bumble Bee"
    };
...
Animals = new ObservableCollection<string>(Animals.OrderBy(i => i));

Additional details

Please note that OrderBy() and OrderByDescending() methods (as other LINQ–extension methods) do not modify the source collection! They instead create a new sequence (i.e. a new instance of the class that implements IEnumerable<T> interface). Thus, it is necessary to re-create the collection.