Corresponds to the ThenByDescending extension method within the System.Linq namespace. This method performs a subsequent ordering of elements in a sequence in descending order, according to a key selector function.
public static IEnumerable<TSource> ThenByDescending<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
An IEnumerable<TSource> whose elements to order.
A function to extract a key from each element. The comparison is performed on the keys.
An IOrderedEnumerable<TSource> that contains elements from the input sequence ordered by key in descending order.
The ThenByDescending method is used to perform a secondary sort operation on a sequence that has already been sorted by using OrderBy or OrderByDescending.
If the initial sort operation was not a descending sort, ThenByDescending will apply a descending sort for the secondary sort criterion.
If the sequence is not sorted by OrderBy or OrderByDescending before calling ThenByDescending, the behavior is equivalent to calling OrderByDescending with the specified key selector.
// Sample data
var people = new List<Person> {
new Person { Name = "Alice", Age = 30 },
new Person { Name = "Bob", Age = 25 },
new Person { Name = "Charlie", Age = 30 },
new Person { Name = "David", Age = 25 }
};
// Sort by Age descending, then by Name descending
var sortedPeople = people
.OrderByDescending(p => p.Age)
.ThenByDescending(p => p.Name)
.ToList();
// Output the sorted names and ages
foreach (var person in sortedPeople)
{
// Console.WriteLine($"{person.Name} ({person.Age})");
}
// Expected Output:
// Charlie (30)
// Alice (30)
// David (25)
// Bob (25)
var products = new List<Product> {
new Product { Name = "Laptop", Category = "Electronics", Price = 1200.00m },
new Product { Name = "Keyboard", Category = "Electronics", Price = 75.00m },
new Product { Name = "Desk", Category = "Furniture", Price = 300.00m },
new Product { Name = "Chair", Category = "Furniture", Price = 150.00m }
};
// Sort by Category ascending, then by Price descending
var sortedProducts = products
.OrderBy(p => p.Category)
.ThenByDescending(p => p.Price)
.ToList();
// Output the sorted products
foreach (var product in sortedProducts)
{
// Console.WriteLine($$"{product.Name} ({product.Category}, {product.Price:C})");
}
// Expected Output:
// Laptop (Electronics, $1,200.00)
// Keyboard (Electronics, $75.00)
// Desk (Furniture, $300.00)
// Chair (Furniture, $150.00)