linq Standard Query Operators Projection Operations
Example
Projection refers to the operations of transforming an object into a new form.
Select
Projects values that are based on a transform function.
Method Syntax
// Select var numbers = new int[] { 1, 2, 3, 4, 5 }; var strings = numbers.Select(n => n.ToString()); // strings = { "1", "2", "3", "4", "5" } Query Syntax
// select var numbers = new int[] { 1, 2, 3, 4, 5 }; var strings = from n in numbers select n.ToString(); // strings = { "1", "2", "3", "4", "5" } SelectMany
Projects sequences of values that are based on a transform function and then flattens them into one sequence.
Method Syntax
// SelectMany class Customer { public Order[] Orders { get; set; } } class Order { public Order(string desc) { Description = desc; } public string Description { get; set; } } ... var customers = new Customer[] { new Customer { Orders = new Order[] { new Order("O1"), new Order("O2") } }, new Customer { Orders = new Order[] { new Order("O3") } }, new Customer { Orders = new Order[] { new Order("O4") } }, }; var orders = customers.SelectMany(c => c.Orders); // orders = { Order("O1"), Order("O3"), Order("O3"), Order("O4") } Query Syntax
// multiples from var orders = from c in customers from o in c.Orders select o; // orders = { Order("O1"), Order("O3"), Order("O3"), Order("O4") } 
