Photo by Pau Casals on Unsplash LINQ methods (All, Contains, SequenceEqual) in this article are somehow related in a way that they are predicates (returns true or false).
Here are the methods covered so far.
- Part 1 〰️ Select, Aggregate, Where, OrderBy (Ascending, Descending)
- Part 2 〰️ Any, Distinct, Concat, SelectMany
- Part 3 〰️ Reverse, Zip, Min/Max
- Part 4 〰️ Union, Intersect, Except
- Part 5 〰️ Sum, Average, Count
- Part 6 〰️ First, Last, DefaultIfEmpty, Skip, Take
- Part 7 〰️ Empty, Repeat, Range
- Part 8 〰️ All, Contains, SequenceEqual
🔴 Overview
In this article, I will cover following methods.
[table id=9 /]
The sample collections used in this part are shown as below.
C#
| private static List<Order> Orders = new List<Order>{ | |
| new Order(id: 1, quantity: 40, orderDate: new DateTime(2018, 1,1,1,1,1,1)), | |
| new Order(id: 2, quantity: 20, orderDate: new DateTime(2018, 2,2,2,2,2,2)), | |
| new Order(id: 3, quantity: 30, orderDate: new DateTime(2018, 3,3,3,3,3,3)), | |
| new Order(id: 4, quantity: 10, orderDate: new DateTime(2018, 4,4,4,4,4,4)), | |
| new Order(id: 5, quantity: 20, orderDate: new DateTime(2018, 5,5,5,5,5,5)), | |
| }; | |
| private static List<Order> DomesticOrders = new List<Order>{ | |
| new Order(id: 1, quantity: 40, orderDate: new DateTime(2018, 1,1,1,1,1,1)), | |
| new Order(id: 11, quantity: 20, orderDate: new DateTime(2018, 11,2,2,2,2,2)), | |
| new Order(id: 111, quantity: 450, orderDate: new DateTime(2018, 11,1,2,2,2,2)), | |
| new Order(id: 1111, quantity: 230, orderDate: new DateTime(2018, 11,11,2,2,2,2)), | |
| }; |
JavaScript
| const orders = [ | |
| { id: 1, quantity: 40, orderDate: new Date(2018, 1, 1, 1, 1, 1) }, | |
| { id: 2, quantity: 20, orderDate: new Date(2018, 2, 2, 2, 2, 2) }, | |
| { id: 3, quantity: 30, orderDate: new Date(2018, 3, 3, 3, 3, 3) }, | |
| { id: 4, quantity: 10, orderDate: new Date(2018, 4, 4, 4, 4, 4) }, | |
| { id: 5, quantity: 20, orderDate: new Date(2018, 5, 5, 5, 5, 5) } | |
| ]; | |
| const domesticOrders = [ | |
| { id: 1, quantity: 40, orderDate: new Date(2018, 1, 1, 1, 1, 1) }, | |
| { id: 11, quantity: 20, orderDate: new Date(2018, 11, 2, 2, 2, 2) }, | |
| { id: 111, quantity: 450, orderDate: new Date(2018, 11, 1, 2, 2, 2) }, | |
| { id: 1111, quantity: 230, orderDate: new Date(2018, 11, 11, 2, 2, 2) } | |
| ]; |
🔴 Examples
🔸 All
JavaScript has a method called Array#every, which works the same way as All does.
| private static void AllDemo(List<Order> orders) | |
| { | |
| var areAllOrdersPlacedOn2018 = orders.All(order => order.OrderDate.Year == 2018); | |
| WriteLine($"Are All Orders Placed On 2018?: {areAllOrdersPlacedOn2018}"); | |
| } |
| function allDemo(orders) { | |
| const areAllOrdersPlacedOn2018 = orders.every( | |
| order => order.orderDate.getFullYear() === 2018 | |
| ); | |
| WriteLine(`Are All Orders Placed On 2018?: ${areAllOrdersPlacedOn2018}`); | |
| } |
Results
| // C# | |
| ==================== All DEMO - Check If All Orders Match a Condition ==================== | |
| Are All Orders Placed On 2018?: True | |
| // JS | |
| ==================== All DEMO - Check If All Orders Match a Condition ==================== | |
| Are All Orders Placed On 2018?: true |
every is more flexible as the callback is also passed an index.
🔸 Contains
There are so many ways implement contains but i used some as it short circuits (returns as soon as a condition is met).
| private static void ContainsDemo(List<Order> shippedOrders, List<Order> domesticOrders) | |
| { | |
| var firstDomesticOrder = domesticOrders.First(); | |
| var containsDomesticOrder = shippedOrders.Contains(firstDomesticOrder, new OrderEqualityCompaprer()); | |
| WriteLine($"Is the first domestic order shipped? {containsDomesticOrder}"); | |
| } |
| function containsDemo(shippedOrders, domesticOrders) { | |
| const firstDomesticOrder = domesticOrders[0]; | |
| const equalityComparer = order => order.id === firstDomesticOrder.id; | |
| const containsDomesticOrder = shippedOrders.some(equalityComparer); | |
| WriteLine(`Is the first domestic order shipped? ${containsDomesticOrder}`); | |
| } |
Results
| // C# | |
| ==================== Contains DEMO - Do Shipped Orders Contain a Domestic Order? ==================== | |
| Is the first domestic order shipped? True | |
| // JS | |
| ==================== Contains DEMO - Do Shipped Orders Contain a Domestic Order? ==================== | |
| Is the first domestic order shipped? true |
OrderEqualityComparer object instance simply checks if two objects are the same by an ID. JavaScript version simply passes a callback which does the same.
🔸 SequenceEqual
You can use every here to check if two sequences are the same as every passes an index of current element to the callback.
| private static void SequenceEqualDemo(List<Order> shippedOrders, List<Order> domesticOrders) | |
| { | |
| var sameOrderAreSame = shippedOrders.SequenceEqual(shippedOrders); | |
| WriteLine($"Same Orders share the same sequence {sameOrderAreSame}"); | |
| var areAllDomesticOrdersShipped = shippedOrders.SequenceEqual(domesticOrders); | |
| WriteLine($"Are All Domestic Order Shipped? {areAllDomesticOrdersShipped}"); | |
| } |
| function sequenceEqualDemo(shippedOrders, domesticOrders) { | |
| const sameOrderAreSame = shippedOrders.every( | |
| (order, i) => order.id === shippedOrders[i].id | |
| ); | |
| WriteLine(`Same Orders share the same sequence ${sameOrderAreSame}`); | |
| const areAllDomesticOrdersShipped = shippedOrders.every( | |
| (order, i) => order.id === domesticOrders[i].id | |
| ); | |
| WriteLine(`Are All Domestic Order Shipped? ${areAllDomesticOrdersShipped}`); | |
| } |
Results
| // C# | |
| ==================== SequenceEqual DEMO - Check If Two Sequences Are The Same ==================== | |
| Same Orders share the same sequence True | |
| Are All Domestic Order Shipped? False | |
| // JS | |
| ==================== SequenceEqual DEMO - Check If Two Sequences Are The Same ==================== | |
| Same Orders share the same sequence true | |
| Are All Domestic Order Shipped? false |
🔴 Closing Remark
I hope this article can serve as a cheat sheet (that's how I started this series).
Please let me know should you find any errors or improvements I can make to the codes. The full source code and instructions on how to run them are on GitHub.