static void Main(string[] args)
{
var books = new BookRepository().GetBooks();
//without linq
//var cheapBooks = new List<Book>();
//foreach (var book in books)
//{
// if (book.Price < 10)
// cheapBooks.Add(book);
//}
//with linq Extension methods:
var cheapBooks = books.Where(b => b.Price < 10).OrderBy(b => b.Title); //can chain linq!
//.Select is used for "projections" or "transformations".
//the below code transforms a list of books into a list of strings.
var cheapBooksTitleString = books.Select(b => b.Title);
//more reader-friendly layout:
var readerFriendly = books
.Where(b => b.Price < 10)
.OrderBy(b => b.Title)
.Select(b => b.Title);
foreach (var book in cheapBooks)
{
Console.WriteLine($"{book.Title}, {book.Price}");
}
//with LINQ query Operators:
var cheaperBooks = from b in books
where b.Price < 10
orderby b.Title
select b.Title;
//============
//other LINQ methods
var single = books.Single(b => b.Title == "Book 3"); //if it can't find, it will crash. It wants one and only one object, if you're not sure better to use...
Console.WriteLine(single.Title);
var singleOrDefault = books.SingleOrDefault(b => b.Title == "hmm doesnt exist"); //returns null if it can't find, better to avoid exception crashing
Console.WriteLine(singleOrDefault == null);
var first = books.First(); //gives first book
var firstWithPredicate = books.First(b => b.Title == "Book 4"); //gives first book with that title, i.e. the one with price as $14.
Console.WriteLine(firstWithPredicate.Price);
var firstOrDefault = books.FirstOrDefault(b => b.Title == "Book 08089"); //if nothing matches the lambda condition, it returns null without throwing exception
var last = books.Last();
var lastOrDefault = books.LastOrDefault();
var skip = books.Skip(2).Take(3); //this will skip the first 2, and take the next 3 to the new list.
Console.WriteLine($"Skip:");
foreach (var book in skip)
{
Console.WriteLine(book.Title);
}
var count = books.Count(); //will be 5
var max = books.Max(b => b.Price); //what does max mean? in this case, highest price.
Console.WriteLine(max); //this is the price itself.
var min = books.Min(b => b.Price);
Console.WriteLine(min);
var sum = books.Sum(b => b.Price); //sum based on price of books
Console.WriteLine(sum);
var averagePrice = books.Average(b => b.Price);
Console.WriteLine(averagePrice); //float!
}
static void Main(string[] args)
{
var books = new BookRepository().GetBooks();
// Searches collection for items with specific conditions
var cheapBooks = books.Where(book => book.Price < 10);
foreach (var book in cheapBooks)
{
Console.WriteLine(book.Title + " " + book.Price);
}
// Sorts items in collection
var orderedBooks = books.OrderBy(b => b.Title);
foreach (var book in orderedBooks)
{
Console.WriteLine(book.Title + " " + book.Price);
}
// Selects all items in collection and projects them by type fields
var selectedBooks = books.Select(b => b.Title);
foreach (var book in selectedBooks)
{
Console.WriteLine(book);
}
// C# common convention layout for multiple inline LINQ statements
var booksLinq = books
.Where(book => book.Price < 10) // Searches collection for items with specific conditions
.OrderBy(b => b.Title) // Sorts items in collection
.Select(b => b.Title); // Selects all items in collection and projects them by type fields
// OR LINQ Query Operators
var booksLinqQuery =
from b in books
where b.Price < 10
orderby b.Title
select b.Title;
// Another useful LINQ Extension Methods
var singleBook = books.SingleOrDefault(b => b.Title == "ASP.NET MVC"); // returns single item or default value
Console.WriteLine(singleBook != null ? singleBook.Title : "There is no such book in collection");
var firstBook = books.FirstOrDefault(b => b.Title == "Entity Framework");
Console.WriteLine(firstBook.Title + " " + firstBook.Price);
var lastBook = books.LastOrDefault(b => b.Title == "Entity Framework");
Console.WriteLine(lastBook.Title + " " + lastBook.Price);
var skipBooks = books.Skip(2).Take(3);
foreach (var skipBook in skipBooks)
{
Console.WriteLine(skipBook.Title);
}
Console.WriteLine("Books count: " + books.Count());
Console.WriteLine("Books max price: " + books.Max(b => b.Price));
Console.WriteLine("Books min price: " + books.Min(b => b.Price));
Console.WriteLine("Sum of all books prices: " + books.Sum(b => b.Price));
Console.WriteLine("Average of all books prices: " + books.Average(b => b.Price));
}
