public static void Main(string[] args)
{
var books = new BookRepository().GetBooks();
//var book = books.SingleOrDefault(b => b.Title == "ASP.NET MVC++");
//var book = books.First(b => b.Title == "C# Advanced Topics");
var book = books.FirstOrDefault(b => b.Title == "Bleh");
var bookTwo = books.Last(b => b.Title == "C# Advanced Topics");
var pagedBooks = books.Skip(2).Take(3);
var countBooks = books.Count();
var maxPrice = books.Max(b => b.Price);
var sumBooks = books.Sum(b => b.Price);
//Null because "Bleh" doesn't exist
try
{
Console.WriteLine(book.Price);
}
catch (NullReferenceException)
{
Console.WriteLine("Book is null");
}
Console.WriteLine(bookTwo.Price);
foreach (var pageBook in pagedBooks)
{
Console.WriteLine("\n" + pageBook.Title + "| " + pageBook.Price);
}
Console.WriteLine("\nTotal Books: " + countBooks);
Console.WriteLine("\nMax Price: " + maxPrice);
Console.WriteLine("\nSum Price: " + sumBooks);
}
static void Main(string[] args)
{
var books = new BookRepository().GetBooks();
//LINQ query Operators
var cheapers = from b in books //always the first
where b.Price < 15
orderby b.Title
select b.Title; //always the last
//LINQ extension methods
var cheapBooks = books
.Where(a => a.Price < 15)
.OrderBy(a => a.Title)
.Select(b => b.Title + b.Price);
books.Single(b => b.Title.Equals("Title 3")); //Single() return only and only the one object; if there isn't object like this, app thorws exception
//SingleOrDefault() will return null if there is not equilant object, no exception
books.First(c => c.Title == "Title 1"); //First() returns the fist on the collection that satisfies this condition
// FirstOrDefault() return default value instead of exception
books.Last(d => d.Title == "Title 2"); //Last() or LastOrDefault()
books.Skip(1).Take(2); //skip the first one and take following 2
var count = books.Count(); //number of items in collection
var mostexpensiveBook = books.Max(e => e.Price);
foreach (var b in cheapBooks)
{
Console.WriteLine(b);
}
Console.ReadKey();
}
static void Main(string[] args)
{
var books = new BookRepository().GetBooks();
// LINQ Query Operators
var cheapBooks2 =
from b in books // Defines b as books
where b.Price < 10 // Filters books that are over $10
orderby b.Title // Orders the selection by title
select b.Title; // Converts the object elements to strings (book title)
// LINQ Query Methods (is more powerful, since query uses keywords for methods, and not all of them have one)
var cheapBooks = books
.Where(b => b.Price < 10)
.OrderBy(books => books.Title)
.Select(books => books.Title);
foreach (var cheapBook in cheapBooks)
{
System.Console.WriteLine(cheapBook);
}
// Some more examples of LINQ Extension Methods
var book = books.SingleOrDefault(book => book.Title == "El Principito"); // Unlike Where(), this gets only one object
// There's a Single Method, but that throws an exception if it doesn't find anything
System.Console.WriteLine(book == null); // Returns a book with that title, if not found returns null (default object value)
var firstBook = books.First(); // Gets the first book object
var lastBook = books.Last(); // They can also receive delegates as arguments
var pagedBooks = books.Skip(2).Take(3); // It's gonna skip 2 books and store the following three
var maxPrice = books.Max(b => b.Price); // Returns the max value specified (the price, in this case)
var minPrice = books.Min(b => b.Price); // Returns the min value specified
var sumPrice = books.Sum(b => b.Price); // Returns the sum of all elements (prices)
var averagePrice = books.Average(b => b.Price); // Gets the average given value
}
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();
// this is how you do it without LINQ
// var cheapBooks = new List<Book>();
// foreach (var book in books)
// {
// if (book.Price < 10)
// {
// cheapBooks.Add(book);
// }
// }
// LINQ Query Operators
// equivalent to Extension Methods below
var cheaperBooks = from b in books
where b.Price < 10
orderby b.Title
select b.Title;
// LINQ Extension Methods: can chain methods
// Select used for projections
var cheapBooks = books
.Where(b => b.Price < 10)
.OrderBy(b => b.Title)
.Select(b => b.Title);
foreach (var book in cheapBooks)
{
Console.WriteLine(book);
// Console.WriteLine(book.Title + " " + book.Price);
}
var singleBook = books.Single(b => b.Title == "ASP.NET MVC");
var singleOrDefaultBook = books.SingleOrDefault(b => b.Title == "ASP.NET MVC++");
var firstBook = books.First(b => b.Title == "C# Advanced Topics");
var firstOrDefaultBook = books.FirstOrDefault(b => b.Title == "C# Advanced Topics++");
var lastBook = books.Last(b => b.Title == "C# Advanced Topics");
Console.WriteLine(singleBook.Title);
Console.WriteLine(singleOrDefaultBook == null ? "null" : singleOrDefaultBook.Title);
Console.WriteLine(firstBook.Title + " " + firstBook.Price);
Console.WriteLine(firstOrDefaultBook == null ? "null" : firstOrDefaultBook.Title);
Console.WriteLine(lastBook.Title + " " + lastBook.Price);
Console.WriteLine("Paged Books:");
var pagedBooks = books.Skip(2).Take(3);
foreach (var pagedBook in pagedBooks)
{
Console.WriteLine(pagedBook.Title);
}
var count = books.Count();
Console.WriteLine(count);
var maxPrice = books.Max(b => b.Price);
Console.WriteLine(maxPrice);
var minPrice = books.Min(b => b.Price);
Console.WriteLine(minPrice);
var sumPrice = books.Sum(b => b.Price);
Console.WriteLine(sumPrice);
}
static void Main(string[] args)
{
var books = new BookRepository().GetBooks();
// LINQ Query Operators
// var cheaperBooks =
// from b in books
// where b.Price < 10
// orderby b.Title
// select b.Title;
books.Single(b => b.Title == "ASP.NET MVC"); // one object
books.SingleOrDefault(b => b.Title == "ASP.NET MVC++"); //no books match this condition, function returns null
Console.WriteLine(books == null);
var book = books.First(b => b.Title == "C# Advanced Topics"); // First which match
books.FirstOrDefault(b => b.Title == "C# Advanced Topics"); // null if no books match
books.Last(b => b.Title == "C# Advanced Topics");
books.LastOrDefault(b => b.Title == "C# Advanced Topics"); // null if no books match
var pagedBooks = books.Skip(2).Take(3); // skip 2 object and take 3
foreach (var pagedBook in pagedBooks)
{
Console.WriteLine(pagedBook.Title);
}
var countOfBooks = books.Count();
var maxPrice = books.Max(b => b.Price);
var minPrice = books.Min(b => b.Price);
var totalPrices = books.Sum(b => b.Price);
// books.Where() <- to filter and retun a list of books to match to a given condition
// books.Single() <- to filter and return a one book
// books.SingleOrDefault() <- if don't find book return null
// books.First()
// books.FirstOrDefault()
// books.Last()
// books.LastOrDefault()
// books.Min()
// books.Max()
// books.Count()
// books.Sum()
// books.Average(b => b.Price)
// books.Skip(5).Take(3)
// LINQ Extension Methods
// var cheapBooks = books
// .Where(b => b.Price < 10)
// .OrderBy(b => b.Title)
// .Select(b => b.Title);
// foreach (var book in cheapBooks)
// {
// Console.WriteLine(book);
// }
}
static void Main(string[] args)
{
var books = new BookRepository().GetBooks();
var cheapBooks = new List <Book>();
foreach (var book in books)
{
if (book.Price < 10)
{
cheapBooks.Add(book);
}
}
// ŞİMDİ AYNI FİLTRELEMEYİ LINQ İLE YAPALIM
// LINQ Extension Methods
var cheapBooks1 = books.Where(b => b.Price < 10); // Lambda Expression ve where sorgusu
// orderby kullanalım
var cheapBooks2 = books.OrderBy(b => b.Title);
// ucuca ekleyip, hem fiyata göre filtreleyip, hem Title a gore sıralayalım
var cheapBooks3 = books.Where(b => b.Price < 10).OrderBy(b => b.Title);
// ucuca ekleyip, hem fiyata göre filtreleyip, hem Title a gore sıralayalım. Select ekleyelim.
// select projection veya transformation için kullanılıyormuş
// sadece Title listesi oluştu yani string generic listesi
var cheapBooks4 = books
.Where(b => b.Price < 10)
.OrderBy(b => b.Title)
.Select(b => b.Title);
// (Yukarıdaki şekildeki gibi nokta, altsatırda devam etmeye, LINQ Extension Methods diyoruz.)
// Single ile sadece tek birşey seçebiliriz. Fakat dikkat et, eğer o filtren bulunamazsa, app hata verir önlem de almamışsan
var cheapBooks6 = books.Single(b => b.Title == "ASP.NET MVC");
// O objectin olmaması riski de varsa, SingleOrDefault kullanırız. Alttaki örnekte default olarak null gelir bulunamazsa...
var cheapBooks7 = books.SingleOrDefault(b => b.Title == "ASP.NET MVC++"); // ++ eklediigimiz için bulunamıycak.
// First, aynısından sadece ilkini bulur - bulamazsa hata verir
var cheapBooks8 = books.First(b => b.Title == "C# Advanced Topics");
// FirstOrDefault, ilki, ama hiç bulamazsa default olarak bu örnekte null
var cheapBooks9 = books.FirstOrDefault(b => b.Title == "C# Advanced Topics");
// Last, aynısından sadece sonuncuyu bulur - bulamazsa hata verir
var cheapBooks10 = books.Last(b => b.Title == "C# Advanced Topics");
// LastOrDefault, sonuncusu, ama hiç bulamazsa default olarak bu örnekte null
var cheapBooks11 = books.LastOrDefault(b => b.Title == "C# Advanced Topics");
// Skip() ve Take() - ilk 2 tanesini atla, sonra 3 tanesini al
var cheapBooks12 = books.Skip(2).Take(3);
// SQL deki gibi Aggregate Func da var. mesela Count()
var bookCount = books.Count();
// SQL deki Max() - tabi price a göre max olmasını biz söylüycez - float type a return ediyor, çünkü class Books ta, Price type float
var highestPrice = books.Max(b => b.Price); // type: float
// Min()
var minPrice = books.Min(b => b.Price); // type: float
// Sum() - tüm kitapların fiyatı toplamı
var totalPrice = books.Sum(b => b.Price); // type: float
// Average() - tüm kitapların ortalama fiyatı
var avgPrice = books.Average(b => b.Price); // type: float
foreach (var book in cheapBooks)
{
Console.WriteLine(book.Title + " " + book.Price);
}
foreach (var book in cheapBooks4)
{
Console.WriteLine(book);
}
foreach (var book in cheapBooks12)
{
Console.WriteLine(book.Title + " " + book.Price);
}
// LINQ Query Methods
var cheapBooks5 = from b in books
where b.Price < 10
orderby b.Title
select b.Title;
}
static void Main(string[] args)
{
var books = new BookRepository().GetBooks();
Console.WriteLine("number of books:");
var count = books.Count();
Console.WriteLine(count);
Console.WriteLine("name of books:");
foreach (var b in books)
{
Console.WriteLine("Title: " + b);
}
var cheapBooks = books
.Where(b => b.Price < 10)
.OrderBy(b => b.Title)
.Select(b => b.Title);
Console.WriteLine("Cheapbooks:");
foreach (var b in cheapBooks)
{
Console.WriteLine("Title: " + b);
}
Console.WriteLine("favourite book:");
var book = books.Single(b => b.Title == "Solid Mechanics");
Console.WriteLine(book.Title);
Console.WriteLine("first book in collection:");
var firstBook = books.First();
Console.WriteLine("Title: " + firstBook.Title + ". Price: " + firstBook.Price);
Console.WriteLine("last book in collection:");
var lastBook = books.Last();
Console.WriteLine("Title: " + lastBook.Title + ". Price: " + lastBook.Price);
Console.WriteLine("books after skipping first three:");
var remainingBooks = books.Skip(2).Take(2);
foreach (var b in remainingBooks)
{
Console.WriteLine(b.Title);
}
Console.WriteLine("max price: ");
var maxPrice = books.Max(b => b.Price);
Console.WriteLine(maxPrice);
Console.WriteLine("min price: ");
var minPrice = books.Min(b => b.Price);
Console.WriteLine(minPrice);
Console.WriteLine("total price: ");
var totalPrice = books.Sum(b => b.Price);
Console.WriteLine(totalPrice);
}
