//Definition of LINQ
//Stands for Language Integrated Query
//Capability to query objects
//Usage
//You can query objects in memory (LINQ to objects), Databases (LINQ to Entities), XML (LINQ to XML), ADO.NET Data Sets (LINQ to Data Sets)
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;
//LINQ Extension Methods
books.Where(x => x.Price < 10).ToList().ForEach(y => Console.WriteLine(y.Title));
}
static void Main(string[] args)
{
var books = new BookRepository().GetBooks();
/*
* This can be done in one line using LINQ:
* var cheapBooks = new List<Book>();
*
* foreach(var book in books)
* {
* if(book.Price < 10)
* {
* cheapBooks.Add(book);
* }
* }
*/
// LINQ Extension methods
var cheapBooks = books
.Where(b => b.Price < 10)
.OrderBy(b => b.Price)
.Select(b => b.Title);
// LINQ Query operators
var cheaperBooks = from b in books
where b.Price < 10
orderby b.Title
select b.Title;
foreach (var book in cheapBooks)
{
//Console.WriteLine(book.Title + " " + book.Price);
Console.WriteLine(book);
}
Console.WriteLine();
foreach (var book in cheaperBooks)
{
//Console.WriteLine(book.Title + " " + book.Price);
Console.WriteLine(book);
}
Console.WriteLine();
var book1 = books.SingleOrDefault(b => b.Title == "ASP.NET MVC+");
Console.WriteLine(book1);
var book2 = books.FirstOrDefault(b => b.Title == "C# Advanced Topics");
Console.WriteLine(book2.Title + " " + book2.Price);
var book3 = books.LastOrDefault(b => b.Title == "C# Advanced Topics");
Console.WriteLine(book3.Title + " " + book3.Price);
Console.WriteLine();
var books4 = books.Skip(2).Take(3);
foreach (var book in books4)
{
Console.WriteLine(book.Title);
}
Console.WriteLine();
var count = books.Count();
Console.WriteLine(count);
Console.WriteLine();
var maxPrice = books.Max(b => b.Price);
Console.WriteLine(maxPrice);
Console.WriteLine();
var minPrice = books.Min(b => b.Price);
Console.WriteLine(minPrice);
Console.WriteLine();
var totalPrice = books.Sum(b => b.Price);
Console.WriteLine(totalPrice);
}
static void Main(string[] args)
{
var books = new BookRepository().GetBooks();
// LINQ query operators
// always start with from and end with select
var cheapBooks =
from b in books
where b.Price < 10
orderby b.Title
select b.Title;
foreach (var book in cheapBooks)
{
Console.WriteLine(book);
}
var singleBook = books.SingleOrDefault(b => b.Title == "Book 2"); // if there is no book2 it will return the default which is null
Console.WriteLine("Single book: " + singleBook.Title);
var firstBook = books.FirstOrDefault(b => b.Title == "Book 3");
Console.WriteLine("First book that has title Book 3: " + firstBook.Price); // default is null
var lastBook = books.LastOrDefault(b => b.Title == "Book 3");
Console.WriteLine("Last book that has title Book 3: " + lastBook.Price);
var pages = books.Skip(2).Take(3); // skips the first 2 books and takes the next 3
foreach (var pagedBook in pages)
{
Console.WriteLine(pagedBook.Title);
}
var count = books.Count();
Console.WriteLine("Count: " + count);
var maxPrice = books.Max(b => b.Price); // returns the book with the max price
Console.WriteLine("Max: " + maxPrice);
var sumPrice = books.Sum(b => b.Price);
Console.WriteLine("Total: " + sumPrice);
// 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);*/
// after using select for the title, book is now a string because it returns an
// IEnumerable of just the title of the books. This can no longer be used
/* foreach(var book in cheapBooks)
* Console.WriteLine(book.Title + " " + book.Price);*/
// without LINQ
/* var cheapBooks = new List<Book>();
* foreach(var book in books)
* {
* if (book.Price < 10)
* {
* cheapBooks.Add(book);
* Console.WriteLine(book.Title + " " + book.Price);
* }
* }*/
}
