C # LINQ & XML

LINQ (language-integrated Query) is a language pattern used as a lookup, Access database, or XML file.

Is the way to communicate object-oriented languages and databases. very similar to SQL.

usingSystem;usingSystem.Collections.Generic;usingSystem.Linq;//LINQ namespacenamespaceprogramming_csharp{//Simple Customer Class     Public classCustomer//Define a Customer object that forms the collection to search    {         Public stringFirstName {Get;Set; }  Public stringLastName {Get;Set; }  Public stringEmailAddress {Get;Set; } //Overrides the object.tostring () to provide a//string representation of the object properties.         Public Override stringToString () {return string. Format ("{0} {1}\nemail: {2}", FirstName, LastName, EmailAddress); }    }

//Create a customer list with sample dataPrivate  StaticList<customer>createcustomerlist () {List<Customer> customers =NewList<customer>   {      NewCustomer {FirstName ="Orlando ", LastName ="Gee",EmailAddress ="[email protected]"},      NewCustomer {FirstName ="Keith ", LastName ="Harris",EmailAddress ="[email protected]" },      NewCustomer {FirstName ="Donna ", LastName ="Carreras",EmailAddress ="[email protected]" },      NewCustomer {FirstName ="Janet ", LastName ="Gates",EmailAddress ="[email protected]" },      NewCustomer {FirstName ="Lucy ", LastName ="Harrington",EmailAddress ="[email protected]" }    }; returncustomers; }

An in-memory collection that makes up the customer

   Static voidMain ()//Main Program{List<Customer> customers =createcustomerlist (); //Find Customer by First nameienumerable<customer> result = fromCustomerinchCustomerswhereCustomer. FirstName = ="Donna"        SelectCustomer//Select on the lastConsole.WriteLine ("FirstName = = \ "Donna\""); foreach(Customer Customerinchresult) {Console.WriteLine (Customer.  ToString ());} //Show Resultscustomers[3]. FirstName ="Donna";//Modifying DataConsole.WriteLine ("FirstName = = \ "Donna\" ( take both)");//Show Results      foreach(Customer Customerinchresult) {Console.WriteLine (Customer.    ToString ());} }  }}//namespace

Join keyword

Connect two data tables connected by the HYPHEN keyword

[Data source 1] Join [data source 2] on [join condition]

LINQ contains Keywords

Where from select and so on

A Where expression filter condition similar to SQL

From indicates the specified range

Select indicates lookup mappings

var keyword

The var universal data type must be initialized

var 1234 ; var " 1234 " ; var New Class1;

C # LINQ & XML