LINQ to Object(集运算符与JOIN)

class Order

{

public string ID { get; set; }

public decimal Amount { get; set; }

}

class Customer

{

public string ID { get; set; }

public string City { get; set; }

public string Country { get; set; }

public string Region { get; set; }

public decimal Sales { get; set; }

public override string ToString()

{

return "ID:" + ID + "City:" + City + "Country:" + Country +

"Region:" + Region + "Sales:" + Sales;

}

}

class Program

{

static void Main(string[] args)

{

List<Customer> customers = new List<Customer>{

new Customer{ID = "A",City = "New York", Country = "USA",

Region = "North American", Sales = 999},

new Customer{ID = "B",City = "Mumbai", Country = "India",

Region = "Asia", Sales = 888},

new Customer{ID = "C",City = "Karachi", Country = "Pakistan",

Region = "Asia", Sales = 777},

new Customer{ID = "D",City = "Delhi", Country = "India",

Region = "Asia", Sales = 666},

new Customer{ID = "E",City = "So Paul", Country = "Brazil",

Region = "South America", Sales = 555},

new Customer{ID = "F",City = "Moscow", Country = "Russia",

Region = "Europe", Sales = 444},

new Customer{ID = "G",City = "Seoul", Country = "Korea",

Region = "Asia", Sales = 333},

new Customer{ID = "H",City = "Istanbul", Country = "Turkey",

Region = "Asia", Sales = 222},

new Customer{ID = "I",City = "Shanghai", Country = "China",

Region = "Asia", Sales = 1111},

new Customer{ID = "J",City = "Lagos", Country = "Nigeria",

Region = "Africa", Sales = 1000}};

List<Order> orders = new List<Order>{

new Order{ID="E", Amount = 100},

new Order{ID="F", Amount = 200},

new Order{ID="G", Amount = 300},

new Order{ID="H", Amount = 400},

new Order{ID="I", Amount = 500},

new Order{ID="J", Amount = 600},

new Order{ID="K", Amount = 700},

new Order{ID="L", Amount = 800},

new Order{ID="M", Amount = 900},

new Order{ID="N", Amount = 1000},

new Order{ID="O", Amount = 1100}};

var customerIDs =

from c in customers

select c.ID;

var orderIDs =

from o in orders

select o.ID;

//-----------------------------------------Intersect、Excpt、Union用法 begin----------------------------------------------------

/* var customersWithOrders = customerIDs.Intersect(orderIDs);//两个集合的交集

foreach (var item in customersWithOrders)

{

Console.WriteLine(item);

}

var customersWithOrders = customerIDs.Except(orderIDs);//第一个结果集中有，而第二个结果集中没有的项

foreach (var item in customersWithOrders)

{

Console.WriteLine(item);

}

var customersWithOrders = customerIDs.Union(orderIDs);//两个集合的并集 并删除重复项

foreach (var item in customersWithOrders)

{

Console.Write("{0} ",item);

}*/

//-----------------------------------------Intersect、Excpt、Union用法 end----------------------------------------------------

//-------------------------------------------------join用法 begin----------------------------------------------------

var queryResults =

from c in customers

join o in orders on c.ID equals o.ID

select new { c.ID, c.City, SalesBefore = c.Sales, NewOrder = o.Amount, SalesAfter = c.Sales + o.Amount };

foreach (var item in queryResults)

{

Console.WriteLine(item);

}

//-------------------------------------------------join用法 end----------------------------------------------------

Console.WriteLine();

}

}