Join查询可以用一个查询,搜索两个相关数据,用键字段把结果连接起来
示例代码如下:
- 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; }
- }
- class Order
- {
- public string ID { get; set; }
- public decimal Amount { get; set; }
- }
- class Program
- {
- static void Main(string[] args)
- {
- List<Order> orders = new List<Order> {
- new Order { ID="P", Amount=100 },
- new Order { ID="Q", Amount=200 },
- new Order { ID="R", Amount=300 },
- new Order { ID="S", Amount=400 },
- new Order { ID="T", Amount=500 },
- new Order { ID="U", Amount=600 },
- new Order { ID="V", Amount=700 },
- new Order { ID="W", Amount=800 },
- new Order { ID="X", Amount=900 },
- new Order { ID="Y", Amount=1000 },
- new Order { ID="Z", Amount=1100 }
- };
- List<Customer> customers = new List<Customer> {
- new Customer { ID="A", City="New York", Country="USA", Region="North America", Sales=9999},
- new Customer { ID="B", City="Mumbai", Country="India", Region="Asia", Sales=8888},
- new Customer { ID="C", City="Karachi", Country="Pakistan", Region="Asia", Sales=7777},
- new Customer { ID="D", City="Delhi", Country="India", Region="Asia", Sales=6666},
- new Customer { ID="E", City="São Paulo", Country="Brazil", Region="South America", Sales=5555 },
- new Customer { ID="F", City="Moscow", Country="Russia", Region="Europe", Sales=4444 },
- new Customer { ID="G", City="Seoul", Country="Korea", Region="Asia", Sales=3333 },
- new Customer { ID="H", City="Istanbul", Country="Turkey", Region="Asia", Sales=2222 },
- new Customer { ID="I", City="Shanghai", Country="China", Region="Asia", Sales=1111 },
- new Customer { ID="J", City="Lagos", Country="Nigeria", Region="Africa", Sales=1000 },
- new Customer { ID="K", City="Mexico City", Country="Mexico", Region="North America", Sales=2000 },
- new Customer { ID="L", City="Jakarta", Country="Indonesia", Region="Asia", Sales=3000 },
- new Customer { ID="M", City="Tokyo", Country="Japan", Region="Asia", Sales=4000 },
- new Customer { ID="N", City="Los Angeles", Country="USA", Region="North America", Sales=5000 },
- new Customer { ID="O", City="Cairo", Country="Egypt", Region="Africa", Sales=6000 },
- new Customer { ID="P", City="Tehran", Country="Iran", Region="Asia", Sales=7000 },
- new Customer { ID="Q", City="London", Country="UK", Region="Europe", Sales=8000 },
- new Customer { ID="R", City="Beijing", Country="China", Region="Asia", Sales=9000 },
- new Customer { ID="S", City="Bogotá", Country="Colombia", Region="South America", Sales=1001 },
- new Customer { ID="T", City="Lima", Country="Peru", Region="South America", Sales=2002 }
- };
- //Join查询
- var queryResults =
- from c in customers
- join o in orders on c.ID equals o.ID //用join连接两个查询数据
- select new { c.ID, c.City, SalesBefore = c.Sales, NewOrder = o.Amount, SalesAfter = c.Sales + o.Amount };
- foreach (var item in queryResults)
- {
- WriteLine(item);
- }
- }
- }