Linq中的高级用法

实体

Commodity：

    class Commodity

    {

        public int Id { get; set; }

        public string Name { get; set; }

        public string Price { get; set; }

        public int Num { get; set; }

 

}

 

Customer：

    class Customer

    {

        public int Id { get; set; }

        public string FirstName { get; set; }

        public string LastName { get; set; }

        public string Sex { get; set; }

        public int Age { get; set; }

    }

 

ShoppingCart:

    class ShoppingCart

    {

        public int CommodityId { get; set; }

        public int CustomerId { get; set; }

        public int Num { get; set; }

    }

初始数据

Customer[] customers = new Customer[]{

        new Customer{Id=000001,FirstName="李",LastName="逍遥",Age=18,Sex="男"},

        new Customer{Id=000002,FirstName="赵",LastName="灵儿",Age=16,Sex="女"},

        new Customer{Id=000003,FirstName="林",LastName="月如",Age=18,Sex="女"},

        new Customer{Id=000004,FirstName="阿",LastName="奴",Age=17,Sex="女"}

    };

 

    Commodity[] commodities = new Commodity[]{

        new Commodity{Id=1,Name="金创药",Price="100",Num=999},

        new Commodity{Id=2,Name="花露水",Price="150",Num=999},

        new Commodity{Id=3,Name="腊肉",Price="55",Num=999},

        new Commodity{Id=4,Name="盐巴",Price="20",Num=999},

        new Commodity{Id=5,Name="黑玉断续膏",Price="1000",Num=100},

        new Commodity{Id=6,Name="九花玉露丸",Price="2000",Num=100}

    };

 

    ShoppingCart[] shoppingCart = new ShoppingCart[]{

        new ShoppingCart{CommodityId=1,CustomerId=000001,Num=100},

        new ShoppingCart{CommodityId=2,CustomerId=000001,Num=100},

        new ShoppingCart{CommodityId=1,CustomerId=000002,Num=50},

        new ShoppingCart{CommodityId=2,CustomerId=000002,Num=100},

        new ShoppingCart{CommodityId=4,CustomerId=000003,Num=20},

        new ShoppingCart{CommodityId=3,CustomerId=000003,Num=23},

        new ShoppingCart{CommodityId=5,CustomerId=000003,Num=1},

        new ShoppingCart{CommodityId=6,CustomerId=000003,Num=2}

    };

分组（为多个字段进行分组）

var data3 = from sp in shoppingCart.AsEnumerable<ShoppingCart>()

                group sp by new { sp.CommodityId, sp.CustomerId }

                                                              into cc

                select new

                {

                    CommodityTypeNum = cc.Count<ShoppingCart>(),

                    CommodityId=cc.Key.CommodityId,

                    CustomerId=cc.Key.CustomerId

 

                };

 

    Console.WriteLine("Three Search is Begin");

    foreach (var tmp in data3)

    {

        Console.WriteLine(tmp.CommodityTypeNum);

    }

    Console.WriteLine("\t\n\t\n");

执行结果：Three Search is Begin11111111 分组（对不同表中的字段进行分组）

var data1 = from customer in customers.AsEnumerable<Customer>()

            join shoppingcart in

                        shoppingCart.AsEnumerable<ShoppingCart>()

                        on customer.Id equals shoppingcart.CustomerId

                join commodity in commodities.AsEnumerable<Commodity>() 

on shoppingcart.CommodityId equals commodity.Id

          group new { customer,shoppingcart,commodity}

 by customer.FirstName+customer.LastName into shopDetails

                select new

                {

                    CustomerName = shopDetails.Key,

                    ItemNum = shopDetails.Count(),

                    Items = from t in shopDetails

                            select new { 

                                CommodityName=t.commodity.Name,

                                CommodityPrice=t.commodity.Price,

                                Num=t.shoppingcart.Num

                            }

                  

                };

 

    foreach (var tmp in data1)

    {

        Console.WriteLine(string.Format("CustomerName:{0},CommodityId:{1}"

, new object[] { tmp.CustomerName, tmp.ItemNum}));

        foreach (var tmp2 in tmp.Items)

        {

           Console.WriteLine(string.Format("\tCommodityName:{0}

,CommodityPrice:{1},Num:{2}", tmp2.CommodityName, tmp2.CommodityPrice

, tmp2.Num));

        }

    }

执行结果：CustomerName:李逍遥,CommodityId:2 CommodityName:金创药,CommodityPrice:100,Num:100 CommodityName:花露水,CommodityPrice:150,Num:100CustomerName:赵灵儿,CommodityId:2 CommodityName:金创药,CommodityPrice:100,Num:50 CommodityName:花露水,CommodityPrice:150,Num:100CustomerName:林月如,CommodityId:4 CommodityName:盐巴,CommodityPrice:20,Num:20 CommodityName:腊肉,CommodityPrice:55,Num:23 CommodityName:黑玉断续膏,CommodityPrice:1000,Num:1 CommodityName:九花玉露丸,CommodityPrice:2000,Num:2 左/右连接

var data2 = from c in customers.AsEnumerable()

                join sc in shoppingCart.AsEnumerable() 

on c.Id equals sc.CustomerId into tmpGroup

//这行代码是右连接的关键

 

                from leftjoindata in tmpGroup

.DefaultIfEmpty(

new ShoppingCart { 

CommodityId = -1,

              CustomerId = -1,

   Num = -1 }

)

                select new

                {

                    CustomerName=c.FirstName+c.LastName,

                    CommodityId=leftjoindata.CommodityId,

                    CommodityNum=leftjoindata.Num

                };

 

    foreach (var tmp in data2)

    {

Console.WriteLine(

string.Format("CustomerName:{0}

,CommodityId:{1}

,CommodityNum:{2}"

, tmp.CustomerName

, tmp.CommodityId

, tmp.CommodityNum));

    }

执行结果：CustomerName:李逍遥,CommodityId:1,CommodityNum:100CustomerName:李逍遥,CommodityId:2,CommodityNum:100CustomerName:赵灵儿,CommodityId:1,CommodityNum:50CustomerName:赵灵儿,CommodityId:2,CommodityNum:100CustomerName:林月如,CommodityId:4,CommodityNum:20CustomerName:林月如,CommodityId:3,CommodityNum:23CustomerName:林月如,CommodityId:5,CommodityNum:1CustomerName:林月如,CommodityId:6,CommodityNum:2CustomerName:阿奴,CommodityId:-1,CommodityNum:-1