01net进阶开发版7个专题08课程代码课件09linq表达式

C#fromwhere根据布尔表达式()selectgroupintojoingroupselectorderbyjoinletusingSystem;usingSystem.Collections.Generic;usingSystem.Linq;usingnamespace{class publicstringID{get;set; publicstringCity{get;set; publicstringCountry{get;set; publicstringRegion{get;set; publicdecimalSales{get;set; publicoverridestringToString()//重写ToString(),默认的ToString()仅 return"ID:"+ID+"City:"+City+"Country:"+Country+"Region:"+Region+"Sales:"+Sales; class publicstringID{get;set; publicdecimalAmount{get;set;class /// /// ///<param /// privatestaticint[] otsofNumbers(int Random Randomgenerator=newRandom(1);//使用指定 值初始化Random int[]result=new for(inti=0;i<count; result[i]= return //1. //1.用var关键 //2.指定数据源：from子 //3.指定条件：where子 //5.完成：使用foreach循 staticvoidMain(string[] //string[]names={"Alono","Zheng","Yuan","Song","Hsieh","Small","She","Sza","Sam","Fa","Iyl" ////varqueryResults=fromnin // where orderbyndescending//ordebyn.Substring(n.Length- selectn;//查询语 varqueryResultsnames.OrderBy(nn).Where(nn.StartsWith("S"));//方法语法Lambda表达式 ////varqueryResults=names.OrderByDescending(n=>=> //foreach(varitemin // //int[]numbers= //varqueryResults=fromnin wheren< select //foreach(varitemin ine(queryResults.Max List<Customer>customers=newList<Customer> newCustomer{ID="A",City="NewYork",Country="NorthAmerica",Sales newCustomer{ID="B",City="NewYork",Country="NorthAmerica",Sales newCustomer{ID="C",City="XiAn",Country ="Asia",Sales newCustomer{ID="D",City="New="USA",Region="NorthAmerica",Sales newCustomer{ID="E",City ",Region="Asia",Sales newCustomer{ID="F",City="New="USA",Region="NorthAmerica",Sales //varqueryReaults fromnin wheren.Region== select //foreach(variteminqueryReaults //投影是在LINQ查询中从其他数据类型中创建 //varqueryResults fromcin wherec.Region== selectnew{c.City,c.Country,c.Sales //varqueryResults=customers.Where(c=>c.Region=="Asia").Select(c=>new{c.City,c.Country,c.Sales}); //varqueryResults=customers.Select(c=>new{c.City,c.Country,c.Sales}).Where(c=>c.City=="XiAn"); //foreach(varitemin varqueryResults1=customers.Select(c=> varqueryResults2=(fromcincustomersselectAnyAny和 boolanyUSA=customers.Any(c=>c.Country== if(anyUSA ine("somecustomersarein boolallAsia=customers.All(c=>c.Region== if(allAsia ine("Allcustomersarein //多级多级排 varqueryReaults3 fromnin wheren.Region== orderbyn.Regionn.Countrydescendingn.City级 select varqueryResults4 customers.OrderBy(c=>c.Region).ThenByDescending(c=>c.Country).ThenBy(c=>c.City).Select(c=>new{c.ID,c.Region,c.Country,c.City}); //方法语法排组合查询（组合查询（group字段是 //要计算每个组的总和，应先生成一个新的结果集 varqueryResults5=fromcin groupcbyc.Regioninto selectnew{TotalSales=cg.Sum(c=>c.Sales),Region=cg.Key}; varorderedResults=fromcgin orderbycg.TotalSales select foreach(varitemin ine(item.TotalSales+"\t:"+ TakeTake //Take从查询结果中提取前n个结 //Skip从查询结果中跳过前n个结果 foreach(variteminorderedResults.Take ine(item.TotalSales+"\t:"+FirstFirst和 () //FirstOrDefault当查询条件不满足是使First()则返回 ine(queryReaults3.FirstOrDefault(n=>n.Region==集运集运算 List<Order>orders=new newOrder newOrder{ID="B",Amount newOrder{ID="H",Amount varcustomersIDs=fromcin select varordersIDs=fromoin select varcustomersWithOrders= foreach(varitemincustomersWithOrders ine(item varordersNoCustomers= foreach(variteminordersNoCustomers ine(item varallCustomersOrders= foreach(varitemin //使用Join运算符在一个查询中查找多个集合中的相关数据，用键字段把结果连接起 varqueryResults9 fromcin joinoinordersonc.IDequals selectnew{c.ID,c.City,SalesBefore=c.Sales,NewOrder=o.Amount,SalesAfter=c.Sales+o.Amount}; foreach(variteminqueryResults9 ine(item }into子句作为一个临时标识符，用于groupselectjoin子句中。它了into子句前LINQ语句中使用。namespace{class staticvoidMain(string[] List<GuestInfo>gList=new new Name Name=" Age=="026*-888888**" new Name Name 漩 Age=="017*- new Name Name 巧 Age=="029*- ///姓"肖""董" varquery=fromguestin letg= whereg肖||g董 select foreach(vargin g.Name,g.Age, }joinjoin子句进行关联//////publicclass /// /// publicstringName{get;set; /// 职 /// publicstringTilte{get;set;class staticvoidMain(string[] List<GuestInfo>gList=new new Name Name=" Age=="026*-888888**" new Name Name 漩 Age=="017*- new Name Name 巧 Age=="029*- new Name Name= Age=="089*- List<GuestTitle>titleList=new newGuestTitle{ newGuestTitle{Name=" ",Tilte="金刀汉王 newGuestTitle{Name=" ",Tilte="天下第一丁 newGuestTitleName 漩Tilte出云公主newGuestTitle{Name=巧Tilte酒店newGuestTitle{Name=巧Tilte乖巧人儿 varquery=fromguestin jointitleintitleListonguest.Nameequals selectnew{Name=guest.Name,Title=title.Tilte,Age=guest.Age}; foreach(vargin ine(string.Format("{0} :{2}",g.Name, ine("\n根 varquery2=fromguestin jointitleintitleListonguest.Nameequalstitle.Nameintotgroup selectnew{Name=guest.Name,Titles=tgroup foreach(vargin foreach(varg2in