数据的查询与增删改查操作

EntityEntitySQL是一种非常类似于标准SQL的查询语 LINQto LINQtoEntities可以看成是LINQtoObject的一ObjectObjectServices能执行 通过EntitySQL调用ObjectservicesvarvarqueryString="SELECTVALUEc""FROMSampleEntities.ContactsASc"+"WHEREc.FirstName='Robert'";ObjectQuery<Contact>contacts= 不管是使用EntitySQL还是LINQto 我们可以在应用程序中直接使用 直接执行EntitySQL 与LINQtoEntities UserID={0}",UserID={0}",mand("deletefrom[User] 在实际开发中，也经常使用扩展方法+varvarcontacts=.Where(c=>c.FirstName=="Robert").OrderBy((foo) LINQtoEntities和Entity ADO.NETprovider（比如 ObjectService/EntitySQL或Entity ProjectionsinLINQto varvarcontacts=fromcinwhereselectnew{c.Title,c.FirstName,c.LastName fromfromcinwherec.FirstName==letContactName=new{c.Title,c.LastName,c.FirstName}selectContactName fromcincontext.Contactswherec.FirstName=="Robert"selectnew{c.Title,c.LastName,

“动态装配 对varcontactsvarcontacts=fromcincontext.Contactswherec.FirstName=="Robert"letfoo=newContactName=new{c.Title,c.LastName,c.FirstName},}selectfoo;foreach(varcontactin{varname= ine("{0}{1}{2}:#Addresses{3}",name.Title.Trim(),name.FirstName.Trim(),

varvaraddresses=fromainwherea.CountryRegion=="UK"selectnew{a,a.Contact}; fromainfromainwherea.Contact.AddDate>newSystem.DateTime(2009,1,1)orderbya.Contact.LastNameselectnew{a, fromcinfromcinwherec.Addresses.Any(a=>a.CountryRegion=="UK")selectc;fromcinfromcinselectnew{c.LastName,MaxPC=c.Addresses.Max(a=>

FROM[variableA]INcollectionAJOIN[variableB]INcollection monProperty fromcinfromcinjoinoainonc.ContactIDequalsselectnew{oa.FirstName,oa.LastName,c.Title,oa.Street1,oa.City,oa.StateProvince}; fromcinfromcinselectnew{c.FirstName,c.LastName,StreetsCities=fromainc.Addressesselectnew{a.Street1,a.City}}fromoaincontext.vOfficeAddressesselectfromoaincontext.vOfficeAddressesselectnew{oa.FirstName,a.LastName,Title=(fromcinwherec.ContactID==oa.ContactIDselectc.Title).FirstOrDefault(),oa.Street1,oa.City,} varvarcontacts=fromadd(fromoainwhereoa.StateProvince=="Ontario"selectoa)select... varvaruniverse=fromoaincontext.vOfficeAddresseswhereoa.StateProvince=="Ontario"selectvarquery=fromoainuniverseselectnew{contact=(fromcincontext.Contactswherec.ContactID==oa.ContactIDselectc)};varAddressesWithContacts= fromcincontext.Contactsgroupfromcincontext.Contactsgroupcbyc.Titleintomygroupselectmygroupfromcincontext.Contactsgroupfromcincontext.Contactsgroupcbyc.TitleintoMyGrouporderbyMyGroup.Keyselectnew{MyTitle=MyGroup.Key,MyGroupMax=MyGroup.Max(c=>c.AddDate),Count= varvarcontactGraphs=fromcincontext.Contactsselectnew{c,fromcincontext.Contacts.Include("Addresses")wherec.LastName.StartsWith("J")select //Find//Findvarcontact=IQueryable<Contact>contacts=fromcincontext.Contactswherec.ContactID==1selectContactcontact=varcontact=(fromcincontext.Contactswherec.ContactID==1select 可以使用DbSet.Local查询己在本地的数据，这privatestaticvoid{using(varcontext=new{foreach(vardestinationin{}varcount=Console.WriDestinationsinmemory:{0}",count);}} privatestaticprivatestaticvoid{using(varcontext=new .CollectionChanged+=(sender,args){if(args.NewItems!=null)foreach(Destinationiteminargs.NewItems){ ine("Added:"+item.Name);}}if(args.OldItems!=null)foreach(Destinationiteminargs.OldItems) ine("Removed:"+item.Name);}}}} 延迟加载（Lazy publicclasspublicclass{public{this.Lodgings=new}publicvirtualList<Lodging>Lodgings{get;set;}只有当程序要Destination的Lodgings属性时，才会加载如果没有virtual，则Destination的Lodgings属性为空集合。 Eagervarquery=fromdinvarquery=fromdinwhered.Country=="Australia"select 方式——ExplicitLoading: Explicitprivatestaticvoid{using(varcont