2數(shù)據(jù)查詢與增刪改查操作

EF4.X及以前版 EF EF生成的實(shí)體類都是分部的(partial)，因此，可示例:以下代碼為OrderClient實(shí)體類重寫了publicpublicpartialclassOrderClient {AddressStr=…,ClientName=….,新建對(duì)象時(shí),無需指定主鍵字段ClientID當(dāng)對(duì)象插入DB之后,client對(duì)象的ClientID屬性會(huì)自動(dòng)獲取新值(因?yàn)镺rderClient表的ClientID字 firstClient.AddressStr="modifiedAddress"; 直接刪除對(duì)象- 直接刪除對(duì)象- 更“武斷”的方法，直接向數(shù)據(jù)庫發(fā)送SQL"DELETEFROM……); EF publicpublicenum{Detached=Unchanged=Added=Deleted=Modified=} 在合適的時(shí)機(jī)（見下頁幻燈片），DbContext.ChangeTracker對(duì)象檢查對(duì)象屬性值的更改或 當(dāng)調(diào)用DbContext.SaveChanges()方法保存數(shù)據(jù)它所管理的所有的DbEntityEntry對(duì)象的狀態(tài) {if(client!=null){Console.WriteLine("在修改屬性前："+clientEntry.State);client.AddressStrnewAddress";}} Console.WriteLine("在修改屬性前：狀態(tài)={0}",clientEntry.State);client.AddressStr="newAddress";", {} foreach(vardestinationin{}}varvarquery=fromdincontext.Destinations.AsNoTracking()whered.Country=="Australia" 關(guān)聯(lián)，之后設(shè)置關(guān)聯(lián) RequiredOptional Mastermaster=context.Masters.FirstOrDefault()Mastermaster=context.Masters.FirstOrDefault() 在前面示例程序運(yùn)行過程中，Master對(duì)象的Details屬性實(shí)際上是一publicpublicpartialclass{public{}publicvirtualICollection<Detail>Details{get;set; Mastermaster=context.Masters.FirstOrDefault()Mastermaster=context.Masters.FirstOrDefault()context.Entry(detail).State=EntityState.Deleted; 如果是RequiredDetaildetail=master.Details.ElementAt(0);Detaildetail=master.Details.ElementAt(0); Detaildetail=master.Details.ElementAt(0);context.Entry(detail).State=EntityState.Deleted; Detaildetail=master.Details.ElementAt(0);