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ADO.NET Entity Framework(3)ObjectContext

編輯：關於.NET

1　　說明　　1

2　　Context操作數據　　1

2.1　　AddObject 添加實體　　1

2.2　　DeleteObject 刪除實體　　1

2.3　　Detach 分離實體　　2

2.4　　修改實體　　2

2.5　　ApplyPropertyChanges 修改實體　　2

2.6　　Attach / AttachTo 附加實體　　2

2.7　　CreateEntityKey 創建EntityKey　　3

2.7.1　　EntityKey　　3

2.8　　GetObjectByKey/TryGetObjectByKey 通過EntityKey得到實體　　3

2.9　　CreateQuery 創建查詢　　4

3　　狀態管理　　4

3.1　　EntityState 狀態枚舉　　4

3.2　　Context.ObjectStateManager 管理記錄的狀態　　4

3.2.1　　GetObjectStateEntry 得到狀態實體　　4

3.2.2　　TryGetObjectStateEntry 得到狀態實體　　4

3.2.3　　GetObjectStateEntries 得到狀態實體集合　　5

3.2.4　　ObjectStateManagerChanged 事件　　5

3.3　　ObjectStateEntry 對象　　5

3.3.1　　基本屬性　　5

3.3.2　　State 狀態屬性　　6

3.3.3　　CurrentValues 當前值　　6

3.3.4　　OriginalValues 原始值　　6

3.3.5　　GetModifiedProperties 得到被修改的屬性　　6

3.3.6　　SetModified,SetModifiedProperty 標記為修改　　7

3.3.7　　Delete 標記為刪除　　7

3.3.8　　AcceptChanges 方法　　7

4　　保存修改到數據庫　　8

4.1　　Context.SaveChanges 方法　　8

4.2　　Context.SavingChanges 事件　　9

4.3　　Context.AcceptAllChanges 方法　　9

5　　連接屬性　　9

5.1　　Context.DefaultContainerName 屬性　　9

5.2　　Context.Connection 屬性　　9

5.3　　Context.CommandTimeout 屬性　　10

6　　Context.MetadataWorkspace　　10

7　　數據刷新與並發　　10

7.1　　緩存數據不會自動更新　　10

7.2　　[並發模式]值為[Fixed]的並發異常　　11

7.3　　ObjectContext.Refresh()　　11

7.3.1　　StoreWins　　11

7.3.2　　ClientWins　　12

7.4　　也可以先Refresh()再SaveChanges(),而不用異常捕獲　　13

8　　事務處理　　13

8.1　　同一SubmitChanges 會做默認的事務處理　　13

8.2　　不同SubmitChanges 不會做事務處理　　13

8.3　　System.Data.Common.DbTransaction　　13

8.4　　死鎖(兩個Context使用DbTransaction)　　14

8.5　　TransactionScope 事務(兩個Context)　　14

說明

ObjectContext提供了管理數據的功能

Context操作數據 AddObject 添加實體

將實體添加到集合中,

創建實體時,狀態為EntityState.Detached

當調用AddObject將實體添加到Context時,狀態為EntityState.Added

myContext context = new myContext(); myTab r = new myTab(); r.ID = 10; r.a = "wxwinter"; Console.WriteLine(r.EntityState); //print:Detached context.AddTomyTab(r); Console.WriteLine(r.EntityState); //print:Added context.SaveChanges(); myContext context = new myContext(); myTab newrow = new myTab() { a = "wxd", b = "lzm", c = "wxwinter" }; context.AddObject("myTab",newrow); context.SaveChanges();

DeleteObject 刪除實體

將集合中的實體添標記為刪除

當調用Context.DeleteObject時,並不是將實體移除集合,而是將實體添標記為EntityState.Deleted

myContext context = new myContext(); myTab r = context.myTab.First(p=>p.ID==1); Console.WriteLine(r.EntityState); //print:Unchanged context.DeleteObject(r); Console.WriteLine(r.EntityState); //print:Deleted context.SaveChanges();

Detach 分離實體

將實體從Context中移除,將狀態標記為EntityState.Detached

myContext context = new myContext(); myTab r = myTab.CreatemyTab(22); Console.WriteLine(r.EntityState); //print:Detached context.AddTomyTab(r); Console.WriteLine(r.EntityState); //print:Added context.Detach(r); Console.WriteLine(r.EntityState); //print: Detached

修改實體

可以直接修在實體對象上修改

當修改在Context中的實體時,會將實體的狀態標記為EntityState.Modified

myContext context = new myContext(); myTab r = context.myTab.First(p=>p.ID==1); Console.WriteLine(r.EntityState); //print:Unchanged r.a = "wxwinter"; Console.WriteLine(r.EntityState); //print:Modified context.SaveChanges();

ApplyPropertyChanges 修改實體

使用ApplyPropertyChanges,可以使用不在集合中的實體覆蓋到集合中主鍵對應用實體上

如果內存中沒有主鍵對應的記錄,會報錯

myContext context = new myContext(); myTab r1 = context.myTab.First(p => p.ID == 1); myTab nr = myTab.CreatemyTab(1); nr.a = "wxwinter"; Console.WriteLine(nr.EntityState); //print:Detached Console.WriteLine(r1.EntityState); //print:Unchanged context.ApplyPropertyChanges("myTab", nr); myTab r2 = context.myTab.First(p => p.ID == 1); Console.WriteLine(nr.EntityState); //print:Detached Console.WriteLine(r2.EntityState); //print:Modified context.SaveChanges();

Attach / AttachTo 附加實體

使用Attach方法可將[外部實體]附加到Context集合中

在使用服務器/客戶端模式,或要將[實體]從Context集合中分離,修改後要用Context更新回數據庫時,可用這種方式

Attach與ApplyPropertyChanges有類似之處,都是將Context集合外的[實體]與Context集合內的[實體]同步.

ApplyPropertyChanges調用時,要求對應的[實體]在內存中,Attach不要求

pplyPropertyChanges調用後,集合內的實體狀態會標記為EntityState.Modified

Attach調用後不會修改合內的實體狀態,如要SaveChanges(),要手動標記EntityState.Modified

ApplyPropertyChanges是用[外部實體]全覆蓋Context集合中的[實體],

Attach方式,通過SetModifiedProperty()方法,可在調用SaveChanges()時,只修改只定有字段值

myContext context = new myContext(); myTab v = myTab.CreatemyTab(1); v.EntityKey = context.CreateEntityKey("myTab", v); v.a = "wxwinter"; context.Attach(v); //context.AttachTo("myTab", v); ObjectStateEntry ose = context.ObjectStateManager.GetObjectStateEntry(v); ose.SetModified(); ose.SetModifiedProperty("a"); context.SaveChanges();

修改前

修改後

CreateEntityKey 創建EntityKey

myContext context = new myContext(); myTab nr = myTab.CreatemyTab(1); EntityKey ek= context.CreateEntityKey("myTab", nr);

EntityKey

EntityContainerName 屬性 EntityKeyValues 集合 EntitySetName 屬性 IsTemporary 屬性 GetEntitySet(System.Data.Metadata.Edm.MetadataWorkspace) 方法 OnDeserialized(System.Runtime.Serialization.StreamingContext) 方法 OnDeserializing(System.Runtime.Serialization.StreamingContext) 方法

GetObjectByKey/TryGetObjectByKey 通過EntityKey得到實體

myContext context = new myContext(); myTab nr = myTab.CreatemyTab(1); EntityKey ek= context.CreateEntityKey("myTab", nr); myTab r = context.GetObjectByKey(ek) as myTab ; Console.WriteLine("{0},{1},{2},{3}", r.ID, r.a, r.b, r.c); myContext context = new myContext(); myTab nr = myTab.CreatemyTab(1); EntityKey ek= context.CreateEntityKey("myTab", nr); object obj; if (context.TryGetObjectByKey(ek,out obj)) { myTab r = obj as myTab; Console.WriteLine("{0},{1},{2},{3}", r.ID, r.a, r.b, r.c); }

CreateQuery 創建查詢

更多見esql

myContext context = new myContext(); string esql = "SELECT VALUE DBItemList FROM myContext.DBItemList"; // ObjectQuery<DBItemList> query = new ObjectQuery<DBItemList>(esql, context); ObjectQuery<DBItemList> query = context.CreateQuery<DBItemList>(esql); foreach (DBItemList r in query) { Console.WriteLine(r.NameID); }

狀態管理 EntityState 狀態枚舉

EntityState.Added 已通過AddObject方法加到集合中，AcceptChanges 尚未調用。

EntityState.Deleted 已通過 DeleteObject 方法被刪除。

EntityState.Detached 已被創建，但不屬於任何集合。在以下情況下立即處於此狀態：創建之後添加到集合中之前；或從集合中移除之後。

EntityState.Modified 已被修改，AcceptChanges 尚未調用。

EntityState.Unchanged 自上次調用 AcceptChanges 以來尚未更改

Context.ObjectStateManager 管理記錄的狀態 GetObjectStateEntry 得到狀態實體

ObjectStateEntry = GetObjectStateEntry(實體對像/EntityKey)

得到所指定的[實體對像]或EntityKey的 ObjectStateEntry

myContext context = new myContext(); myTab r = myTab.CreatemyTab(22); context.AddTomyTab(r); // ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r); ObjectStateEntry ose = context.ObjectStateManager.GetObjectStateEntry(r.EntityKey); Console.WriteLine(ose.State); //print:Added

TryGetObjectStateEntry 得到狀態實體

bool = TryGetObjectStateEntry(實體對像/EntityKey,out ObjectStateEntry)

得到所指定的[實體對像]或EntityKey的 ObjectStateEntry

myContext context = new myContext(); myTab r = myTab.CreatemyTab(22); context.AddTomyTab(r); ObjectStateEntry ose; if( context.ObjectStateManager.TryGetObjectStateEntry(r,out ose)) { Console.WriteLine(ose.State); //print:Added }

GetObjectStateEntries 得到狀態實體集合

IEnumerable<ObjectStateEntry> = GetObjectStateEntries(EntityState枚舉)

返回IEnumerable<ObjectStateEntry>,得到EntityState枚舉所指定的某種狀態的列表

myContext context = new myContext(); myTab r = myTab.CreatemyTab(22); context.AddTomyTab(r); IEnumerable<ObjectStateEntry> oseList = context.ObjectStateManager.GetObjectStateEntries(EntityState.Added); foreach (ObjectStateEntry v in oseList) { Console.WriteLine("{0},{1},{2}", v.State, v.CurrentValues["ID"], v.EntitySet.Name); } //print:Added,22,myTab

ObjectStateManagerChanged 事件

CollectionChangeEventHandler(object sender, CollectionChangeEventArgs e) e.Action : 集合操作行為 System.ComponentModel.CollectionChangeAction.Add System.ComponentModel.CollectionChangeAction.Refresh System.ComponentModel.CollectionChangeAction.Remove e.Element : 操作的實體對象 void ObjectStateManager_ObjectStateManagerChanged(object sender, CollectionChangeEventArgs e) { Console.WriteLine(e.Action); myTab v = e.Element as myTab; Console.WriteLine("{0}",v.ID); } //=================================== myContext context = new myContext(); context.ObjectStateManager.ObjectStateManagerChanged+=new CollectionChangeEventHandler(ObjectStateManager_ObjectStateManagerChanged); myTab r = myTab.CreatemyTab(22); context.AddTomyTab(r); /* *print: Add 22 */

ObjectStateEntry 對象基本屬性

IsRelationship 屬性

Entity 屬性

EntityKey 屬性

EntitySet 屬性

State 狀態屬性

EntityState 枚舉

myContext context = new myContext(); myTab r = myTab.CreatemyTab(22); context.AddTomyTab(r); ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r); Console.WriteLine(ose.State); //print:Added

CurrentValues 當前值

處於 deleted 或 detached 狀態的對象沒有當前值。

myContext context = new myContext(); myTab r = new myTab() { ID = 22, a = "wxwinter" }; context.AddTomyTab(r); ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r); Console.WriteLine("{0},{1}",ose.CurrentValues["ID"],ose.CurrentValues["a"]); //print: 22,wxwinter

OriginalValues 原始值

處於 added 或 detached 狀態的對象沒有原始值

myContext context = new myContext(); myTab r = context.myTab.First(p => p.ID == 1); r.a = "wxwinter"; ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r); Console.WriteLine(ose.State); Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]); Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]); /* * print: Modified CurrentValues :1,wxwinter OriginalValues:1,aa */

GetModifiedProperties 得到被修改的屬性

返回IEnumerable<string>

得到被修改的屬性集合

myContext context = new myContext(); myTab r = context.myTab.First(p => p.ID == 1); r.a = "wxwinter"; r.b = "wxd"; ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r); IEnumerable<string> list = ose.GetModifiedProperties(); foreach (string pr in list) { Console.WriteLine(pr); } /* * print: a b */

SetModified,SetModifiedProperty 標記為修改

SetModified() 方法將記錄標記為 EntityState.Modified

只是這樣,調用Context.SaveChanges方法是無法保存修改到數據庫中的,Context.SaveChanges方法要查找被修改過的屬性,

可用SetModifiedProperty方法標記被修改過的屬性

myContext context = new myContext(); myTab r = context.myTab.First(p => p.ID == 1); r.a = "wxwinter"; ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r); ose.AcceptChanges(); Console.WriteLine(ose.State); Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]); Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]); /* * print: Unchanged CurrentValues :1,wxwinter OriginalValues:1,wxwinter */ ose.SetModified(); ose.SetModifiedProperty("a"); Console.WriteLine(ose.State); Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]); Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]); /* * print: Modified CurrentValues :1,wxwinter OriginalValues:1,wxwinter */ context.SaveChanges();

Delete 標記為刪除

標記為EntityState.Deleted

myContext context = new myContext(); myTab r = context.myTab.First(p => p.ID == 1); ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r); ose.Delete(); Console.WriteLine(ose.State); //print: Detached Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]); //print:OriginalValues:1,wxwinter

用 context.DeleteObject方法的效果與上例一樣

myContext context = new myContext(); myTab r = context.myTab.First(p => p.ID == 1); ObjectStateEntry ose = context.ObjectStateManager.GetObjectStateEntry(r); context.DeleteObject(r); Console.WriteLine(ose.State); //print: Detached Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]); //print:OriginalValues:1,wxwinter

AcceptChanges 方法

將記錄的狀態置為EntityState.Unchanged

用[CurrentValues 當前值]替換[OriginalValues 原始值],

使用[ Context.AcceptAllChanges 方法]也有同樣效果

注意:狀態為[EntityState.Deleted ]的記錄,會被[Detach]

myContext context = new myContext(); myTab r = context.myTab.First(p => p.ID == 1); r.a = "wxwinter"; context.AcceptAllChanges(); ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r); ose.AcceptChanges(); Console.WriteLine(ose.State); Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]); Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]); /* * print: Unchanged CurrentValues :1,wxwinter OriginalValues:1,wxwinter */ 當調用AcceptChanges時,如果對像處於[EntityState.Deleted ],會將對象移除集合,這時對像的狀態為[EntityState.Detached ] myContext context = new myContext(); myTab r = context.myTab.First(p => p.ID == 1); ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r); ose.Delete(); ose.AcceptChanges(); Console.WriteLine(ose.State); //print: Detached

保存修改到數據庫 Context.SaveChanges 方法

如果集合中有狀態為EntityState.Added的記錄,用[CurrentValues 當前值]添加到數據庫中

如果集合中有狀態為EntityState.Deleted的記錄,從數據庫是刪除與之對應的數據庫記錄

如果集合中有狀態為EntityState.Modified的記錄,用[OriginalValues 原始值]與對應的數據庫記錄比效,查看並發, 用[CurrentValues 當前值]更新與之對應的數據庫記錄

SaveChanges(true) 將數據保存到數據庫後
將所有記錄狀態標記為EntityState.Unchanged ,(調用Context.AcceptAllChanges ) myContext context = new myContext();
myTab r = context.myTab.First(p => p.ID == 1);

r.a = "wxwinter";
ObjectStateEntry ose = context.ObjectStateManager.GetObjectStateEntry(r);

context.SaveChanges(true);

Console.WriteLine(ose.State);
Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]);
Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]);

/*
* print:
Unchanged
CurrentValues :1,wxwinter
OriginalValues:1,wxwinter
*/ SaveChanges() 與SaveChanges(true)相同 SaveChanges(false) 將數據保存到數據庫,
但並不改變記錄狀態 myContext context = new myContext();
myTab r = context.myTab.First(p => p.ID == 1);

r.a = "wxwinter";
ObjectStateEntry ose = context.ObjectStateManager.GetObjectStateEntry(r);

context.SaveChanges(false);

Console.WriteLine(ose.State);
Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]);
Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]);

/*
* print:
Modified
CurrentValues :1,wxwinter
OriginalValues:1,aa
*/

Context.SavingChanges 事件

myContext context = new myContext(); context.SavingChanges+=new EventHandler(context_SavingChanges); myTab r = context.myTab.First(p => p.ID == 1); r.a = "wxwinter"; context.SaveChanges(); void context_SavingChanges(object sender, EventArgs e) { myContext context = sender as myContext; Console.WriteLine(context.DefaultContainerName); }

Context.AcceptAllChanges 方法

將所有記錄的狀態置為EntityState.Unchanged

用[CurrentValues 當前值]替換[OriginalValues 原始值]

效果與對所在記錄的ObjectStateEntry上調用AcceptAllChanges一樣

注意:狀態為[EntityState.Deleted ]的記錄,會被[Detach]

myContext context = new myContext(); myTab r = context.myTab.First(p => p.ID == 1); r.a = "wxwinter"; context.AcceptAllChanges(); ObjectStateEntry ose= context.ObjectStateManager.GetObjectStateEntry(r); Console.WriteLine(ose.State); Console.WriteLine("CurrentValues :{0},{1}", ose.CurrentValues["ID"], ose.CurrentValues["a"]); Console.WriteLine("OriginalValues:{0},{1}", ose.OriginalValues["ID"], ose.OriginalValues["a"]); /* * print: Unchanged CurrentValues :1,wxwinter OriginalValues:1,wxwinter */

連接屬性 Context.DefaultContainerName 屬性 Context.Connection 屬性 Context.CommandTimeout 屬性 Context.MetadataWorkspace 數據刷新與並發

EF提供了兩種並發沖突處理方式：放任不管方式和開放式並發。默認采用放任不管的方式處理。

如果要使用開放式並發，必須設置相應屬性上的[並發模式]值[Fixed]

後修改數據的ObjectContext緩存了舊版本的數據時,當提交修改後系統就會拋出"OptimisticConcurrencyException"（開放式並發異常）。

當程序捕獲到異常以後，可以使用ObjectContext的Refresh方法對異常采取處理。

緩存數據不會自動更新

公共 myContext context1 = new myContext();
myContext context2 = new myContext(); 查詢 foreach (var r in context1.DBItem)
{
Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);
}

Console.WriteLine("---------------------");

foreach (var r in context2.DBItem)
{
Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);
} a,this is a
b,this is b
c,this is c
---------------------
a,this is a
b,this is b
c,this is c 修改 DBItem dbitem1 = context1.DBItem.First(p => p.ItemID == "a");
dbitem1.ItemMatter = "hello";
context1.SaveChanges(); 再查詢 foreach (var r in context1.DBItem)
{
Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);
}

Console.WriteLine("---------------------");

foreach (var r in context2.DBItem)
{
Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);
} a,hello
b,this is b
c,this is c
---------------------
a,this is a
b,this is b
c,this is c

[並發模式]值為[Fixed]的並發異常

注意,只有後修改數據的ObjectContext緩存了舊版本的數據時,長會產生異常

DBItem dbitem1 = context1.DBItem.First(p => p.ItemID == "a"); dbitem1.ItemMatter = "hello"; context1.SaveChanges(); DBItem dbitem2 = context2.DBItem.First(p => p.ItemID == "a"); dbitem2.ItemMatter = "wxwinter"; context2.SaveChanges();

ObjectContext.Refresh()

Refresh的第一個參數RefreshMode枚舉,RefreshMode.StoreWins,RefreshMode.ClientWins

StoreWins

StoreWins : Refresh以後，用數據庫的值回寫,當前的修改值被放棄

公共 myContext context1 = new myContext();
myContext context2 = new myContext(); 查詢 foreach (var r in context1.DBItem)
{
Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);
}

Console.WriteLine("---------------------");

foreach (var r in context2.DBItem)
{
Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);
} a,this is a
b,this is b
c,this is c
---------------------
a,this is a
b,this is b
c,this is c 修改 DBItem dbitem1 = context1.DBItem.First(p => p.ItemID == "a");
dbitem1.ItemMatter = "hello";
context1.SaveChanges();

DBItem dbitem2 = context2.DBItem.First(p => p.ItemID == "a");

dbitem2.ItemMatter = "wxwinter";
try
{
context2.SaveChanges();
}
catch
{
context2.Refresh( RefreshMode.StoreWins , dbitem2);
} 在System.Data.OptimisticConcurrencyException 中第一次偶然出現的"System.Data.Entity.dll"類型的異常再查詢 foreach (var r in context1.DBItem)
{
Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);
}

Console.WriteLine("---------------------");

foreach (var r in context2.DBItem)
{
Console.WriteLine("{0},{1}", r.ItemID, r.ItemMatter);
} a,hello
b,this is b
c,this is c
---------------------
a,hello
b,this is b
c,this is c

ClientWins

StoreWins: Refresh以後，當前的修改值仍存在,只是告訴ObjectContext知到的並發問題了,這時再調用 ObjectContext.SaveChanges()時,ObjectContext就不會報[開放式並發異常]

也可以先Refresh()再SaveChanges(),而不用異常捕獲

事務處理同一SubmitChanges 會做默認的事務處理

下例由於ItemID主鍵沖突,兩條數據都不會被插入

myContext context1 = new myContext(); DBItem item1 = new DBItem(); item1.ItemID = "w"; item1.ItemMatter = "wxwinter"; context1.AddObject("DBItem", item1); DBItem item2 = new DBItem(); item2.ItemID = "w"; item2.ItemMatter = "wxd"; context1.AddObject("DBItem", item2); context1.SaveChanges();

不同SubmitChanges 不會做事務處理

下例由於ItemID主鍵沖突,後一條數據都不會被插入

myContext context1 = new myContext(); DBItem item1 = new DBItem(); item1.ItemID = "w"; item1.ItemMatter = "wxwinter"; context1.AddObject("DBItem", item1); context1.SaveChanges(); myContext context2 = new myContext(); DBItem item2 = new DBItem(); item2.ItemID = "w"; item2.ItemMatter = "wxd"; context2.AddObject("DBItem", item2); context2.SaveChanges();

System.Data.Common.DbTransaction

下例由於ItemID主鍵沖突,兩條數據都不會被插入

myContext context1 = new myContext(); DBItem item1 = new DBItem(); item1.ItemID = "w"; item1.ItemMatter = "wxwinter"; context1.AddObject("DBItem", item1); if (context1.Connection.State != ConnectionState.Open) { context1.Connection.Open(); } System.Data.Common.DbTransaction tran = context1.Connection.BeginTransaction(); context1.SaveChanges(); try { DBItem item2 = new DBItem(); item2.ItemID = "w"; item2.ItemMatter = "wxd"; context1.AddObject("DBItem", item2); context1.SaveChanges(); tran.Commit(); } catch { tran.Rollback(); }

死鎖(兩個Context使用DbTransaction)

myContext context1 = new myContext(); DBItem item1 = new DBItem(); item1.ItemID = "w"; item1.ItemMatter = "wxwinter"; context1.AddObject("DBItem", item1); if (context1.Connection.State != ConnectionState.Open) { context1.Connection.Open(); } System.Data.Common.DbTransaction tran = context1.Connection.BeginTransaction(); context1.SaveChanges(); try { myContext context2 = new myContext(); DBItem item2 = new DBItem(); item2.ItemID = "w"; item2.ItemMatter = "wxd"; context2.AddObject("DBItem", item2); context2.SaveChanges(); tran.Commit(); } catch { tran.Rollback(); }

TransactionScope 事務(兩個Context)

System.Transactions.TransactionScope

可解決[死鎖(兩個Context使用DbTransaction)]

下例由於ItemID主鍵沖突,兩條數據都不會被插入

using (System.Transactions.TransactionScope tc = new TransactionScope()) { try { myContext context1 = new myContext(); DBItem item1 = new DBItem(); item1.ItemID = "w"; item1.ItemMatter = "wxwinter"; context1.AddObject("DBItem", item1); context1.SaveChanges(); myContext context2 = new myContext(); DBItem item2 = new DBItem(); item2.ItemID = "w"; item2.ItemMatter = "wxd"; context2.AddObject("DBItem", item2); context2.SaveChanges(); tc.Complete(); } catch { } }