TransactionIsolationLevel 列舉
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
指定 TransactionAttribute的值。
public enum class TransactionIsolationLevel[System.Serializable]
public enum TransactionIsolationLevel[<System.Serializable>]
type TransactionIsolationLevel = Public Enum TransactionIsolationLevel- 繼承
- 屬性
欄位
| 名稱 | 值 | Description |
|---|---|---|
| Any | 0 | 元件的隔離等級是從呼叫元件的隔離等級中取得的。 若此為根分量，則所用的隔離層級為 Serializable。 |
| ReadUncommitted | 1 | 發放共享鎖，且不承認專屬鎖。 |
| ReadCommitted | 2 | 在讀取資料時會保留共享鎖以避免讀取修改過的資料，但資料可能在交易結束前被更改，導致無法重複讀取或出現虛空資料。 |
| RepeatableRead | 3 | 查詢中使用的所有資料都會被鎖住，防止其他使用者更新資料。 防止不可重複讀取，但幻影列仍可能出現。 |
| Serializable | 4 | 在交易完成前防止更新或插入。 |
範例
以下程式碼範例展示了該 TransactionIsolationLevel 型別的使用。
#using <System.EnterpriseServices.dll>
using namespace System;
using namespace System::EnterpriseServices;
using namespace System::Reflection;
// References:
// System.EnterpriseServices
// An instance of this class will inherit its caller's transaction isolation
// level if available. If not, it will use isolation level Serializable.
[Transaction(Isolation=TransactionIsolationLevel::Any)]
public ref class IsolationAny : public ServicedComponent
{
};
// An instance of this class will read only committed data, but non-repeatable
// reads and phantom rows are still possible.
[Transaction(Isolation=TransactionIsolationLevel::ReadCommitted)]
public ref class IsolationReadCommitted : public ServicedComponent
{
};
// An instance of this class will read committed and uncommitted data, so dirty
// reads, non-repeatable reads, and phantom rows are possible.
[Transaction(Isolation=TransactionIsolationLevel::ReadUncommitted)]
public ref class IsolationReadUncommitted : public ServicedComponent
{
};
// An instance of this class will read only committed data and place shared
// locks on the data, preventing other users from modifying it, but other users
// can still insert rows into the data set, so phantom rows are still possible.
[Transaction(Isolation=TransactionIsolationLevel::RepeatableRead)]
public ref class IsolationRepeatableRead : public ServicedComponent
{
};
// An instance of this class will read only committed data and place a range
// lock on the data set, preventing other users from updating or inserting rows
// into the data set until its transaction is complete.
[Transaction(Isolation=TransactionIsolationLevel::Serializable)]
public ref class IsolationSerializable : public ServicedComponent
{
};
using System;
using System.EnterpriseServices;
using System.Reflection;
// References:
// System.EnterpriseServices
// An instance of this class will inherit its caller's transaction isolation
// level if available. If not, it will use isolation level Serializable.
[Transaction(Isolation=TransactionIsolationLevel.Any)]
public class TransactionAttribute_IsolationAny : ServicedComponent
{
}
// An instance of this class will read only committed data, but non-repeatable
// reads and phantom rows are still possible.
[Transaction(Isolation=TransactionIsolationLevel.ReadCommitted)]
public class TransactionAttribute_IsolationReadCommitted : ServicedComponent
{
}
// An instance of this class will read committed and uncommitted data, so dirty
// reads, non-repeatable reads, and phantom rows are possible.
[Transaction(Isolation=TransactionIsolationLevel.ReadUncommitted)]
public class TransactionAttribute_IsolationReadUncommitted : ServicedComponent
{
}
// An instance of this class will read only committed data and place shared
// locks on the data, preventing other users from modifying it, but other users
// can still insert rows into the data set, so phantom rows are still possible.
[Transaction(Isolation=TransactionIsolationLevel.RepeatableRead)]
public class TransactionAttribute_IsolationRepeatableRead : ServicedComponent
{
}
// An instance of this class will read only committed data and place a range
// lock on the data set, preventing other users from updating or inserting rows
// into the data set until its transaction is complete.
[Transaction(Isolation=TransactionIsolationLevel.Serializable)]
public class TransactionAttribute_IsolationSerializable : ServicedComponent
{
}
Imports System.EnterpriseServices
Imports System.Reflection
' References:
' System.EnterpriseServices
' An instance of this class will inherit its caller's transaction isolation
' level if available. If not, it will use isolation level Serializable.
<Transaction(Isolation := TransactionIsolationLevel.Any)> _
Public Class TransactionAttribute_IsolationAny
Inherits ServicedComponent
End Class
' An instance of this class will read only committed data, but non-repeatable
' reads and phantom rows are still possible.
<Transaction(Isolation := TransactionIsolationLevel.ReadCommitted)> _
Public Class TransactionAttribute_IsolationReadCommitted
Inherits ServicedComponent
End Class
' An instance of this class will read committed and uncommitted data, so dirty
' reads, non-repeatable reads, and phantom rows are possible.
<Transaction(Isolation := TransactionIsolationLevel.ReadUncommitted)> _
Public Class TransactionAttribute_IsolationReadUncommitted
Inherits ServicedComponent
End Class
' An instance of this class will read only committed data and place shared
' locks on the data, preventing other users from modifying it, but other users
' can still insert rows into the data set, so phantom rows are still possible.
<Transaction(Isolation := TransactionIsolationLevel.RepeatableRead)> _
Public Class TransactionAttribute_IsolationRepeatableRead
Inherits ServicedComponent
End Class
' An instance of this class will read only committed data and place a range
' lock on the data set, preventing other users from updating or inserting rows
' into the data set until its transaction is complete.
<Transaction(Isolation := TransactionIsolationLevel.Serializable)> _
Public Class TransactionAttribute_IsolationSerializable
Inherits ServicedComponent
End Class
