TransactionIsolationLevel Enumeração
Definição
Importante
Algumas informações dizem respeito a um produto pré-lançado que pode ser substancialmente modificado antes de ser lançado. A Microsoft não faz garantias, de forma expressa ou implícita, em relação à informação aqui apresentada.
Especifica o valor do TransactionAttribute.
public enum class TransactionIsolationLevel[System.Serializable]
public enum TransactionIsolationLevel[<System.Serializable>]
type TransactionIsolationLevel = Public Enum TransactionIsolationLevel- Herança
- Atributos
Campos
| Name | Valor | Description |
|---|---|---|
| Any | 0 | O nível de isolamento para o componente é obtido a partir do nível de isolamento do componente que chama. Se este for o componente raiz, o nível de isolamento utilizado é Serializable. |
| ReadUncommitted | 1 | São emitidas fechaduras partilhadas e não são respeitadas fechaduras exclusivas. |
| ReadCommitted | 2 | Bloqueios partilhados são mantidos enquanto os dados estão a ser lidos para evitar a leitura de dados modificados, mas os dados podem ser alterados antes do fim da transação, resultando em leituras não repetíveis ou dados fantasma. |
| RepeatableRead | 3 | Bloqueios são colocados em todos os dados usados numa consulta, impedindo outros utilizadores de atualizar os dados. Impede leituras não repetíveis, mas as linhas fantasmas ainda são possíveis. |
| Serializable | 4 | Impede a atualização ou inserção até que a transação esteja completa. |
Exemplos
O seguinte exemplo de código demonstra a utilização do TransactionIsolationLevel tipo.
#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