ServiceBehaviorAttribute.InstanceContextMode Property
Definition
Important
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Gets or sets the value that indicates when new service objects are created.
public:
property System::ServiceModel::InstanceContextMode InstanceContextMode { System::ServiceModel::InstanceContextMode get(); void set(System::ServiceModel::InstanceContextMode value); };public System.ServiceModel.InstanceContextMode InstanceContextMode { get; set; }member this.InstanceContextMode : System.ServiceModel.InstanceContextMode with get, setPublic Property InstanceContextMode As InstanceContextModeProperty Value
One of the InstanceContextMode values; the default value is PerSession.
Exceptions
The value is not one of the InstanceContextMode values.
Examples
The following code example demonstrates the ServiceBehaviorAttribute properties. The BehaviorService class uses the ServiceBehaviorAttribute attribute to indicate that:
Implementation methods are invoked on the UI thread.
There is one service object for each session.
The service is single-threaded and does not support reentrant calls.
Furthermore, at the operation level, the OperationBehaviorAttribute values indicate that the TxWork method automatically enlists in flowed transactions or creates a new transaction to do the work, and that the transaction is committed automatically if an unhandled exception does not occur.
using System;
using System.ServiceModel;
using System.Transactions;
namespace Microsoft.WCF.Documentation
{
[ServiceContract(
Namespace="http://microsoft.wcf.documentation",
SessionMode=SessionMode.Required
)]
public interface IBehaviorService
{
[OperationContract]
string TxWork(string message);
}
// Note: To use the TransactionIsolationLevel property, you
// must add a reference to the System.Transactions.dll assembly.
/* The following service implementation:
* -- Processes messages on one thread at a time
* -- Creates one service object per session
* -- Releases the service object when the transaction commits
*/
[ServiceBehavior(
ConcurrencyMode=ConcurrencyMode.Single,
InstanceContextMode=InstanceContextMode.PerSession,
ReleaseServiceInstanceOnTransactionComplete=true
)]
public class BehaviorService : IBehaviorService, IDisposable
{
Guid myID;
public BehaviorService()
{
myID = Guid.NewGuid();
Console.WriteLine(
"Object "
+ myID.ToString()
+ " created.");
}
/*
* The following operation-level behaviors are specified:
* -- The executing transaction is committed when
* the operation completes without an
* unhandled exception
* -- Always executes under a flowed transaction.
*/
[OperationBehavior(
TransactionAutoComplete = true,
TransactionScopeRequired = true
)]
[TransactionFlow(TransactionFlowOption.Mandatory)]
public string TxWork(string message)
{
// Do some transactable work.
Console.WriteLine("TxWork called with: " + message);
// Display transaction information.
TransactionInformation info = Transaction.Current.TransactionInformation;
Console.WriteLine("The distributed tx ID: {0}.", info.DistributedIdentifier);
Console.WriteLine("The tx status: {0}.", info.Status);
return String.Format("Hello. This was object {0}.",myID.ToString()) ;
}
public void Dispose()
{
Console.WriteLine(
"Service "
+ myID.ToString()
+ " is being recycled."
);
}
}
}
Imports System.ServiceModel
Imports System.Transactions
Namespace Microsoft.WCF.Documentation
<ServiceContract(Namespace:="http://microsoft.wcf.documentation", SessionMode:=SessionMode.Required)> _
Public Interface IBehaviorService
<OperationContract> _
Function TxWork(ByVal message As String) As String
End Interface
' Note: To use the TransactionIsolationLevel property, you
' must add a reference to the System.Transactions.dll assembly.
' The following service implementation:
' * -- Processes messages on one thread at a time
' * -- Creates one service object per session
' * -- Releases the service object when the transaction commits
'
<ServiceBehavior(ConcurrencyMode:=ConcurrencyMode.Single, InstanceContextMode:=InstanceContextMode.PerSession, _
ReleaseServiceInstanceOnTransactionComplete:=True)> _
Public Class BehaviorService
Implements IBehaviorService, IDisposable
Private myID As Guid
Public Sub New()
myID = Guid.NewGuid()
Console.WriteLine("Object " & myID.ToString() & " created.")
End Sub
'
' * The following operation-level behaviors are specified:
' * -- The executing transaction is committed when
' * the operation completes without an
' * unhandled exception
' * -- Always executes under a flowed transaction.
'
<OperationBehavior(TransactionAutoComplete:=True, TransactionScopeRequired:=True), TransactionFlow(TransactionFlowOption.Mandatory)> _
Public Function TxWork(ByVal message As String) As String Implements IBehaviorService.TxWork
' Do some transactable work.
Console.WriteLine("TxWork called with: " & message)
' Display transaction information.
Dim info As TransactionInformation = Transaction.Current.TransactionInformation
Console.WriteLine("The distributed tx ID: {0}.", info.DistributedIdentifier)
Console.WriteLine("The tx status: {0}.", info.Status)
Return String.Format("Hello. This was object {0}.", myID.ToString())
End Function
Public Sub Dispose() Implements IDisposable.Dispose
Console.WriteLine("Service " & myID.ToString() & " is being recycled.")
End Sub
End Class
End Namespace
The underlying binding must support flowed transactions for the following code example to execute properly. To support flowed transactions using the WSHttpBinding, for example, set the TransactionFlow property to true in code or in an application configuration file. The following code example shows the configuration file for the preceding sample.
<configuration>
<system.serviceModel>
<services>
<service
name="Microsoft.WCF.Documentation.BehaviorService"
behaviorConfiguration="metadataAndDebugEnabled"
>
<host>
<baseAddresses>
<add baseAddress="http://localhost:8080/SampleService"/>
</baseAddresses>
</host>
<!--
Note:
This example code uses the WSHttpBinding to support transactions using the
WS-AtomicTransactions (WS-AT) protocol. WSHttpBinding is configured to use the
protocol, but the protocol is not enabled on some computers. Use the xws_reg -wsat+
command to enable the WS-AtomicTransactions protocol in the MSDTC service.
-->
<endpoint
contract="Microsoft.WCF.Documentation.IBehaviorService"
binding="wsHttpBinding"
bindingConfiguration="wsHttpBindingWithTXFlow"
address="http://localhost:8080/BehaviorService"
/>
<endpoint
contract="Microsoft.WCF.Documentation.IBehaviorService"
binding="netTcpBinding"
bindingConfiguration="netTcpBindingWithTXFlow"
address="net.tcp://localhost:8081/BehaviorService"
/>
<endpoint
address="mex"
binding="mexHttpBinding"
contract="IMetadataExchange"
/>
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior name="metadataAndDebugEnabled">
<serviceDebug
includeExceptionDetailInFaults="true"
/>
<serviceMetadata
httpGetEnabled="true"
httpGetUrl=""
/>
</behavior>
</serviceBehaviors>
</behaviors>
<!-- binding configuration - configures a WSHttpBinding to require transaction flow -->
<bindings>
<wsHttpBinding>
<binding name="wsHttpBindingWithTXFlow" transactionFlow="true" />
</wsHttpBinding>
<netTcpBinding>
<binding name="netTcpBindingWithTXFlow" transactionFlow="true" />
</netTcpBinding>
</bindings>
</system.serviceModel>
</configuration>
Remarks
Use the InstanceContextMode property to specify when new service objects are created. Because the service object is not directly connected to the communicating channel, the lifetime of the service objects is independent of the lifetime of the channel between a client and the service application. The default value, PerSession, instructs the service application to create a new service object when a new communication session is established between a client and the service application. Subsequent calls in the same session are handled by the same object.
PerSession indicates that each service object handles requests from one client channel.
Note
The InstanceContextMode property interacts with some other settings. For example, if the InstanceContextMode value is set to Single the result is that your service can only process one message at a time unless you also set the ConcurrencyMode value to Multiple. This property also produces behavior in combination with the ServiceContractAttribute.SessionMode property. For details, see Sessions, Instancing, and Concurrency.
For singleton lifetime behavior (for example, if the host application calls the ServiceHost constructor and passes an object to use as the service), the service class must set InstanceContextMode to Single, or an exception is thrown at run time.
