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CallContext Class

Provides a set of properties that are carried with the execution code path. This class cannot be inherited.

For a list of all members of this type, see CallContext Members.

System.Object
   System.Runtime.Remoting.Messaging.CallContext

[Visual Basic]
<Serializable>
NotInheritable Public Class CallContext
[C#]
[Serializable]
public sealed class CallContext
[C++]
[Serializable]
public __gc __sealed class CallContext
[JScript]
public
   Serializable
class CallContext

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Remarks

CallContext is a specialized collection object similar to a Thread Local Storage for method calls, and provides data slots that are unique to each logical thread of execution. The slots are not shared across call contexts on other logical threads. Objects can be added to the CallContext as it travels down and back up the execution code path, and examined by various objects along the path.

When a remote method call is made to an object in another AppDomain, the CallContext class generates a LogicalCallContext instance that travels along with the remote call. Only objects that expose the ILogicalThreadAffinative interface and are stored in the CallContext are propagated outside the AppDomain in a LogicalCallContext. Objects that do not support this interface are not transmitted in LogicalCallContext instances with remote method calls.

Note   All methods in CallContext are static and operate on the call context in the current Thread.
Note   This class makes a link demand. A SecurityException is thrown if the immediate caller does not have infrastructure permission. See Link Demands for more information.

Example

[Visual Basic, C#, C++] The following code example demonstrates the use of the CallContext class to transmit Principal and Identity Objects to a remote location for identification. To view the code for the LogicalCallContextData class used in this sample, see the example for the ILogicalThreadAffinative interface. To view the code for the HelloServiceClass class used in this sample, see the example for the GetData method. To view the code for the server class used in this sample, see example for the RegisterActivatedServiceType class.

[Visual Basic] 
Imports System
Imports System.Runtime.Remoting
Imports System.Runtime.Remoting.Channels
Imports System.Runtime.Remoting.Channels.Tcp
Imports System.Runtime.Remoting.Messaging
Imports System.Security.Principal


Public Class ClientClass
      
   Public Shared Sub Main()
      
      Dim ident As New GenericIdentity("Bob")
      Dim prpal As New GenericPrincipal(ident, New String() {"Level1"})
      Dim data As New LogicalCallContextData(prpal)
      
      'Enter data into the CallContext
      CallContext.SetData("test data", data)
      
      
      Console.WriteLine(data.numOfAccesses)
      
      ChannelServices.RegisterChannel(New TcpChannel())
      
      RemotingConfiguration.RegisterActivatedClientType(GetType(HelloServiceClass), "tcp://localhost:8082")
      
      Dim service As New HelloServiceClass()
      
      If service Is Nothing Then
         Console.WriteLine("Could not locate server.")
         Return
      End If
      
      
      ' call remote method
      Console.WriteLine()
      Console.WriteLine("Calling remote object")
      Console.WriteLine(service.HelloMethod("Caveman"))
      Console.WriteLine(service.HelloMethod("Spaceman"))
      Console.WriteLine(service.HelloMethod("Bob"))
      Console.WriteLine("Finished remote object call")
      Console.WriteLine()
      
      'Extract the returned data from the call context
      Dim returnedData As LogicalCallContextData = CType(CallContext.GetData("test data"), LogicalCallContextData)
      
      Console.WriteLine(data.numOfAccesses)
      Console.WriteLine(returnedData.numOfAccesses)

   End Sub 'Main

End Class 'ClientClass

[C#] 
using System;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Tcp;
using System.Runtime.Remoting.Messaging;
using System.Security.Principal;

public class ClientClass {

   public static void Main() {
      
      GenericIdentity ident = new GenericIdentity("Bob");
      GenericPrincipal prpal = new GenericPrincipal(ident, 
                                                    new string[] {"Level1"});
      LogicalCallContextData data = new LogicalCallContextData(prpal);      
      
      //Enter data into the CallContext
      CallContext.SetData("test data", data);

      
      Console.WriteLine(data.numOfAccesses);

      ChannelServices.RegisterChannel(new TcpChannel());

      RemotingConfiguration.RegisterActivatedClientType(typeof(HelloServiceClass),
                                                        "tcp://localhost:8082");

      HelloServiceClass service = new HelloServiceClass();

      if(service == null) {
          Console.WriteLine("Could not locate server.");
          return;
      }


      // call remote method
      Console.WriteLine();
      Console.WriteLine("Calling remote object");
      Console.WriteLine(service.HelloMethod("Caveman"));
      Console.WriteLine(service.HelloMethod("Spaceman"));
      Console.WriteLine(service.HelloMethod("Bob"));
      Console.WriteLine("Finished remote object call");
      Console.WriteLine();

      //Extract the returned data from the call context
      LogicalCallContextData returnedData = 
         (LogicalCallContextData)CallContext.GetData("test data");

      Console.WriteLine(data.numOfAccesses);
      Console.WriteLine(returnedData.numOfAccesses);
   }
}

[C++] 
#using <mscorlib.dll>
#using <system.dll>
#using <system.runtime.remoting.dll>

#using <service.dll>

using namespace System;
using namespace System::Runtime::Remoting;
using namespace System::Runtime::Remoting::Channels;
using namespace System::Runtime::Remoting::Channels::Tcp;
using namespace System::Runtime::Remoting::Messaging;
using namespace System::Security::Principal;

int main() 
{
    GenericIdentity* ident = new GenericIdentity(S"Bob");
    String* id __gc[] = new String* __gc[1];
    id[0] = S"Level1";

    GenericPrincipal* prpal = new GenericPrincipal(ident, id );
    LogicalCallContextData* data = new LogicalCallContextData(prpal);      

    //Enter data into the CallContext
    CallContext::SetData(S"test data", data);

    Console::WriteLine(data->numOfAccesses);

    ChannelServices::RegisterChannel(new TcpChannel());

    RemotingConfiguration::RegisterActivatedClientType(__typeof(HelloServiceClass),
        S"tcp://localhost:8082");

    HelloServiceClass* service = new HelloServiceClass();

    if (service == 0) 
    {
        Console::WriteLine(S"Could not locate server.");
        return 0;
    }

    // call remote method
    Console::WriteLine();
    Console::WriteLine(S"Calling remote Object*");
    Console::WriteLine(service->HelloMethod(S"Caveman"));
    Console::WriteLine(service->HelloMethod(S"Spaceman"));
    Console::WriteLine(service->HelloMethod(S"Bob"));
    Console::WriteLine(S"Finished remote Object* call");
    Console::WriteLine();

    //Extract the returned data from the call context
    LogicalCallContextData* returnedData = 
        static_cast<LogicalCallContextData*>(CallContext::GetData(S"test data"));

    Console::WriteLine(data->numOfAccesses);
    Console::WriteLine(returnedData->numOfAccesses);

    return 0;
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Namespace: System.Runtime.Remoting.Messaging

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

Assembly: Mscorlib (in Mscorlib.dll)

.NET Framework Security: 

See Also

CallContext Members | System.Runtime.Remoting.Messaging Namespace | Header

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