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MarshalByRefObject Class

Enables access to objects across application domain boundaries in applications that support remoting.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public MustInherit Class MarshalByRefObject
Dim instance As MarshalByRefObject

An application domain is a partition in an operating system process where one or more applications reside. Objects in the same application domain communicate directly. Objects in different application domains communicate either by transporting copies of objects across application domain boundaries, or by using a proxy to exchange messages.

MarshalByRefObject is the base class for objects that communicate across application domain boundaries by exchanging messages using a proxy. Objects that do not inherit from MarshalByRefObject are implicitly marshal by value. When a remote application references a marshal by value object, a copy of the object is passed across application domain boundaries.

MarshalByRefObject objects are accessed directly within the boundaries of the local application domain. The first time an application in a remote application domain accesses a MarshalByRefObject, a proxy is passed to the remote application. Subsequent calls on the proxy are marshaled back to the object residing in the local application domain.

Types must inherit from MarshalByRefObject when the type is used across application domain boundaries, and the state of the object must not be copied because the members of the object are not usable outside the application domain where they were created.

This section contains two code examples. The first code example shows how to create an instance of a class in another application domain. The second code example shows a simple class that can be used for remoting.

Example 1

The following code example shows the simplest way to execute code in another application domain. The example defines a class named Worker that inherits MarshalByRefObject, with a method that displays the name of the application domain in which it is executing. The example creates instances of Worker in the default application domain and in a new application domain.


The assembly that contains Worker must be loaded into both application domains, but it could load other assemblies that would exist only in the new application domain.

Imports System
Imports System.Reflection

Public Class Worker
    Inherits MarshalByRefObject

    Public Sub PrintDomain() 
        Console.WriteLine("Object is executing in AppDomain ""{0}""", _
    End Sub  
End Class  

Class Example

    Public Shared Sub Main() 

        ' Create an ordinary instance in the current AppDomain 
        Dim localWorker As New Worker()

        ' Create a new application domain, create an instance 
        ' of Worker in the application domain, and execute code 
        ' there. 
        Dim ad As AppDomain = AppDomain.CreateDomain("New domain")
        Dim remoteWorker As Worker = CType( _
            ad.CreateInstanceAndUnwrap( _
                [Assembly].GetExecutingAssembly().FullName, _
                "Worker"), _

    End Sub  
End Class  

' This code produces output similar to the following: 

'Object is executing in AppDomain "source.exe" 
'Object is executing in AppDomain "New domain"

Example 2

The following example demonstrates a class derived from MarshalByRefObject that is used later in remoting.

Imports System.Runtime.Remoting
Imports System.Security.Permissions

Public Class SetObjectUriForMarshalTest

    Class TestClass
        Inherits MarshalByRefObject
    End Class

    <SecurityPermission(SecurityAction.Demand, Flags:= SecurityPermissionFlag.RemotingConfiguration )> _
    Public Shared Sub Main()
        Dim obj As TestClass = New TestClass()

        RemotingServices.SetObjectUriForMarshal(obj, "testUri")

    End Sub 

End Class


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

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0