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AppDomainUnloadedException Class

The exception that is thrown when an attempt is made to access an unloaded application domain.

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

'Declaration
<SerializableAttribute> _
<ComVisibleAttribute(True)> _
Public Class AppDomainUnloadedException _
	Inherits SystemException
'Usage
Dim instance As AppDomainUnloadedException

In the .NET Framework version 2.0, an AppDomainUnloadedException that is not handled in user code has the following effect:

  • If a thread was started in managed code, it is terminated. The unhandled exception is not allowed to terminate the application.

  • If a task is executing on a ThreadPool thread, it is terminated and the thread is returned to the thread pool. The unhandled exception is not allowed to terminate the application.

  • If a thread started in unmanaged code, such as the main application thread, it is terminated. The unhandled exception is allowed to proceed, and the operating system terminates the application.

AppDomainUnloadedException uses the HRESULT COR_E_APPDOMAINUNLOADED, which has the value 0x80131014.

For a list of initial property values for an instance of AppDomainUnloadedException, see the AppDomainUnloadedException constructors.

This section contains two code examples. The first example demonstrates the effects of an AppDomainUnloadedException on various threads, and the second shows elementary application domain unloading.

Example 1

The following code example defines a TestClass class that can be marshaled across application domain boundaries and an Example class containing a static (Shared in Visual Basic) ThreadProc method. The ThreadProc method creates an application domain, creates a TestClass object in the domain, and calls a method of TestClass that unloads the executing domain, causing an AppDomainUnloadedException.

The TestClass method is executed without exception handling from a ThreadPool thread and from an ordinary thread, demonstrating that the unhandled exception terminates the task or thread but not the application. It is then executed with and without exception handling from the main application thread, demonstrating that it terminates the application if not handled.

Imports System
Imports System.Threading
Imports System.Runtime.InteropServices

Public Class Example

    Public Shared Sub Main() 

        ' 1. Queue ThreadProc as a task for a ThreadPool thread.
        ThreadPool.QueueUserWorkItem(AddressOf ThreadProc, _
            " from a ThreadPool thread")
        Thread.Sleep(1000)

        ' 2. Execute ThreadProc on an ordinary thread. 
        Dim t As New Thread(AddressOf ThreadProc)
        t.Start(" from an ordinary thread")
        t.Join()

        ' 3. Execute ThreadProc on the main thread, with  
        '    exception handling. 
        Try
            ThreadProc(" from the main application thread (handled)")
        Catch adue As AppDomainUnloadedException
            Console.WriteLine("Main thread caught AppDomainUnloadedException: {0}", _
                adue.Message)
        End Try 

        ' 4. Execute ThreadProc on the main thread without 
        '    exception handling.
        ThreadProc(" from the main application thread (unhandled)")

        Console.WriteLine("Main: This message is never displayed.")

    End Sub  

    Private Shared Sub ThreadProc(ByVal state As Object) 
        ' Create an application domain, and create an instance 
        ' of TestClass in the application domain. The first 
        ' parameter of CreateInstanceAndUnwrap is the name of 
        ' this executable. If you compile the example code using 
        ' any name other than "Sample.exe", you must change the 
        ' parameter appropriately. 
        Dim ad As AppDomain = AppDomain.CreateDomain("TestDomain")
        Dim o As Object = ad.CreateInstanceAndUnwrap("Sample", "TestClass")
        Dim tc As TestClass = CType(o, TestClass)

        ' In the new application domain, execute a method that 
        ' unloads the AppDomain. The unhandled exception this 
        ' causes ends the current thread.
        tc.UnloadCurrentDomain(state)

        Console.WriteLine("ThreadProc: This message is never displayed.")

    End Sub 
End Class  

' TestClass derives from MarshalByRefObject, so it can be marshaled 
' across application domain boundaries.  

Public Class TestClass
    Inherits MarshalByRefObject

    Public Sub UnloadCurrentDomain(ByVal state As Object) 
        Console.WriteLine(vbLf & "Unloading the current AppDomain{0}.", state)

        ' Unload the current application domain. This causes 
        ' an AppDomainUnloadedException to be thrown. 
        '
        AppDomain.Unload(AppDomain.CurrentDomain)

    End Sub  
End Class  

' This code example produces output similar to the following: 

'Unloading the current AppDomain from a ThreadPool thread. 

'Unloading the current AppDomain from an ordinary thread. 

'Unloading the current AppDomain from the main application thread (handled). 
'Main thread caught AppDomainUnloadedException: The application domain in which the thread was running has been unloaded. 

'Unloading the current AppDomain from the main application thread (unhandled). 

'Unhandled Exception: System.AppDomainUnloadedException: The application domain in which the thread was running has been unloaded. 
'   at TestClass.UnloadCurrentDomain(Object state) 
'   at Example.ThreadProc(Object state) 
'   at Example.Main() 
' 

Example 2

The following code example creates and unloads an application domain, and demonstrates that an AppDomainUnloadedException is thrown on a subsequent attempt to access the unloaded domain.

Imports System
Imports System.Reflection
Imports System.Security.Policy 'for evidence object

Class ADUnload

   Public Shared Sub Main()

      'Create evidence for the new appdomain. 
      Dim adevidence As Evidence = AppDomain.CurrentDomain.Evidence

      ' Create the new application domain. 
      Dim domain As AppDomain = AppDomain.CreateDomain("MyDomain", adevidence)

      Console.WriteLine(("Host domain: " + AppDomain.CurrentDomain.FriendlyName))
      Console.WriteLine(("child domain: " + domain.FriendlyName))
      ' Unload the application domain.
      AppDomain.Unload(domain)

      Try
         Console.WriteLine()
         ' Note that the following statement creates an exception because the domain no longer exists.
         Console.WriteLine(("child domain: " + domain.FriendlyName))

      Catch e As AppDomainUnloadedException
         Console.WriteLine("The appdomain MyDomain does not exist.")
      End Try 
   End Sub 'Main 
End Class 'ADUnload

System.Object
  System.Exception
    System.SystemException
      System.AppDomainUnloadedException

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

XNA Framework

Supported in: 3.0, 2.0, 1.0

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