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IDisposable Interface

Defines a method to release allocated resources.

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

'Declaration
<ComVisibleAttribute(True)> _
Public Interface IDisposable
'Usage
Dim instance As IDisposable

The primary use of this interface is to release unmanaged resources. The garbage collector automatically releases the memory allocated to a managed object when that object is no longer used. However, it is not possible to predict when garbage collection will occur. Furthermore, the garbage collector has no knowledge of unmanaged resources such as window handles, or open files and streams.

Important noteImportant Note:

C++ programmers should read Destructors and Finalizers in Visual C++. In the .NET Framework version, the C++ compiler provides support for implementing deterministic disposal of resources and does not allow direct implementation of the Dispose method.

It is a version-breaking change to add the IDisposable interface to an existing class, because it changes the semantics of the class.

For a detailed discussion about how this interface and the Object.Finalize method are used, see the Garbage Collection and Implementing a Dispose Method topics.

Calling the IDisposable Interface

When calling a class that implements the IDisposable interface, use the try/finally pattern to make sure that unmanaged resources are disposed of even if an exception interrupts your application.

For more information about the try/finally pattern, see Try...Catch...Finally Statement (Visual Basic), try-finally (C# Reference), or The try-finally Statement.

Note that you can use the using statement (Using in Visual Basic) instead of the try/finally pattern. For more information, see the Using Statement (Visual Basic) documentation or the using Statement (C# Reference) documentation. 

The following example demonstrates how to create a resource class that implements the IDisposable interface.

Imports System
Imports System.ComponentModel

' The following example demonstrates how to create 
' a resource class that implements the IDisposable interface 
' and the IDisposable.Dispose method. 
Public Class DisposeExample

   ' A class that implements IDisposable. 
   ' By implementing IDisposable, you are announcing that  
   ' instances of this type allocate scarce resources. 
   Public Class MyResource
      Implements IDisposable
      ' Pointer to an external unmanaged resource. 
      Private handle As IntPtr
      ' Other managed resource this class uses. 
      Private component As component
      ' Track whether Dispose has been called. 
      Private disposed As Boolean = False 

      ' The class constructor. 
      Public Sub New(ByVal handle As IntPtr)
         Me.handle = handle
      End Sub 

      ' Implement IDisposable. 
      ' Do not make this method virtual. 
      ' A derived class should not be able to override this method. 
      Public Overloads Sub Dispose() Implements IDisposable.Dispose
         Dispose(True)
         ' This object will be cleaned up by the Dispose method. 
         ' Therefore, you should call GC.SupressFinalize to 
         ' take this object off the finalization queue  
         ' and prevent finalization code for this object 
         ' from executing a second time.
         GC.SuppressFinalize(Me)
      End Sub 

      ' Dispose(bool disposing) executes in two distinct scenarios. 
      ' If disposing equals true, the method has been called directly 
      ' or indirectly by a user's code. Managed and unmanaged resources 
      ' can be disposed. 
      ' If disposing equals false, the method has been called by the  
      ' runtime from inside the finalizer and you should not reference  
      ' other objects. Only unmanaged resources can be disposed. 
      Private Overloads Sub Dispose(ByVal disposing As Boolean)
         ' Check to see if Dispose has already been called. 
         If Not Me.disposed Then 
            ' If disposing equals true, dispose all managed  
            ' and unmanaged resources. 
            If disposing Then 
               ' Dispose managed resources.
               component.Dispose()
            End If 

            ' Call the appropriate methods to clean up  
            ' unmanaged resources here. 
            ' If disposing is false,  
            ' only the following code is executed.
            CloseHandle(handle)
            handle = IntPtr.Zero

            ' Note disposing has been done.
            disposed = True 

         End If 
      End Sub 

      ' Use interop to call the method necessary   
      ' to clean up the unmanaged resource.
      <System.Runtime.InteropServices.DllImport("Kernel32")> _
      Private Shared Function CloseHandle(ByVal handle As IntPtr) As [Boolean]
      End Function 

      ' This finalizer will run only if the Dispose method  
      ' does not get called. 
      ' It gives your base class the opportunity to finalize. 
      ' Do not provide finalize methods in types derived from this class. 
      Protected Overrides Sub Finalize()
         ' Do not re-create Dispose clean-up code here. 
         ' Calling Dispose(false) is optimal in terms of 
         ' readability and maintainability.
         Dispose(False)
         MyBase.Finalize()
      End Sub 
   End Class 

   Public Shared Sub Main()
      ' Insert code here to create 
      ' and use the MyResource object. 
   End Sub 

End Class

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
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