IDisposable 介面

定義

提供用於釋放 Unmanaged 資源的機制。

public interface class IDisposable
public interface IDisposable
[System.Runtime.InteropServices.ComVisible(true)]
public interface IDisposable
type IDisposable = interface
[<System.Runtime.InteropServices.ComVisible(true)>]
type IDisposable = interface
Public Interface IDisposable
衍生
屬性

範例

下列範例示範如何建立實作 IDisposable 介面的資源類別。

#using <System.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::ComponentModel;
using namespace System::Windows::Forms;

// The following example demonstrates how to create a class that 
// implements the IDisposable interface and the IDisposable.Dispose
// method with finalization to clean up unmanaged resources. 
//
public ref class MyResource: public IDisposable
{
private:

   // Pointer to an external unmanaged resource.
   IntPtr handle;

   // A managed resource this class uses.
   Component^ component;

   // Track whether Dispose has been called.
   bool disposed;

public:
   // The class constructor.
   MyResource( IntPtr handle, Component^ component )
   {
      this->handle = handle;
      this->component = component;
      disposed = false;
   }

   // This method is called if the user explicitly disposes of the
   // object (by calling the Dispose method in other managed languages, 
   // or the destructor in C++). The compiler emits as a call to 
   // GC::SuppressFinalize( this ) for you, so there is no need to 
   // call it here.
   ~MyResource() 
   {
      // Dispose of managed resources.
      component->~Component();

      // Call C++ finalizer to clean up unmanaged resources.
      this->!MyResource();

      // Mark the class as disposed. This flag allows you to throw an
      // exception if a disposed object is accessed.
      disposed = true;
   }

   // Use interop to call the method necessary to clean up the 
   // unmanaged resource.
   //
   [System::Runtime::InteropServices::DllImport("Kernel32")]
   static Boolean CloseHandle( IntPtr handle );

   // The C++ finalizer destructor ensures that unmanaged resources get
   // released if the user releases the object without explicitly 
   // disposing of it.
   //
   !MyResource()
   {      
      // Call the appropriate methods to clean up unmanaged 
      // resources here. If disposing is false when Dispose(bool,
      // disposing) is called, only the following code is executed.
      CloseHandle( handle );
      handle = IntPtr::Zero;
   }

};

void main()
{
   // Insert code here to create and use the MyResource object.
   MyResource^ mr = gcnew MyResource((IntPtr) 42, (Component^) gcnew Button());
   mr->~MyResource();
}
using System;
using 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 base class that implements IDisposable.
    // By implementing IDisposable, you are announcing that
    // instances of this type allocate scarce resources.
    public class MyResource: IDisposable
    {
        // Pointer to an external unmanaged resource.
        private IntPtr handle;
        // Other managed resource this class uses.
        private Component component = new Component();
        // Track whether Dispose has been called.
        private bool disposed = false;

        // The class constructor.
        public MyResource(IntPtr handle)
        {
            this.handle = handle;
        }

        // Implement IDisposable.
        // Do not make this method virtual.
        // A derived class should not be able to override this method.
        public void Dispose()
        {
            Dispose(disposing: true);
            // This object will be cleaned up by the Dispose method.
            // Therefore, you should call GC.SuppressFinalize to
            // take this object off the finalization queue
            // and prevent finalization code for this object
            // from executing a second time.
            GC.SuppressFinalize(this);
        }

        // 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.
        protected virtual void Dispose(bool disposing)
        {
            // Check to see if Dispose has already been called.
            if(!this.disposed)
            {
                // If disposing equals true, dispose all managed
                // and unmanaged resources.
                if(disposing)
                {
                    // Dispose managed resources.
                    component.Dispose();
                }

                // 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;
            }
        }

        // Use interop to call the method necessary
        // to clean up the unmanaged resource.
        [System.Runtime.InteropServices.DllImport("Kernel32")]
        private extern static Boolean CloseHandle(IntPtr handle);

        // Use C# finalizer syntax for finalization code.
        // 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 finalizer in types derived from this class.
        ~MyResource()
        {
            // Do not re-create Dispose clean-up code here.
            // Calling Dispose(disposing: false) is optimal in terms of
            // readability and maintainability.
            Dispose(disposing: false);
        }
    }
    public static void Main()
    {
        // Insert code here to create
        // and use the MyResource object.
    }
}
// The following example demonstrates how to create
// a resource class that implements the IDisposable interface
// and the IDisposable.Dispose method.
open System
open System.ComponentModel
open System.Runtime.InteropServices

// Use interop to call the method necessary
// to clean up the unmanaged resource.
[<DllImport "Kernel32">]
extern Boolean CloseHandle(nativeint handle)

// A base class that implements IDisposable.
// By implementing IDisposable, you are announcing that
// instances of this type allocate scarce resources.
type MyResource(handle: nativeint) =
    // Pointer to an external unmanaged resource.
    let mutable handle = handle

    // Other managed resource this class uses.
    let comp = new Component()
    
    // Track whether Dispose has been called.
    let mutable disposed = false

    // Implement IDisposable.
    // Do not make this method virtual.
    // A derived class should not be able to override this method.
    interface IDisposable with
        member this.Dispose() =
            this.Dispose true
            // This object will be cleaned up by the Dispose method.
            // Therefore, you should call GC.SuppressFinalize to
            // take this object off the finalization queue
            // and prevent finalization code for this object
            // from executing a second time.
            GC.SuppressFinalize this

    // 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.
    abstract Dispose: bool -> unit
    override _.Dispose(disposing) =
        // Check to see if Dispose has already been called.
        if not disposed then
            // If disposing equals true, dispose all managed
            // and unmanaged resources.
            if disposing then
                // Dispose managed resources.
                comp.Dispose()

            // Call the appropriate methods to clean up
            // unmanaged resources here.
            // If disposing is false,
            // only the following code is executed.
            CloseHandle handle |> ignore
            handle <- IntPtr.Zero

            // Note disposing has been done.
            disposed <- true


    // 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 finalizer in types derived from this class.
    override this.Finalize() =
        // Do not re-create Dispose clean-up code here.
        // Calling Dispose(disposing: false) is optimal in terms of
        // readability and maintainability.
        this.Dispose false
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(disposing:=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.
      Protected Overridable 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(disposing:=False) is optimal in terms of
         ' readability and maintainability.
         Dispose(disposing:=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

備註

此介面的主要用途是釋放非受控資源。 當不再使用該物件時,垃圾收集行程會自動釋放配置給 Managed 物件的記憶體。 不過,無法預測何時會發生垃圾收集。 此外,垃圾收集行程不知道非受控資源,例如視窗控制碼或開啟的檔案和資料流程。

Dispose使用這個介面的 方法,將 Unmanaged 資源與垃圾收集行程一起明確釋放。 當不再需要物件時,物件的取用者可以呼叫這個方法。

警告

這是將介面新增 IDisposable 至現有類別的重大變更。 因為類型預先存在的取用者無法呼叫 Dispose ,所以您無法確定您的類型所持有的非受控資源將會釋放。

IDisposable.Dispose因為不再需要實例所擁有的資源時,類型的取用者會呼叫實作,所以您應該將 Managed 物件包裝在 SafeHandle (建議的替代) 中,或者您應該覆寫 Object.Finalize 以釋放取用者忘記呼叫 Dispose 的 Unmanaged 資源。

重要

在.NET Framework中,C++ 編譯器支援具決定性的資源處置,而且不允許直接實作 Dispose 方法。

如需如何使用這個介面和 Object.Finalize 方法的詳細討論,請參閱 垃圾收集實作 Dispose 方法 主題。

使用實作 IDisposable 的物件

如果您的應用程式只使用實作 IDisposable 介面的物件,您應該在使用完物件時呼叫物件的 IDisposable.Dispose 實作。 根據您的程式設計語言,您可以使用下列兩種方式之一來執行此動作:

  • 使用 C# 和 Visual Basic 中的 語句,以及 use F# 中的 語句或 using 函式等 using 語言建構。

  • 將對 實作的 IDisposable.Dispose 呼叫包裝在 區塊中 try / finally

注意

IDisposable 作的類型檔請注意事實,並包含呼叫其 Dispose 實作的提醒。

C#、F# 和 Visual Basic Using 語句

如果您的語言支援 C# 中的using語句、Visual Basic 中的Using語句或 F# 中的use語句之類的建構,您可以使用它,而不是明確地呼叫 IDisposable.Dispose 自己。 下列範例會使用此方法來定義 WordCount 類別,以保留檔案的相關資訊及其中的字數。

using System;
using System.IO;
using System.Text.RegularExpressions;

public class WordCount
{
    private String filename = String.Empty;
    private int nWords = 0;
    private String pattern = @"\b\w+\b";

    public WordCount(string filename)
    {
        if (!File.Exists(filename))
            throw new FileNotFoundException("The file does not exist.");

        this.filename = filename;
        string txt = String.Empty;
        using (StreamReader sr = new StreamReader(filename))
        {
            txt = sr.ReadToEnd();
        }
        nWords = Regex.Matches(txt, pattern).Count;
    }

    public string FullName
    { get { return filename; } }

    public string Name
    { get { return Path.GetFileName(filename); } }

    public int Count
    { get { return nWords; } }
}
open System.IO
open System.Text.RegularExpressions

type WordCount(filename) =
    let txt = 
        if File.Exists filename |> not then
            raise (FileNotFoundException "The file does not exist.")

        use sr = new StreamReader(filename)
        sr.ReadToEnd()

    let pattern = @"\b\w+\b"
    
    let nWords = Regex.Matches(txt, pattern).Count

    member _.FullName = filename

    member _.Name = Path.GetFileName filename

    member _.Count = nWords
Imports System.IO
Imports System.Text.RegularExpressions

Public Class WordCount
   Private filename As String
   Private nWords As Integer
   Private pattern As String = "\b\w+\b" 

   Public Sub New(filename As String)
      If Not File.Exists(filename) Then
         Throw New FileNotFoundException("The file does not exist.")
      End If   
      
      Me.filename = filename
      Dim txt As String = String.Empty
      Using sr As New StreamReader(filename)
         txt = sr.ReadToEnd()
      End Using
      nWords = Regex.Matches(txt, pattern).Count
   End Sub
   
   Public ReadOnly Property FullName As String
      Get
         Return filename
      End Get   
   End Property
   
   Public ReadOnly Property Name As String
      Get
         Return Path.GetFileName(filename)
      End Get   
   End Property
   
   Public ReadOnly Property Count As Integer
      Get
         Return nWords
      End Get
   End Property
End Class

F using #) 中的語句 (use 運算式實際上是語法便利性。 在編譯時期,語言編譯器會實作 try / finally 區塊的中繼語言 (IL) 。

如需 語句的詳細資訊 using ,請參閱 Using 語句 或使用 語句 主題。

Try/Finally 區塊

如果您的程式設計語言不支援 C# 或 Visual Basic 中的 語句或 F# 中的 語句之類的 using 建構,或者如果您不想使用它,您可以從 語句的 區塊呼叫 IDisposable.Disposefinallyfinally try / 。 use 下列範例會將 using 上一個範例中的 區塊取代為 try / finally 區塊。

using System;
using System.IO;
using System.Text.RegularExpressions;

public class WordCount2
{
    private String filename = String.Empty;
    private int nWords = 0;
    private String pattern = @"\b\w+\b";

    public WordCount2(string filename)
    {
        if (!File.Exists(filename))
            throw new FileNotFoundException("The file does not exist.");

        this.filename = filename;
        string txt = String.Empty;
        StreamReader sr = null;
        try
        {
            sr = new StreamReader(filename);
            txt = sr.ReadToEnd();
        }
        finally
        {
            if (sr != null) sr.Dispose();
        }
        nWords = Regex.Matches(txt, pattern).Count;
    }

    public string FullName
    { get { return filename; } }

    public string Name
    { get { return Path.GetFileName(filename); } }

    public int Count
    { get { return nWords; } }
}
open System.IO
open System.Text.RegularExpressions

type WordCount2(filename) =
    let txt = 
        if File.Exists filename |> not then
            raise (FileNotFoundException "The file does not exist.")

        let sr = new StreamReader(filename)
        try
            sr.ReadToEnd()
        finally
            sr.Dispose()

    let pattern = @"\b\w+\b"
    
    let nWords = Regex.Matches(txt, pattern).Count

    member _.FullName = filename

    member _.Name = Path.GetFileName filename

    member _.Count = nWords
Imports System.IO
Imports System.Text.RegularExpressions

Public Class WordCount2
   Private filename As String
   Private nWords As Integer
   Private pattern As String = "\b\w+\b" 

   Public Sub New(filename As String)
      If Not File.Exists(filename) Then
         Throw New FileNotFoundException("The file does not exist.")
      End If   
      
      Me.filename = filename
      Dim txt As String = String.Empty
      Dim sr As StreamReader = Nothing
      Try
         sr = New StreamReader(filename)
         txt = sr.ReadToEnd()
      Finally
         If sr IsNot Nothing Then sr.Dispose() 
      End Try
      nWords = Regex.Matches(txt, pattern).Count
   End Sub
   
   Public ReadOnly Property FullName As String
      Get
         Return filename
      End Get   
   End Property
   
   Public ReadOnly Property Name As String
      Get
         Return Path.GetFileName(filename)
      End Get   
   End Property
   
   Public ReadOnly Property Count As Integer
      Get
         Return nWords
      End Get
   End Property
End Class

如需模式的詳細資訊 try / finally ,請參閱試用...抓住。。。Finally Statementtry-finallytry...finally Expressiontry-finally 語句

實作 IDisposable

如果您的類型直接使用非受控資源,或想要自行使用可處置的資源,您應該實 IDisposable 作 。 當不再需要實例時,類型的取用者可以呼叫您的 IDisposable.Dispose 實作來釋放資源。 若要處理無法呼叫 Dispose 的情況,您應該使用衍生自 SafeHandle 的類別來包裝 Unmanaged 資源,或者應該覆寫 Object.Finalize 參考型別的 方法。 不論是哪一種情況,您都會使用 Dispose 方法來執行使用 Unmanaged 資源之後所需的任何清除,例如釋放、釋放或重設 Unmanaged 資源。 如需實作 IDisposable.Dispose 的詳細資訊,請參閱 Dispose (bool) 方法多載

重要

如果您要定義使用 Unmanaged 資源的基類,且其具有或可能具有應處置的 Dispose 子類別,您應該實 IDisposable.Dispose 作 方法並提供 的第二個多載,如下一節所述。

IDisposable 和繼承階層

應可處置之子類別的基類必須如下所示實 IDisposable 作。 每當您在Visual Basic) 中未 sealed (NotInheritable 的任何類型上實 IDisposable 作時,都應該使用此模式。

  • 它應該提供一個公用、非虛擬 Dispose() 方法和受保護的虛擬 Dispose(Boolean disposing) 方法。

  • 方法 Dispose() 必須呼叫 Dispose(true) ,而且應該隱藏效能的最終處理。

  • 基底類型不應該包含任何完成項。

下列程式碼片段反映基類的處置模式。 它會假設您的類型不會覆寫 Object.Finalize 方法。

using System;
using System.IO;
using System.Runtime.InteropServices;

class BaseClass1 : IDisposable
{
    // Flag: Has Dispose already been called?
    bool disposed = false;
    // Instantiate a FileStream instance.
    FileStream fs = new FileStream("test.txt", FileMode.OpenOrCreate);

    // Public implementation of Dispose pattern callable by consumers.
    public void Dispose()
    {
        Dispose(disposing: true);
        GC.SuppressFinalize(this);
    }

    // Protected implementation of Dispose pattern.
    protected virtual void Dispose(bool disposing)
    {
        if (disposed)
            return;

        if (disposing)
        {
            fs.Dispose();
            // Free any other managed objects here.
            //
        }

        disposed = true;
    }
}
open System
open System.IO

type BaseClass1() =
    // Flag: Has Dispose already been called?
    let mutable disposed = false

    // Instantiate a FileStream instance.
    let fs = new FileStream("test.txt", FileMode.OpenOrCreate)

    interface IDisposable with
        // Public implementation of Dispose pattern callable by consumers.
        member this.Dispose() =
            this.Dispose true
            GC.SuppressFinalize this

    // Implementation of Dispose pattern.
    abstract Dispose: bool -> unit
    override _.Dispose(disposing) =
        if not disposed then
            if disposing then
                fs.Dispose()
                // Free any other managed objects here.
            disposed <- true
Imports System.IO
Imports System.Runtime.InteropServices

Class BaseClass1 : Implements IDisposable
   ' Flag: Has Dispose already been called?
   Dim disposed As Boolean = False
   ' Instantiate a FileStream instance.
   Dim fs As FileStream = New FileStream("test.txt", FileMode.OpenOrCreate)

   ' Public implementation of Dispose pattern callable by consumers.
   Public Sub Dispose() _
              Implements IDisposable.Dispose
      Dispose(disposing:=True)
      GC.SuppressFinalize(Me)
   End Sub

   ' Protected implementation of Dispose pattern.
   Protected Overridable Sub Dispose(disposing As Boolean)
      If disposed Then Return

      If disposing Then
         fs.Dispose()
         ' Free any other managed objects here.
         '
      End If

      disposed = True
   End Sub
End Class

如果您覆寫 Object.Finalize 方法,您的類別應該實作下列模式。

using System;

class BaseClass2 : IDisposable
{
    // Flag: Has Dispose already been called?
    bool disposed = false;

    // Public implementation of Dispose pattern callable by consumers.
    public void Dispose()
    {
        Dispose(disposing: true);
        GC.SuppressFinalize(this);
    }

    // Protected implementation of Dispose pattern.
    protected virtual void Dispose(bool disposing)
    {
        if (disposed)
            return;

        if (disposing)
        {
            // Free any other managed objects here.
            //
        }

        // Free any unmanaged objects here.
        //
        disposed = true;
    }

    ~BaseClass2()
    {
        Dispose(disposing: false);
    }
}
open System

type BaseClass2() =
    // Flag: Has Dispose already been called?
    let mutable disposed = false

    interface IDisposable with
        // Public implementation of Dispose pattern callable by consumers.
        member this.Dispose() =
            this.Dispose true
            GC.SuppressFinalize this

    // Implementation of Dispose pattern.
    abstract Dispose: bool -> unit
    override _.Dispose(disposing) =
        if not disposed then
            if disposing then
                // Free any other managed objects here.
                ()

            // Free any unmanaged objects here.
            disposed <- true

    override this.Finalize() =
        this.Dispose false
Class BaseClass : Implements IDisposable
   ' Flag: Has Dispose already been called?
   Dim disposed As Boolean = False

   ' Public implementation of Dispose pattern callable by consumers.
   Public Sub Dispose() _
              Implements IDisposable.Dispose
      Dispose(disposing:=True)
      GC.SuppressFinalize(Me)
   End Sub

   ' Protected implementation of Dispose pattern.
   Protected Overridable Sub Dispose(disposing As Boolean)
      If disposed Then Return

      If disposing Then
         ' Free any other managed objects here.
         '
      End If

      ' Free any unmanaged objects here.
      '
      disposed = True
   End Sub

   Protected Overrides Sub Finalize()
      Dispose(disposing:=False)
   End Sub
End Class

子類別應實作可處置模式,如下所示:

  • 它們必須覆寫 Dispose(Boolean) 並呼叫基底類別 Dispose(Boolean) 實作。

  • 如有需要,它們可以提供完成項。 完成項必須呼叫 Dispose(false)

請注意,衍生類別本身不會實 IDisposable 作 介面,而且不包含無 Dispose 參數方法。 它們只會覆寫基類 Dispose(Boolean) 方法。

下列程式碼片段反映衍生類別的處置模式。 它會假設您的類型不會覆寫 Object.Finalize 方法。

using System;
using System.IO;
using System.Runtime.InteropServices;

class MyDerivedClass : MyBaseClass
{
    // Flag: Has Dispose already been called?
    bool disposed = false;
    // Instantiate a FileStream instance.
    FileStream fs = new FileStream("test.txt", FileMode.OpenOrCreate);

    // Protected implementation of Dispose pattern.
    protected override void Dispose(bool disposing)
    {
        if (disposed)
            return;

        if (disposing)
        {
            fs.Dispose();
            // Free any other managed objects here.
            //
        }

        // Free any unmanaged objects here.
        //

        disposed = true;
        // Call base class implementation.
        base.Dispose(disposing);
    }
}
open Microsoft.Win32.SafeHandles
open System

type MyDerivedClass() =
    inherit MyBaseClass()
    
    // Flag: Has Dispose already been called?
    let mutable disposed = false
    // Instantiate a FileStream instance.
    let fs = new FileStream("test.txt", FileMode.OpenOrCreate)

    // Implementation of Dispose pattern.
    override _.Dispose(disposing) =
        if not disposed then
            if disposing then
                fs.Dispose()
                // Free any other managed objects here.

            // Free any unmanaged objects here.
            disposed <- true
            // Call base class implementation.
            base.Dispose disposing
Imports System.IO
Imports System.Runtime.InteropServices

Class DerivedClass2 : Inherits BaseClass2
   ' Flag: Has Dispose already been called?
   Dim disposed As Boolean = False
   ' Instantiate a FileStream instance.
   Dim fs As FileStream = New FileStream("test.txt", FileMode.OpenOrCreate)

   ' Protected implementation of Dispose pattern.
   Protected Overrides Sub Dispose(disposing As Boolean)
      If disposed Then Return

      If disposing Then
         fs.Dispose()
         ' Free any other managed objects here.
         '
      End If

      ' Free any unmanaged objects here.
      '
      disposed = True

      ' Call base class implementation.
      MyBase.Dispose(disposing)
   End Sub
End Class

方法

Dispose()

執行與釋放 (Free)、釋放 (Release) 或重設 Unmanaged 資源相關聯之應用程式定義的工作。

適用於

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