다음을 통해 공유


GC.KeepAlive(Object) 메서드

정의

지정된 개체를 참조하여 현재 루틴이 시작된 지점에서 이 메서드가 호출된 지점까지 가비지 컬렉션이 불가능하도록 합니다.

public:
 static void KeepAlive(System::Object ^ obj);
public static void KeepAlive (object obj);
public static void KeepAlive (object? obj);
static member KeepAlive : obj -> unit
Public Shared Sub KeepAlive (obj As Object)

매개 변수

obj
Object

참조할 개체입니다.

예제

다음 코드 예제에서는 메서드의 시작 부분에 개체를 Main 만들고 메서드가 호출될 때까지 KeepAlive 개체를 다시 참조하지 않습니다. 개체는 메서드 및 메서드 호출에도 불구하고 Collect WaitForPendingFinalizers 메서드의 Main 30초 동안 유지됩니다.

using namespace System;
using namespace System::Threading;
using namespace System::Runtime::InteropServices;

// A simple class that exposes two static Win32 functions.
// One is a delegate type and the other is an enumerated type.
public ref class MyWin32
{
public:

   // An enumerated type for the control messages sent to the handler routine.
   enum class CtrlTypes
   {
      CTRL_C_EVENT = 0,
      CTRL_BREAK_EVENT, CTRL_CLOSE_EVENT, CTRL_LOGOFF_EVENT = 5,
      CTRL_SHUTDOWN_EVENT
   };

   delegate Boolean HandlerRoutine(    // A delegate type to be used as the Handler Routine for SetConsoleCtrlHandler.
   CtrlTypes CtrlType );

   // Declare the SetConsoleCtrlHandler function as external and receiving a delegate.

   [DllImport("Kernel32")]
   static Boolean SetConsoleCtrlHandler( HandlerRoutine^ Handler, Boolean Add );
};

public ref class MyApp
{
private:

   // A private static handler function in the MyApp class.
   static Boolean Handler( MyWin32::CtrlTypes CtrlType )
   {
      String^ message = "This message should never be seen!";
      
      // A switch to handle the event type.
      switch ( CtrlType )
      {
         case MyWin32::CtrlTypes::CTRL_C_EVENT:
            message = "A CTRL_C_EVENT was raised by the user.";
            break;

         case MyWin32::CtrlTypes::CTRL_BREAK_EVENT:
            message = "A CTRL_BREAK_EVENT was raised by the user.";
            break;

         case MyWin32::CtrlTypes::CTRL_CLOSE_EVENT:
            message = "A CTRL_CLOSE_EVENT was raised by the user.";
            break;

         case MyWin32::CtrlTypes::CTRL_LOGOFF_EVENT:
            message = "A CTRL_LOGOFF_EVENT was raised by the user.";
            break;

         case MyWin32::CtrlTypes::CTRL_SHUTDOWN_EVENT:
            message = "A CTRL_SHUTDOWN_EVENT was raised by the user.";
            break;
      }
      
      // Use interop to display a message for the type of event.
      Console::WriteLine( message );
      return true;
   }


public:
   static void Test()
   {
      
      // Use interop to set a console control handler.
      MyWin32::HandlerRoutine^ hr = gcnew MyWin32::HandlerRoutine( Handler );
      MyWin32::SetConsoleCtrlHandler( hr, true );
      
      // Give the user some time to raise a few events.
      Console::WriteLine( "Waiting 30 seconds for console ctrl events..." );
      
      // The Object hr is not referred to again.
      // The garbage collector can detect that the object has no
      // more managed references and might clean it up here while
      // the unmanaged SetConsoleCtrlHandler method is still using it.
      // Force a garbage collection to demonstrate how the hr
      // object will be handled.
      GC::Collect();
      GC::WaitForPendingFinalizers();
      GC::Collect();
      Thread::Sleep( 30000 );
      
      // Display a message to the console when the unmanaged method
      // has finished its work.
      Console::WriteLine( "Finished!" );
      
      // Call GC::KeepAlive(hr) at this point to maintain a reference to hr.
      // This will prevent the garbage collector from collecting the
      // object during the execution of the SetConsoleCtrlHandler method.
      GC::KeepAlive( hr );
   }

};

int main()
{
   MyApp::Test();
}
using System;
using System.Threading;
using System.Runtime.InteropServices;

// A simple class that exposes two static Win32 functions.
// One is a delegate type and the other is an enumerated type.
public class MyWin32
{
    // Declare the SetConsoleCtrlHandler function
    // as external and receiving a delegate.
    [DllImport("Kernel32")]
    public static extern Boolean SetConsoleCtrlHandler(HandlerRoutine Handler,
        Boolean Add);

    // A delegate type to be used as the handler routine
    // for SetConsoleCtrlHandler.
    public delegate Boolean HandlerRoutine(CtrlTypes CtrlType);

    // An enumerated type for the control messages
    // sent to the handler routine.
    public enum CtrlTypes
    {
        CTRL_C_EVENT = 0,
        CTRL_BREAK_EVENT,
        CTRL_CLOSE_EVENT,
        CTRL_LOGOFF_EVENT = 5,
        CTRL_SHUTDOWN_EVENT
    }
}

public class MyApp
{
    // A private static handler function in the MyApp class.
    static Boolean Handler(MyWin32.CtrlTypes CtrlType)
    {
        String message = "This message should never be seen!";

        // A switch to handle the event type.
        switch(CtrlType)
        {
            case MyWin32.CtrlTypes.CTRL_C_EVENT:
                message = "A CTRL_C_EVENT was raised by the user.";
                break;
            case MyWin32.CtrlTypes.CTRL_BREAK_EVENT:
                message = "A CTRL_BREAK_EVENT was raised by the user.";
                break;
            case MyWin32.CtrlTypes.CTRL_CLOSE_EVENT:
                message = "A CTRL_CLOSE_EVENT was raised by the user.";
                break;
            case MyWin32.CtrlTypes.CTRL_LOGOFF_EVENT:
                message = "A CTRL_LOGOFF_EVENT was raised by the user.";
                break;
            case MyWin32.CtrlTypes.CTRL_SHUTDOWN_EVENT:
                message = "A CTRL_SHUTDOWN_EVENT was raised by the user.";
                break;
        }

        // Use interop to display a message for the type of event.
        Console.WriteLine(message);

        return true;
    }

    public static void Main()
    {

        // Use interop to set a console control handler.
        MyWin32.HandlerRoutine hr = new MyWin32.HandlerRoutine(Handler);
        MyWin32.SetConsoleCtrlHandler(hr, true);

        // Give the user some time to raise a few events.
        Console.WriteLine("Waiting 30 seconds for console ctrl events...");

        // The object hr is not referred to again.
        // The garbage collector can detect that the object has no
        // more managed references and might clean it up here while
        // the unmanaged SetConsoleCtrlHandler method is still using it.
        
        // Force a garbage collection to demonstrate how the hr
        // object will be handled.
        GC.Collect();
        GC.WaitForPendingFinalizers();
        GC.Collect();
        
        Thread.Sleep(30000);

        // Display a message to the console when the unmanaged method
        // has finished its work.
        Console.WriteLine("Finished!");

        // Call GC.KeepAlive(hr) at this point to maintain a reference to hr.
        // This will prevent the garbage collector from collecting the
        // object during the execution of the SetConsoleCtrlHandler method.
        GC.KeepAlive(hr);
        Console.Read();
    }
}
open System
open System.Threading
open System.Runtime.InteropServices

// A simple module that exposes two static Win32 functions.
// One is a delegate type and the other is an enumerated type.
module MyWin32 =
    // An enumerated type for the control messages
    // sent to the handler routine.
    type CtrlTypes =
        | CTRL_C_EVENT = 0
        | CTRL_BREAK_EVENT = 1
        | CTRL_CLOSE_EVENT = 2
        | CTRL_LOGOFF_EVENT = 5
        | CTRL_SHUTDOWN_EVENT = 6

    // A delegate type to be used as the handler routine for SetConsoleCtrlHandler.
    type HandlerRoutine = delegate of CtrlTypes -> bool

    // Declare the SetConsoleCtrlHandler function
    // as external and receiving a delegate.
    [<DllImport "Kernel32">]
    extern bool SetConsoleCtrlHandler(HandlerRoutine Handler, bool Add)

// A private static handler function in the MyApp class.
let handler (ctrlType: MyWin32.CtrlTypes) =
    let message =
        // Pattern match to handle the event type.
        match ctrlType with
        | MyWin32.CtrlTypes.CTRL_C_EVENT ->
            "A CTRL_C_EVENT was raised by the user."
        | MyWin32.CtrlTypes.CTRL_BREAK_EVENT ->
            "A CTRL_BREAK_EVENT was raised by the user."
        | MyWin32.CtrlTypes.CTRL_CLOSE_EVENT ->
            "A CTRL_CLOSE_EVENT was raised by the user."
        | MyWin32.CtrlTypes.CTRL_LOGOFF_EVENT ->
            "A CTRL_LOGOFF_EVENT was raised by the user."
        | MyWin32.CtrlTypes.CTRL_SHUTDOWN_EVENT ->
            "A CTRL_SHUTDOWN_EVENT was raised by the user."
        | _ -> "This message should never be seen!"

    // Use interop to display a message for the type of event.
    printfn $"{message}"
    true

// Use interop to set a console control handler.
let hr = MyWin32.HandlerRoutine handler
MyWin32.SetConsoleCtrlHandler(hr, true) |> ignore

// Give the user some time to raise a few events.
printfn "Waiting 30 seconds for console ctrl events..."

// The object hr is not referred to again.
// The garbage collector can detect that the object has no
// more managed references and might clean it up here while
// the unmanaged SetConsoleCtrlHandler method is still using it.

// Force a garbage collection to demonstrate how the hr
// object will be handled.
GC.Collect()
GC.WaitForPendingFinalizers()
GC.Collect()

Thread.Sleep 30000

// Display a message to the console when the unmanaged method
// has finished its work.
printfn "Finished!"

// Call GC.KeepAlive(hr) at this point to maintain a reference to hr.
// This will prevent the garbage collector from collecting the
// object during the execution of the SetConsoleCtrlHandler method.
GC.KeepAlive hr
Console.Read() |> ignore
Imports System.Threading
Imports System.Runtime.InteropServices

' A simple class that exposes two static Win32 functions.
' One is a delegate type and the other is an enumerated type.

Public Class MyWin32

   ' Declare the SetConsoleCtrlHandler function as external 
   ' and receiving a delegate.   
   <DllImport("Kernel32")> _
   Public Shared Function SetConsoleCtrlHandler(ByVal Handler As HandlerRoutine, _
         ByVal Add As Boolean) As Boolean
   End Function


   ' A delegate type to be used as the handler routine 
   ' for SetConsoleCtrlHandler.
   Delegate Function HandlerRoutine(ByVal CtrlType As CtrlTypes) As [Boolean]

   ' An enumerated type for the control messages 
   ' sent to the handler routine.

   Public Enum CtrlTypes
      CTRL_C_EVENT = 0
      CTRL_BREAK_EVENT
      CTRL_CLOSE_EVENT
      CTRL_LOGOFF_EVENT = 5
      CTRL_SHUTDOWN_EVENT
   End Enum
End Class

Public Class MyApp

   ' A private static handler function in the MyApp class.
   Shared Function Handler(ByVal CtrlType As MyWin32.CtrlTypes) As [Boolean]
      Dim message As [String] = "This message should never be seen!"

      ' A select case to handle the event type.
      Select Case CtrlType
         Case MyWin32.CtrlTypes.CTRL_C_EVENT
            message = "A CTRL_C_EVENT was raised by the user."
         Case MyWin32.CtrlTypes.CTRL_BREAK_EVENT
            message = "A CTRL_BREAK_EVENT was raised by the user."
         Case MyWin32.CtrlTypes.CTRL_CLOSE_EVENT
            message = "A CTRL_CLOSE_EVENT was raised by the user."
         Case MyWin32.CtrlTypes.CTRL_LOGOFF_EVENT
            message = "A CTRL_LOGOFF_EVENT was raised by the user."
         Case MyWin32.CtrlTypes.CTRL_SHUTDOWN_EVENT
            message = "A CTRL_SHUTDOWN_EVENT was raised by the user."
      End Select

      ' Use interop to display a message for the type of event.
      Console.WriteLine(message)

      Return True
   End Function


   Public Shared Sub Main()
      ' Use interop to set a console control handler.
      Dim hr As New MyWin32.HandlerRoutine(AddressOf Handler)
      MyWin32.SetConsoleCtrlHandler(hr, True)

      ' Give the user some time to raise a few events.
      Console.WriteLine("Waiting 30 seconds for console ctrl events...")

      ' The object hr is not referred to again.
      ' The garbage collector can detect that the object has no
      ' more managed references and might clean it up here while
      ' the unmanaged SetConsoleCtrlHandler method is still using it.      
      ' Force a garbage collection to demonstrate how the hr
      ' object will be handled.
      GC.Collect()
      GC.WaitForPendingFinalizers()
      GC.Collect()

      Thread.Sleep(30000)

      ' Display a message to the console when the unmanaged method
      ' has finished its work.
      Console.WriteLine("Finished!")

      ' Call GC.KeepAlive(hr) at this point to maintain a reference to hr. 
      ' This will prevent the garbage collector from collecting the 
      ' object during the execution of the SetConsoleCtrlHandler method.
      GC.KeepAlive(hr)
      Console.Read()
   End Sub
End Class

설명

이 메서드의 KeepAlive 목적은 가비지 수집기에서 조기에 회수될 위험이 있는 개체에 대한 참조가 있는지 확인하는 것입니다. 이 문제가 발생할 수 있는 일반적인 시나리오는 관리 코드 또는 데이터에 개체에 대한 참조가 없지만 개체가 여전히 관리되지 않는 코드(예: Windows API, 관리되지 않는 DLL 또는 COM을 사용하는 메서드)에서 사용 중인 경우입니다.

이 메서드는 매개 변수를 obj 참조하여 해당 개체가 이 메서드가 호출되는 실행 순서대로 루틴의 시작부터 지점까지 가비지 수집에 부적격하게 만듭니다. 사용 가능한 명령 범위의 시작이 아닌 끝에 이 메서드를 코딩합니다 obj .

이 메서드는 KeepAlive 아무 작업도 수행하지 않으며 매개 변수로 전달된 개체의 수명을 연장하는 것 외에는 부작용이 발생하지 않습니다.

적용 대상