GCHandle.ToIntPtr(GCHandle) Método

Definición

Espacio de nombres:

System.Runtime.InteropServices

Ensamblado:

mscorlib.dll

Devuelve la representación entera interna de un GCHandle objeto .

public:
 static IntPtr ToIntPtr(System::Runtime::InteropServices::GCHandle value);

public static IntPtr ToIntPtr(System.Runtime.InteropServices.GCHandle value);

static member ToIntPtr : System.Runtime.InteropServices.GCHandle -> nativeint

Public Shared Function ToIntPtr (value As GCHandle) As IntPtr

Parámetros

value

GCHandle

Objeto GCHandle del que se va a recuperar una representación de entero interna.

Devoluciones

IntPtr

nativeint

Objeto IntPtr que representa un GCHandle objeto .

Ejemplos

En el ejemplo de código siguiente se muestra una App clase que crea un identificador para un objeto administrado mediante el GCHandle.Alloc método , lo que impide que se recopile el objeto administrado. Una llamada al EnumWindows método pasa un delegado y un objeto administrado (ambos declarados como tipos administrados, pero no mostrados) y convierte el identificador en un IntPtr objeto . La función no administrada pasa el tipo al autor de la llamada como parámetro de la función de devolución de llamada.

using System;
using System.IO;
using System.Threading;
using System.Windows.Forms;
using System.Runtime.InteropServices;

public delegate bool CallBack(int handle, IntPtr param);

internal static class NativeMethods
{
    // passing managed object as LPARAM
    // BOOL EnumWindows(WNDENUMPROC lpEnumFunc, LPARAM lParam);

    [DllImport("user32.dll")]
    internal static extern bool EnumWindows(CallBack cb, IntPtr param);
}

public class App
{
    public static void Main()
    {
        Run();
    }

    public static void Run()
    {
        TextWriter tw = Console.Out;
        GCHandle gch = GCHandle.Alloc(tw);

        CallBack cewp = new CallBack(CaptureEnumWindowsProc);

        // platform invoke will prevent delegate to be garbage collected
        // before call ends

        NativeMethods.EnumWindows(cewp, GCHandle.ToIntPtr(gch));
        gch.Free();
    }

    private static bool CaptureEnumWindowsProc(int handle, IntPtr param)
    {
        GCHandle gch = GCHandle.FromIntPtr(param);
        TextWriter tw = (TextWriter)gch.Target;
        tw.WriteLine(handle);
        return true;
    }
}

Imports System.IO
Imports System.Threading
Imports System.Windows.Forms
Imports System.Runtime.InteropServices
Imports System.Security.Permissions

Public Delegate Function CallBack(ByVal handle As Integer, ByVal param As IntPtr) As Boolean


Friend Module NativeMethods

    ' passing managed object as LPARAM
    ' BOOL EnumWindows(WNDENUMPROC lpEnumFunc, LPARAM lParam);
    <DllImport("user32.dll")>
    Friend Function EnumWindows(ByVal cb As CallBack, ByVal param As IntPtr) As Boolean
    End Function
End Module


Module App

    Sub Main()

        Run()

    End Sub

    <SecurityPermission(SecurityAction.Demand, UnmanagedCode:=True)>
    Sub Run()

        Dim tw As TextWriter = Console.Out
        Dim gch As GCHandle = GCHandle.Alloc(tw)

        Dim cewp As CallBack
        cewp = AddressOf CaptureEnumWindowsProc

        ' platform invoke will prevent delegate to be garbage collected
        ' before call ends
        NativeMethods.EnumWindows(cewp, GCHandle.ToIntPtr(gch))
        gch.Free()

    End Sub


    Function CaptureEnumWindowsProc(ByVal handle As Integer, ByVal param As IntPtr) As Boolean
        Dim gch As GCHandle = GCHandle.FromIntPtr(param)
        Dim tw As TextWriter = CType(gch.Target, TextWriter)
        tw.WriteLine(handle)
        Return True

    End Function
End Module