GCHandle.ToIntPtr(GCHandle) GCHandle.ToIntPtr(GCHandle) GCHandle.ToIntPtr(GCHandle) GCHandle.ToIntPtr(GCHandle) Method

定義

傳回 GCHandle 物件的內部整數表示。Returns the internal integer representation of a GCHandle object.

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

參數

value
GCHandle GCHandle GCHandle GCHandle

GCHandle 物件,要從此物件擷取內部整數表示。A GCHandle object to retrieve an internal integer representation from.

傳回

IntPtr 物件,表示 GCHandle 物件。An IntPtr object that represents a GCHandle object.

範例

下列程式App代碼範例所示範的類別,會GCHandle.Alloc使用方法建立 managed 物件的控制碼,以防止收集 managed 物件。The following code example shows an App class that creates a handle to a managed object using the GCHandle.Alloc method, which prevents the managed object from being collected. EnumWindows方法的呼叫會傳遞委派和 managed 物件(兩者都宣告為 managed 類型,但不會顯示),並將控制碼轉換IntPtr成物件。A call to the EnumWindows method passes a delegate and a managed object (both declared as managed types, but not shown), and casts the handle to an IntPtr object. 非受控函式會將型別傳遞回呼叫端做為回呼函式的參數。The unmanaged function passes the type back to the caller as a parameter of the callback function.

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

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();
    }

    [SecurityPermission(SecurityAction.Demand, UnmanagedCode = true)]
    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

適用於