通过

GCHandle.ToIntPtr(GCHandle) 方法

  • 参考

定义

命名空间:
System.Runtime.InteropServices
程序集:
System.Runtime.InteropServices.dll
程序集:
System.Runtime.dll
程序集:
mscorlib.dll
程序集:
netstandard.dll
Source:
GCHandle.cs
Source:
GCHandle.cs
Source:
GCHandle.cs

返回 GCHandle 对象的内部整数表示形式。

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

参数

value
GCHandle

要从中检索内部整数表示形式的 GCHandle 对象。

返回

IntPtr

nativeint

表示 GCHandle 对象的 IntPtr 对象。

示例

下面的代码示例演示一个 App 类，该类使用 GCHandle.Alloc 方法创建托管对象的句柄，从而阻止收集托管对象。 对 方法的 EnumWindows 调用传递委托和托管对象 (声明为托管类型，但不) 显示，并将句柄 IntPtr 强制转换为 对象。 非托管函数将类型作为回调函数的参数传递回调用方。

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

适用于