GCHandle.Alloc Yöntem

Kaynak:

GCHandle.cs

Kaynak:

GCHandle.cs

Kaynak:

GCHandle.cs

public:
 static System::Runtime::InteropServices::GCHandle Alloc(System::Object ^ value);

[System.Security.SecurityCritical]
public static System.Runtime.InteropServices.GCHandle Alloc (object value);

public static System.Runtime.InteropServices.GCHandle Alloc (object? value);

public static System.Runtime.InteropServices.GCHandle Alloc (object value);

[<System.Security.SecurityCritical>]
static member Alloc : obj -> System.Runtime.InteropServices.GCHandle

static member Alloc : obj -> System.Runtime.InteropServices.GCHandle

Public Shared Function Alloc (value As Object) As GCHandle

Parametreler

Döndürülenler

Nesneyi çöp toplamaya karşı koruyan yeni GCHandle bir. Bu GCHandle , artık gerekli olmadığında ile serbest Free() bırakılmalıdır.

Öznitelikler

SecurityCriticalAttribute

Örnekler

Aşağıdaki örnek, yönetilen nesnenin toplanmasını engelleyen yöntemini kullanarak GCHandle.Alloc yönetilen bir nesneye tanıtıcı oluşturan bir sınıfı gösterirApp. yöntemine yapılan EnumWindows bir çağrı, bir temsilciyi ve yönetilen nesneyi (her ikisi de yönetilen türler olarak bildirilir, ancak gösterilmez) geçirir ve tanıtıcıyı öğesine IntPtrdönüştürür. Yönetilmeyen işlev, geri çağırma işlevinin parametresi olarak türü çağırana geri geçirir.

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

Açıklamalar

Normal tanıtıcılar opaktır; bu da içerdiği nesnenin adresini tanıtıcı aracılığıyla çözümleyemeyeceğiniz anlamına gelir.

Ayrıca bkz.

• GCHandleType

Kaynak:

GCHandle.cs

Kaynak:

GCHandle.cs

Kaynak:

GCHandle.cs

public:
 static System::Runtime::InteropServices::GCHandle Alloc(System::Object ^ value, System::Runtime::InteropServices::GCHandleType type);

[System.Security.SecurityCritical]
public static System.Runtime.InteropServices.GCHandle Alloc (object value, System.Runtime.InteropServices.GCHandleType type);

public static System.Runtime.InteropServices.GCHandle Alloc (object? value, System.Runtime.InteropServices.GCHandleType type);

public static System.Runtime.InteropServices.GCHandle Alloc (object value, System.Runtime.InteropServices.GCHandleType type);

[<System.Security.SecurityCritical>]
static member Alloc : obj * System.Runtime.InteropServices.GCHandleType -> System.Runtime.InteropServices.GCHandle

static member Alloc : obj * System.Runtime.InteropServices.GCHandleType -> System.Runtime.InteropServices.GCHandle

Public Shared Function Alloc (value As Object, type As GCHandleType) As GCHandle

Parametreler

Döndürülenler

Belirtilen türden yeni GCHandle bir. Bu GCHandle , artık gerekli olmadığında ile serbest Free() bırakılmalıdır.

Öznitelikler

SecurityCriticalAttribute

Özel durumlar

Ayrıca bkz.

• GCHandleType