GCHandle.Alloc GCHandle.Alloc GCHandle.Alloc GCHandle.Alloc Method

定義

配置指定物件的控制代碼。Allocates a handle for the specified object.

多載

Alloc(Object) Alloc(Object) Alloc(Object) Alloc(Object)

配置 Normal 控制代碼給指定的物件。Allocates a Normal handle for the specified object.

Alloc(Object, GCHandleType) Alloc(Object, GCHandleType) Alloc(Object, GCHandleType) Alloc(Object, GCHandleType)

配置指定類型的控制代碼給指定的物件。Allocates a handle of the specified type for the specified object.

Alloc(Object) Alloc(Object) Alloc(Object) Alloc(Object)

配置 Normal 控制代碼給指定的物件。Allocates a Normal handle for the specified object.

public:
 static System::Runtime::InteropServices::GCHandle Alloc(System::Object ^ value);
[System.Security.SecurityCritical]
public static System.Runtime.InteropServices.GCHandle Alloc (object value);
static member Alloc : obj -> System.Runtime.InteropServices.GCHandle
Public Shared Function Alloc (value As Object) As GCHandle

參數

value
Object Object Object Object

使用 GCHandle 的物件。The object that uses the GCHandle.

傳回

保護物件不被記憶體回收的新 GCHandleA new GCHandle that protects the object from garbage collection. 當不再需要時,這個 GCHandle 必須使用 Free() 來釋放。This GCHandle must be released with Free() when it is no longer needed.

範例

下列範例顯示App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 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。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. 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

備註

Normal控制碼是不透明的,這表示您無法透過控制碼解析其所包含之物件的位址。Normal handles are opaque, which means that you cannot resolve the address of the object it contains through the handle.

安全性

SecurityCriticalAttribute
需要完全信任立即呼叫者。requires full trust for the immediate caller. 部分信任或透明的程式碼無法使用這個成員。This member cannot be used by partially trusted or transparent code.

另請參閱

Alloc(Object, GCHandleType) Alloc(Object, GCHandleType) Alloc(Object, GCHandleType) Alloc(Object, GCHandleType)

配置指定類型的控制代碼給指定的物件。Allocates a handle of the specified type for the specified object.

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);
static member Alloc : obj * System.Runtime.InteropServices.GCHandleType -> System.Runtime.InteropServices.GCHandle
Public Shared Function Alloc (value As Object, type As GCHandleType) As GCHandle

參數

value
Object Object Object Object

使用 GCHandle 的物件。The object that uses the GCHandle.

type
GCHandleType GCHandleType GCHandleType GCHandleType

GCHandleType 值的其中之一,指出要建立的 GCHandle 型別。One of the GCHandleType values, indicating the type of GCHandle to create.

傳回

指定型別的新 GCHandleA new GCHandle of the specified type. 當不再需要時,這個 GCHandle 必須使用 Free() 來釋放。This GCHandle must be released with Free() when it is no longer needed.

例外狀況

不可以 Pin 含有非基本 (非 Blittable) 成員的執行個體。An instance with nonprimitive (non-blittable) members cannot be pinned.

安全性

SecurityCriticalAttribute
需要完全信任立即呼叫者。requires full trust for the immediate caller. 部分信任或透明的程式碼無法使用這個成員。This member cannot be used by partially trusted or transparent code.

另請參閱

適用於