已经在C＃中对垃圾收集的委托进行了调用？

分类：编程问答

如何解决已经在C＃中对垃圾收集的委托进行了调用？

| 我一直在使用找到的这个密钥挂钩脚本，但是在程序中使用它几秒钟后，我仍然出现错误。错误消息说。已在垃圾回收委托\'keylogger！Utilities.globalKeyboardHook + keyboardHookProc :: Invoke \'上进行了调用。 我怎样才能解决这个问题？ 
namespace Utilities
{
/// <summary>
/// A class that manages a global low level keyboard hook
/// </summary>
class globalKeyboardHook
{

    #region Constant,Structure and Delegate Definitions
    /// <summary>
    /// defines the callback type for the hook
    /// </summary>
    public delegate int keyboardHookProc(int code,int wParam,ref keyboardHookStruct lParam);

    public struct keyboardHookStruct
    {
        public int vkCode;
        public int scanCode;
        public int flags;
        public int time;
        public int dwExtraInfo;
    }

    const int WH_KEYBOARD_LL = 13;
    const int WM_KEYDOWN = 0x100;
    const int WM_KEYUP = 0x101;
    const int WM_SYSKEYDOWN = 0x104;
    const int WM_SYSKEYUP = 0x105;
    #endregion

    #region Instance Variables
    /// <summary>
    /// The collections of keys to watch for
    /// </summary>
    public List<Keys> HookedKeys = new List<Keys>();
    /// <summary>
    /// Handle to the hook,need this to unhook and call the next hook
    /// </summary>
    IntPtr hhook = IntPtr.Zero;
    #endregion

    #region Events
    /// <summary>
    /// Occurs when one of the hooked keys is pressed
    /// </summary>
    public event KeyEventHandler KeyDown;
    /// <summary>
    /// Occurs when one of the hooked keys is released
    /// </summary>
    public event KeyEventHandler KeyUp;
    #endregion

    #region Constructors and Destructors
    /// <summary>
    /// Initializes a new instance of the <see cref=\"globalKeyboardHook\"/> class and installs the keyboard hook.
    /// </summary>
    public globalKeyboardHook()
    {
        hook();
    }

    /// <summary>
    /// Releases unmanaged resources and performs other cleanup operations before the
    /// <see cref=\"globalKeyboardHook\"/> is reclaimed by garbage collection and uninstalls the keyboard hook.
    /// </summary>
    ~globalKeyboardHook()
    {
        unhook();
    }
    #endregion

    #region Public Methods
    /// <summary>
    /// Installs the global hook
    /// </summary>
    public void hook()
    {

        IntPtr hInstance = LoadLibrary(\"User32\");
        hhook = SetWindowsHookEx(WH_KEYBOARD_LL,hookProc,hInstance,0);
    }

    /// <summary>
    /// Uninstalls the global hook
    /// </summary>
    public void unhook()
    {
        UnhookWindowsHookEx(hhook);
    }

    /// <summary>
    /// The callback for the keyboard hook
    /// </summary>
    /// <param name=\"code\">The hook code,if it isn\'t >= 0,the function shouldn\'t do anyting</param>
    /// <param name=\"wParam\">The event type</param>
    /// <param name=\"lParam\">The keyhook event information</param>
    /// <returns></returns>
    public int hookProc(int code,ref keyboardHookStruct lParam)
    {
        if (code >= 0)
        {
            Keys key = (Keys)lParam.vkCode;
            if (HookedKeys.Contains(key))
            {
                KeyEventArgs kea = new KeyEventArgs(key);
                if ((wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN) && (KeyDown != null))
                {
                    KeyDown(this,kea);
                }
                else if ((wParam == WM_KEYUP || wParam == WM_SYSKEYUP) && (KeyUp != null))
                {
                    KeyUp(this,kea);
                }
                if (kea.Handled)
                    return 1;
            }
        }
        return CallNextHookEx(hhook,code,wParam,ref lParam);
    }
    #endregion

    #region DLL imports
    /// <summary>
    /// Sets the windows hook,do the desired event,one of hInstance or threadId must be non-null
    /// </summary>
    /// <param name=\"idHook\">The id of the event you want to hook</param>
    /// <param name=\"callback\">The callback.</param>
    /// <param name=\"hInstance\">The handle you want to attach the event to,can be null</param>
    /// <param name=\"threadId\">The thread you want to attach the event to,can be null</param>
    /// <returns>a handle to the desired hook</returns>
    [DllImport(\"user32.dll\")]
    static extern IntPtr SetWindowsHookEx(int idHook,keyboardHookProc callback,IntPtr hInstance,uint threadId);

    /// <summary>
    /// Unhooks the windows hook.
    /// </summary>
    /// <param name=\"hInstance\">The hook handle that was returned from SetWindowsHookEx</param>
    /// <returns>True if successful,false otherwise</returns>
    [DllImport(\"user32.dll\")]
    static extern bool UnhookWindowsHookEx(IntPtr hInstance);

    /// <summary>
    /// Calls the next hook.
    /// </summary>
    /// <param name=\"idHook\">The hook id</param>
    /// <param name=\"nCode\">The hook code</param>
    /// <param name=\"wParam\">The wparam.</param>
    /// <param name=\"lParam\">The lparam.</param>
    /// <returns></returns>
    [DllImport(\"user32.dll\")]
    static extern int CallNextHookEx(IntPtr idHook,int nCode,ref keyboardHookStruct lParam);

    /// <summary>
    /// Loads the library.
    /// </summary>
    /// <param name=\"lpFileName\">Name of the library</param>
    /// <returns>A handle to the library</returns>
    [DllImport(\"kernel32.dll\")]
    static extern IntPtr LoadLibrary(string lpFileName);
    #endregion
    }
}
globalKeyboardHook类： 
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using System.IO;

namespace Utilities
{
/// <summary>
/// A class that manages a global low level keyboard hook
/// </summary>
class globalKeyboardHook : IDisposable
{

    private bool _disposed;

    #region Constant,need this to unhook and call the next hook
    /// </summary>
    IntPtr hhook = IntPtr.Zero;
    #endregion

    #region Events
    /// <summary>
    /// Occurs when one of the hooked keys is pressed
    /// </summary>
    public event KeyEventHandler KeyDown;
    /// <summary>
    /// Occurs when one of the hooked keys is released
    /// </summary>
    public event KeyEventHandler KeyUp;
    #endregion

    #region Constructors and Destructors
    /// <summary>
    /// Initializes a new instance of the <see cref=\"globalKeyboardHook\"/> class and installs the keyboard hook.
    /// </summary>
    public globalKeyboardHook()
    {
        hook();
        _disposed = false;
    }

    public void Dispose()
    {
        Dispose(true);

        // Use SupressFinalize in case a subclass
        // of this type implements a finalizer.
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        // If you need thread safety,use a lock around these 
        // operations,as well as in your methods that use the resource.
        if (!_disposed)
        {
            if (disposing)
            {
                unhook();
            }

            // Indicate that the instance has been disposed.
            _disposed = true;
        }
    }

    /// <summary>
    /// Releases unmanaged resources and performs other cleanup operations before the
    /// <see cref=\"globalKeyboardHook\"/> is reclaimed by garbage collection and uninstalls the keyboard hook.
    /// </summary>
    ~globalKeyboardHook()
    {
        Dispose();
    }
    #endregion

    #region Public Methods
    /// <summary>
    /// Installs the global hook
    /// </summary>
    public void hook()
    {
        IntPtr hInstance = LoadLibrary(\"User32\");
        hhook = SetWindowsHookEx(WH_KEYBOARD_LL,new keyboardHookProc(hookProc),ref keyboardHookStruct lParam);

    /// <summary>
    /// Loads the library.
    /// </summary>
    /// <param name=\"lpFileName\">Name of the library</param>
    /// <returns>A handle to the library</returns>
    [DllImport(\"kernel32.dll\")]
    static extern IntPtr LoadLibrary(string lpFileName);
    #endregion
    }
}
我使用IDisposable更新了代码。我可能对我应该做的事情很不满意，但仍然无法正常工作     

解决方法

        问题是： 
hhook = SetWindowsHookEx(WH_KEYBOARD_LL,hookProc,hInstance,0);
只是用于以下目的的语法糖： 
hhook = SetWindowsHookEx(WH_KEYBOARD_LL,new keyboardHookProc(hookProc),0);
因此，
keyboardHookProc
对象只是局部对象，将被丢弃，因为
SetWindowsHookEx
并没有做任何事情来实际托管在托管环境中。 要解决此问题，请在定义成员变量的顶部上方，再添加一个这样的变量： 
IntPtr hhook = IntPtr.Zero
private keyboardHookProc hookProcDelegate;
然后将您的构造函数更改为： 
public globalKeyboardHook()
{
    hookProcDelegate = hookProc;
    hook();
}
然后将您的
hook()
方法更改为： 
public void hook()
{
    IntPtr hInstance = LoadLibrary(\"User32\");
    hhook = SetWindowsHookEx(WH_KEYBOARD_LL,hookProcDelegate,0);
}
这样，您将使用一个存储为成员变量的委托，只要您的
globalKeyboardHook
对象处于活动状态，该代理就会处于活动状态。     ,        在我看来，您正在实例化globalKeyboardHook，然后让其获取垃圾。我猜您正在执行以下操作： 
public void InstallHook()
{
    var hook = new globalKeyboardHook();
}
您需要保留对globalKeyboardHook（）的引用，以防止对其进行垃圾回收。 
globalKeyboardHook hook;

public void InstallHook()
{
    hook = new globalKeyboardHook();
}
    ,        即使使用新代码，我仍然遇到上述错误，作为解决方案，我只是将委托的实例保留在类范围内，现在不再出现该错误。 
//do not forget to declare kbhproc class var   
this.kbhProc = new keyboardHookProc(hookProc);
hhook = SetWindowsHookEx(WH_KEYBOARD_LL,this.kbhProc /*new keyboardHookProc(hookProc)*/,0);
上面的代码基于问题的代码。     ,        我想添加此代码，以供将来参考，因为如果您有复杂的代码，它可能有助于理解Tim的答案，并可能调试正在发生的事情： callbackOnCollectedDelegate MDA https://docs.microsoft.com/zh-cn/dotnet/framework/debug-trace-profile/callbackoncollecteddelegate-mda     

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