Call has been made on garbage collected delegate in C#?

by

The problem is that:

hhook = SetWindowsHookEx(WH_KEYBOARD_LL, hookProc, hInstance, 0);

is just syntactic sugar for:

hhook = SetWindowsHookEx(WH_KEYBOARD_LL, new keyboardHookProc(hookProc), hInstance, 0);

and so the keyboardHookProc object is just local and will get disposed of since SetWindowsHookEx doesn’t do anything to actually hold onto it in the managed world.

To fix this, up at the top where you define your member variables, add one more like this:

IntPtr hhook = IntPtr.Zero
private keyboardHookProc hookProcDelegate;

then change your constructor to be:

public globalKeyboardHook()
{
    hookProcDelegate = hookProc;
    hook();
}

and then change your hook() method to be:

public void hook()
{
    IntPtr hInstance = LoadLibrary("User32");
    hhook = SetWindowsHookEx(WH_KEYBOARD_LL, hookProcDelegate, hInstance, 0);
}

That way you’re using a delegate that is stored as a member variable and will be alive as long as your globalKeyboardHook object is alive.

More Related Contents:

  1. How to write Unicode characters to the console?
  2. Calculate MD5 checksum for a file
  3. Cannot delete directory with Directory.Delete(path, true)
  4. Detect Windows version in .NET
  5. Difference between ref and out parameters in .NET [duplicate]
  6. ‘using’ statement vs ‘try finally’
  7. Implicit typing; why just local variables?
  8. How to change symbol for decimal point in double.ToString()?
  9. method overloading vs optional parameter in C# 4.0 [duplicate]
  10. STAThread and multithreading
  11. How to find the 3rd Friday in a month with C#?
  12. If strings are immutable in .NET, then why does Substring take O(n) time?
  13. string.ToLower() and string.ToLowerInvariant()
  14. How do I get the available wifi APs and their signal strength in .net?
  15. Why generic IList does not inherit non-generic IList
  16. The call stack does not say “where you came from”, but “where you are going next”?
  17. How to split csv whose columns may contain comma
  18. Populate TreeView with file system directory structure
  19. How can I data bind a list of strings to a ListBox in WPF/WP7?
  20. Regex nested parentheses
  21. .Include() vs .Load() performance in EntityFramework
  22. What are some alternatives to RegistryKey.OpenBaseKey in .NET 3.5?
  23. How do I prevent a WCF service from enter a faulted state?
  24. Is there a .NET equivalent to SQL Server’s newsequentialid()
  25. Directly modifying List elements
  26. Regex for Money
  27. Convert Kinect ColorImageFrame to Bitmap
  28. What is the equivalent of bigint in C#?
  29. method without access modifier
  30. Detecting a password-protected document

Leave a Comment