[DllImport("user32.dll")]
static extern IntPtr SetWindowsHookEx(HookType hook, HookProc callback,
IntPtr hMod, uint dwThreadId);
A HookType constant specifying the type of hook to install.
A HookProc delegate representing the hook procedure method.
This will enable you to install application hooks. However, you cannot implement global hooks in Microsoft .NET Framework. To install a global hook, a hook must have a native dynamic-link library (DLL) export to inject itself in another process that requires a valid, consistent function to call into. This requires a DLL export, which .NET Framework does not support. Managed code has no concept of a consistent value for a function pointer because these function pointers are proxies that are built dynamically.
Remember to keep the HookProc delegate alive manually, otherwise the garbage collector will clean up your hook delegate eventually, resulting in your code throwing a System.NullReferenceException.
// this sample installs a keyboard hook
using System.Windows.Forms;
public class MyClass
{
private HookProc myCallbackDelegate = null;
public MyClass()
{
// initialize our delegate
this.myCallbackDelegate = new HookProc(this.MyCallbackFunction);
// setup a keyboard hook
SetWindowsHookEx(HookType.WH_KEYBOARD, this.myCallbackDelegate, IntPtr.Zero, AppDomain.GetCurrentThreadId());
}
[DllImport("user32.dll")]
protected static extern IntPtr SetWindowsHookEx(HookType code, HookProc func, IntPtr hInstance, int threadID);
private void MyCallbackFunction(int code, IntPtr wParam, IntPtr lParam)
{
// we can convert the 2nd parameter (the key code) to a System.Windows.Forms.Keys enum constant
Keys keyPressed = (Keys)wParam.ToInt32();
Console.WriteLine(keyPressed);
}
}
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SetWindowsHookEx on MSDN
MSDN example of a mouse hook in C#: http://support.microsoft.com/default.aspx?scid=kb;en-us;318804#3
MSDN article on hooks in .NET: http://msdn.microsoft.com/msdnmag/issues/02/10/CuttingEdge/