CoWaitForMultipleHandles API的行为不像logging

这是我看到的另一个问题引发的。 阅读可能太长，请耐心等待。

显然， CoWaitForMultipleHandles行为不像MSDN上logging的那样。

下面的代码（基于原始问题）是一个控制台应用程序，它启动一个testingWin32窗口的STA线程，并尝试发布和泵送一些消息。 它在CoWaitForMultipleHandles上做了三个不同的testing，都没有 COWAIT_WAITALL标志。

testing＃1旨在validation这一点 ：

COWAIT_INPUTAVAILABLE如果已设置，则即使input已经被查看（但未被删除），但对CoWaitForMultipleHandles的调用将返回S_OK，如果队列中存在input，则会调用另一个函数（例如PeekMessage）。

这不会发生， CoWaitForMultipleHandles阻塞，并不会返回，直到等待手柄信号。 我假设任何挂起的消息应该被视为input （与MWMO_INPUTAVAILABLE的MsgWaitForMultipleObjectsEx相同，预计工作）。

testing＃2旨在validation这一点 ：

COWAIT_DISPATCH_WINDOW_MESSAGES允许从ASTA或STA中的CoWaitForMultipleHandles分派窗口消息。 在ASTA中默认是没有窗口消息派发，STA中的默认只是一小组调度的特殊的消息。 该值在MTA中没有意义，并被忽略。

这也不pipe用。 当CoWaitForMultipleHandles调用COWAIT_DISPATCH_WINDOW_MESSAGES时，会立即返回错误CO_E_NOT_SUPPORTED （0x80004021）。 如果是COWAIT_DISPATCH_WINDOW_MESSAGES | COWAIT_DISPATCH_CALLS的组合 COWAIT_DISPATCH_WINDOW_MESSAGES | COWAIT_DISPATCH_CALLS ，呼叫块但不会泵送任何消息。

testing＃3演示了我可以使CoWaitForMultipleHandles泵送调用线程的Windows消息队列的唯一方法。 这是COWAIT_DISPATCH_WINDOW_MESSAGES | COWAIT_DISPATCH_CALLS | COWAIT_INPUTAVAILABLE的组合 COWAIT_DISPATCH_WINDOW_MESSAGES | COWAIT_DISPATCH_CALLS | COWAIT_INPUTAVAILABLE COWAIT_DISPATCH_WINDOW_MESSAGES | COWAIT_DISPATCH_CALLS | COWAIT_INPUTAVAILABLE 。 这确实泵和发送消息，虽然显然这是一个无证的行为。

testing代码 （一个准备运行的控制台应用程序）：

 using System; using System.Runtime.InteropServices; using System.Threading; using System.Threading.Tasks; namespace ConsoleTestApp { static class Program { // Main static void Main(string[] args) { Console.WriteLine("Starting an STA thread..."); RunStaThread(); Console.WriteLine("\nSTA thread finished."); Console.WriteLine("Press Enter to exit."); Console.ReadLine(); } // start and run an STA thread static void RunStaThread() { var thread = new Thread(() => { // create a simple Win32 window IntPtr hwnd = CreateTestWindow(); // Post some WM_TEST messages Console.WriteLine("Post some WM_TEST messages..."); NativeMethods.PostMessage(hwnd, NativeMethods.WM_TEST, new IntPtr(1), IntPtr.Zero); NativeMethods.PostMessage(hwnd, NativeMethods.WM_TEST, new IntPtr(2), IntPtr.Zero); NativeMethods.PostMessage(hwnd, NativeMethods.WM_TEST, new IntPtr(3), IntPtr.Zero); // Test #1 Console.WriteLine("\nTest #1. CoWaitForMultipleHandles with COWAIT_INPUTAVAILABLE only, press Enter to stop..."); var task = ReadLineAsync(); uint index; var result = NativeMethods.CoWaitForMultipleHandles( NativeMethods.COWAIT_INPUTAVAILABLE, NativeMethods.INFINITE, 1, new[] { task.AsUnmanagedHandle() }, out index); Console.WriteLine("Result: " + result + ", pending messages in the queue: " + (NativeMethods.GetQueueStatus(0x1FF) >> 16 != 0)); // Test #2 Console.WriteLine("\nTest #2. CoWaitForMultipleHandles with COWAIT_DISPATCH_WINDOW_MESSAGES | COWAIT_DISPATCH_CALLS, press Enter to stop..."); task = ReadLineAsync(); result = NativeMethods.CoWaitForMultipleHandles( NativeMethods.COWAIT_DISPATCH_WINDOW_MESSAGES | NativeMethods.COWAIT_DISPATCH_CALLS, NativeMethods.INFINITE, 1, new[] { task.AsUnmanagedHandle() }, out index); Console.WriteLine("Result: " + result + ", pending messages in the queue: " + (NativeMethods.GetQueueStatus(0x1FF) >> 16 != 0)); // Test #3 Console.WriteLine("\nTest #3. CoWaitForMultipleHandles with COWAIT_DISPATCH_WINDOW_MESSAGES | COWAIT_DISPATCH_CALLS | COWAIT_INPUTAVAILABLE, press Enter to stop..."); task = ReadLineAsync(); result = NativeMethods.CoWaitForMultipleHandles( NativeMethods.COWAIT_DISPATCH_WINDOW_MESSAGES | NativeMethods.COWAIT_DISPATCH_CALLS | NativeMethods.COWAIT_INPUTAVAILABLE, NativeMethods.INFINITE, 1, new[] { task.AsUnmanagedHandle() }, out index); Console.WriteLine("Result: " + result + ", pending messages in the queue: " + (NativeMethods.GetQueueStatus(0x1FF) >> 16 != 0)); }); thread.SetApartmentState(ApartmentState.STA); thread.Start(); thread.Join(); } // // Helpers // // create a window to handle messages static IntPtr CreateTestWindow() { // Create a simple Win32 window var hwndStatic = NativeMethods.CreateWindowEx(0, "Static", String.Empty, NativeMethods.WS_POPUP, 0, 0, 0, 0, NativeMethods.HWND_MESSAGE, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero); // subclass it with a custom WndProc IntPtr prevWndProc = IntPtr.Zero; NativeMethods.WndProc newWndProc = (hwnd, msg, wParam, lParam) => { if (msg == NativeMethods.WM_TEST) Console.WriteLine("WM_TEST processed: " + wParam); return NativeMethods.CallWindowProc(prevWndProc, hwnd, msg, wParam, lParam); }; prevWndProc = NativeMethods.SetWindowLong(hwndStatic, NativeMethods.GWL_WNDPROC, Marshal.GetFunctionPointerForDelegate(newWndProc)); if (prevWndProc == IntPtr.Zero) throw new ApplicationException(); return hwndStatic; } // call Console.ReadLine on a pool thread static Task<string> ReadLineAsync() { return Task.Run(() => Console.ReadLine()); } // get Win32 waitable handle of Task object static IntPtr AsUnmanagedHandle(this Task task) { return ((IAsyncResult)task).AsyncWaitHandle.SafeWaitHandle.DangerousGetHandle(); } } // Interop static class NativeMethods { [DllImport("user32")] public static extern IntPtr SetWindowLong(IntPtr hwnd, int nIndex, IntPtr dwNewLong); [DllImport("user32")] public static extern IntPtr CallWindowProc(IntPtr lpPrevWndFunc, IntPtr hwnd, uint msg, IntPtr wParam, IntPtr lParam); [DllImport("user32.dll")] public static extern IntPtr CreateWindowEx( uint dwExStyle, string lpClassName, string lpWindowName, uint dwStyle, int x, int y, int nWidth, int nHeight, IntPtr hWndParent, IntPtr hMenu, IntPtr hInstance, IntPtr lpParam); [DllImport("user32.dll")] public static extern bool PostMessage(IntPtr hwnd, uint msg, IntPtr wParam, IntPtr lParam); [DllImport("user32.dll")] public static extern int MessageBox(IntPtr hwnd, string text, String caption, int options); [DllImport("ole32.dll", SetLastError = true)] public static extern uint CoWaitForMultipleHandles(uint dwFlags, uint dwTimeout, int cHandles, IntPtr[] pHandles, out uint lpdwindex); [DllImport("user32.dll")] public static extern uint GetQueueStatus(uint flags); [UnmanagedFunctionPointer(CallingConvention.StdCall)] public delegate IntPtr WndProc(IntPtr hwnd, uint msg, IntPtr wParam, IntPtr lParam); public static IntPtr HWND_MESSAGE = new IntPtr(-3); public const int GWL_WNDPROC = -4; public const uint WS_POPUP = 0x80000000; public const uint WM_USER = 0x0400; public const uint WM_TEST = WM_USER + 1; public const uint COWAIT_WAITALL = 1; public const uint COWAIT_ALERTABLE = 2; public const uint COWAIT_INPUTAVAILABLE = 4; public const uint COWAIT_DISPATCH_CALLS = 8; public const uint COWAIT_DISPATCH_WINDOW_MESSAGES = 0x10; public const uint RPC_S_CALLPENDING = 0x80010115; public const uint WAIT_TIMEOUT = 0x00000102; public const uint WAIT_FAILED = 0xFFFFFFFF; public const uint WAIT_OBJECT_0 = 0; public const uint WAIT_ABANDONED_0 = 0x00000080; public const uint WAIT_IO_COMPLETION = 0x000000C0; public const uint INFINITE = 0xFFFFFFFF; } } 

输出：

启动STA线程...
发布一些WM_TEST消息...

 testing＃1。  CoWaitForMultipleHandles只有COWAIT_INPUTAVAILABLE，按Enter停止...

结果：0，等待队列中的消息：True

 testing＃2。  CoWaitForMultipleHandles与COWAIT_DISPATCH_WINDOW_MESSAGES |  COWAIT_DISPATCH_CALLS，按Enter停止...

结果：0，等待队列中的消息：True

 testing＃3  CoWaitForMultipleHandles与COWAIT_DISPATCH_WINDOW_MESSAGES |  COWAIT_DISPATCH_CALLS |  COWAIT_INPUTAVAILABLE，按Enter停止...
 WM_TEST处理：1
 WM_TEST处理：2
 WM_TEST处理：3

结果：0，等待队列中的消息：False

 STA线程完成。
按Enter键退出。

所有的testing都是在Windows 8.1 Pro 64bit + NET v4.5.1下完成的。

• 我误读了文档还是错过了其他的东西？

• 我应该报告这是一个错误（至less，在文档中的错误）？

• 应该避免使用CoWaitForMultipleHandles并用基于MsgWaitForMultipleObjectsEx （其行为符合文档）的解决schemereplace？

[更新]在Windows 7下， COWAIT_DISPATCH_WINDOW_MESSAGES和COWAIT_DISPATCH_CALLS被支持， CoWaitForMultipleHandles失败， E_INVALIDARG （0x80070057）。 当用零作为标志进行调用时，它不会被泵送。