Windows服務是一個層上的進程;爲了成爲服務，應用程序必須連接到服務控制管理器並宣佈哪些服務可用。此連接在ADVAPI32.DLL庫中處理。建立此連接後，庫維護一個線程，等待來自服務控制管理器的命令，然後該服務控制管理器可以隨意啓動和停止服務。我不相信這個過程需要在最後一個服務終止時退出。雖然這是通常發生的事情，但在最後一個服務進入「已停止」狀態後，與服務控制管理器的鏈接結束可能會在流程實際終止之前發生，並釋放尚未明確釋放的資源。
Windows服務API包含的功能使您可以獲取託管服務的進程的進程ID。一個進程可能承載多個服務，因此當您感興趣的服務終止時，進程可能不會真正退出，但您應該使用SQL Server來保證安全。不幸的是，.NET Framework不公開這個功能。但是，它確實將句柄公開給它在內部用於API調用的服務，並且可以使用它來創建自己的API調用。然後，通過一些P/Invoke，您可以獲得Windows服務進程的進程ID，並從那裏獲得必要的權限，您可以打開一個進程的句柄，用於等待進程出口。
事情是這樣的：
[DllImport("advapi32")]
static extern bool QueryServiceStatusEx(IntPtr hService, int InfoLevel, ref SERVICE_STATUS_PROCESS lpBuffer, int cbBufSize, out int pcbBytesNeeded);
const int SC_STATUS_PROCESS_INFO = 0;
[StructLayout(LayoutKind.Sequential)]
struct SERVICE_STATUS_PROCESS
{
public int dwServiceType;
public int dwCurrentState;
public int dwControlsAccepted;
public int dwWin32ExitCode;
public int dwServiceSpecificExitCode;
public int dwCheckPoint;
public int dwWaitHint;
public int dwProcessId;
public int dwServiceFlags;
}
const int SERVICE_WIN32_OWN_PROCESS = 0x00000010;
const int SERVICE_RUNS_IN_SYSTEM_PROCESS = 0x00000001;
public static void StopServiceAndWaitForExit(string serviceName)
{
using (ServiceController controller = new ServiceController(serviceName))
{
SERVICE_STATUS_PROCESS ssp = new SERVICE_STATUS_PROCESS();
int ignored;
// Obtain information about the service, and specifically its hosting process,
// from the Service Control Manager.
if (!QueryServiceStatusEx(controller.ServiceHandle.DangerousGetHandle(), SC_STATUS_PROCESS_INFO, ref ssp, Marshal.SizeOf(ssp), out ignored))
throw new Exception("Couldn't obtain service process information.");
// A few quick sanity checks that what the caller wants is *possible*.
if (ssp.dwServiceType != SERVICE_WIN32_OWN_PROCESS)
throw new Exception("Can't wait for the service's hosting process to exit because there may be multiple services in the process (dwServiceType is not SERVICE_WIN32_OWN_PROCESS");
if ((ssp.dwServiceFlags & SERVICE_RUNS_IN_SYSTEM_PROCESS) != 0)
throw new Exception("Can't wait for the service's hosting process to exit because the hosting process is a critical system process that will not exit (SERVICE_RUNS_IN_SYSTEM_PROCESS flag set)");
if (ssp.dwProcessId == 0)
throw new Exception("Can't wait for the service's hosting process to exit because the process ID is not known.");
// Note: It is possible for the next line to throw an ArgumentException if the
// Service Control Manager's information is out-of-date (e.g. due to the process
// having *just* been terminated in Task Manager) and the process does not really
// exist. This is a race condition. The exception is the desirable result in this
// case.
using (Process process = Process.GetProcessById(ssp.dwProcessId))
{
// EDIT: There is no need for waiting in a separate thread, because MSDN says "The handles are valid until closed, even after the process or thread they represent has been terminated." (http://msdn.microsoft.com/en-us/library/windows/desktop/ms684868%28v=vs.85%29.aspx), so to keep things in the same thread, the process HANDLE should be opened from the process id before the service is stopped, and the Wait should be done after that.
// Response to EDIT: What you report is true, but the problem is that the handle isn't actually opened by Process.GetProcessById. It's only opened within the .WaitForExit method, which won't return until the wait is complete. Thus, if we try the wait on the current therad, we can't actually do anything until it's done, and if we defer the check until after the process has completed, it won't be possible to obtain a handle to it any more.
// The actual wait, using process.WaitForExit, opens a handle with the SYNCHRONIZE
// permission only and closes the handle before returning. As long as that handle
// is open, the process can be monitored for termination, but if the process exits
// before the handle is opened, it is no longer possible to open a handle to the
// original process and, worse, though it exists only as a technicality, there is
// a race condition in that another process could pop up with the same process ID.
// As such, we definitely want the handle to be opened before we ask the service
// to close, but since the handle's lifetime is only that of the call to WaitForExit
// and while WaitForExit is blocking the thread we can't make calls into the SCM,
// it would appear to be necessary to perform the wait on a separate thread.
ProcessWaitForExitData threadData = new ProcessWaitForExitData();
threadData.Process = process;
Thread processWaitForExitThread = new Thread(ProcessWaitForExitThreadProc);
processWaitForExitThread.IsBackground = Thread.CurrentThread.IsBackground;
processWaitForExitThread.Start(threadData);
// Now we ask the service to exit.
controller.Stop();
// Instead of waiting until the *service* is in the "stopped" state, here we
// wait for its hosting process to go away. Of course, it's really that other
// thread waiting for the process to go away, and then we wait for the thread
// to go away.
lock (threadData.Sync)
while (!threadData.HasExited)
Monitor.Wait(threadData.Sync);
}
}
}
class ProcessWaitForExitData
{
public Process Process;
public volatile bool HasExited;
public object Sync = new object();
}
static void ProcessWaitForExitThreadProc(object state)
{
ProcessWaitForExitData threadData = (ProcessWaitForExitData)state;
try
{
threadData.Process.WaitForExit();
}
catch {}
finally
{
lock (threadData.Sync)
{
threadData.HasExited = true;
Monitor.PulseAll(threadData.Sync);
}
}
}
Hrm，這回答了爲什麼。任何想法，但一個很好的解決方法？ – Dave 2009-05-19 21:18:16