Restart Manager

The Windows Restart Manager lets an installer find the applications that use the files it wants to replace, close them, and restart them afterwards. Dapplo.Windows has a package for each side:

Package	For	Main type
Dapplo.Windows.AppRestartManager	applications which should survive an update or a reboot	ApplicationRestartManager
Dapplo.Windows.InstallerManager	installers and updaters	InstallerRestartManager

dotnet add package Dapplo.Windows.AppRestartManager
dotnet add package Dapplo.Windows.InstallerManager

Namespaces used on this page: Dapplo.Windows.AppRestartManager, Dapplo.Windows.AppRestartManager.Enums, Dapplo.Windows.InstallerManager, Dapplo.Windows.InstallerManager.Enums, System.Reactive.Linq.

Application side

Register for restart

Register early, for example in Main. When an installer closes the application through the Restart Manager (or Windows Update restarts the PC and "Restart apps" is enabled), Windows starts it again with the command line you registered. Windows doesn't tell the new process that it was restarted, so register an argument that you only use for this and check for it.

// Early in Main: restart me with "/restore" when an installer or Windows Update closes me.
// Don't include the executable, Windows adds it. At most RestartMaxCmdLine (1024) characters.
ApplicationRestartManager.RegisterForRestart("/restore");

// Windows can't tell a process that it was restarted, check for your own argument instead
// (a manual start with the same argument returns true too)
if (ApplicationRestartManager.WasRestartRequested("/restore"))
{
    RestoreDocuments();
}

The flags exclude cases in which you don't want a restart. A restart after a crash or a hang only happens when the process was running for at least 60 seconds.

// Restart after an update, but not after a crash or hang (those restarts need 60 seconds of uptime anyway)
ApplicationRestartManager.RegisterForRestart("/restore",
    ApplicationRestartFlags.RestartNoCrash | ApplicationRestartFlags.RestartNoHang);

// No automatic restart anymore
ApplicationRestartManager.UnregisterForRestart();

ApplicationRestartFlags	Don't restart when
RestartNoCrash	the application crashed
RestartNoHang	the application hung
RestartNoPatch	the application is closed for an update
RestartNoReboot	the system restarts for an update

Being asked to close

Before the session ends (shutdown, restart, log off) and when an installer wants to close the application, Windows sends WM_QUERYENDSESSION and then WM_ENDSESSION to every top-level window. ListenForEndSession() gives you these messages of the SharedMessageWindow as EndSessionMessage, so this also works for console applications and services without windows.

• Answer a query (IsQuery) synchronously inside OnNext: Veto(reason) asks Windows not to end the session and shows the reason in the "apps are preventing shutdown" screen; CanEndSession = true (or not answering) allows it. The user can still choose to shut down anyway.
• EndSessionReason says why: ENDSESSION_CLOSEAPP is the Restart Manager (an installer), ENDSESSION_LOGOFF a log off, ENDSESSION_CRITICAL a forced shutdown.
• For WM_ENDSESSION with IsSessionEnding, the process can be ended as soon as OnNext returns: save synchronously, don't rely on marshalling to the UI thread.

// WM_QUERYENDSESSION and WM_ENDSESSION, received by the SharedMessageWindow.
// OnNext runs on the SharedMessageWindow thread, answer synchronously: no ObserveOn before the answer.
IDisposable subscription = ApplicationRestartManager.ListenForEndSession()
    .Subscribe(message =>
    {
        if (message.IsQuery)
        {
            // ENDSESSION_CLOSEAPP: an installer (Restart Manager) wants to replace files which this process uses
            bool isRestartManager = (message.EndSessionReason & EndSessionReasons.ENDSESSION_CLOSEAPP) != 0;
            if (HasUnsavedWork() && !isRestartManager)
            {
                // Windows shows the reason in its "apps are preventing shutdown" screen
                message.Veto("Unsaved changes");
            }
            // Not answering allows the session to end
        }
        else if (message.IsSessionEnding)
        {
            // WM_ENDSESSION: the process can be terminated as soon as this returns, save synchronously
            SaveState();
        }
    });

Windows Forms (FormClosing with CloseReason.WindowsShutDown) and WPF (Application.SessionEnding) report the same messages for their own windows; ListenForEndSession works without a UI framework.

Installer side

InstallerRestartManager.CreateSession() starts a Restart Manager session; dispose it to end the session. Register the files, processes or services you want to replace, then ask which processes use them.

using var session = InstallerRestartManager.CreateSession();
session.RegisterFiles(@"C:\Program Files\MyApp\MyApp.exe", @"C:\Program Files\MyApp\MyApp.Core.dll");

var processes = session.GetProcessesUsingResources(out RmRebootReason rebootReason);
foreach (var process in processes)
{
    Console.WriteLine($"{process.AppName} (PID {process.Process.ProcessId}, {process.ApplicationType}), can be restarted: {process.IsRestartable}");
}
if (rebootReason != RmRebootReason.RmRebootReasonNone)
{
    Console.WriteLine($"Replacing the files needs a reboot: {rebootReason}");
}

RmProcessInfo has AppName, Process.ProcessId (with Process.ProcessStartTime to tell a reused process id apart), ServiceShortName, ApplicationType (RmMainWindow, RmService, RmExplorer, RmConsole, RmCritical, ...), AppStatus, TerminalServicesSessionId and IsRestartable.

Replace files and restart the applications

Shutdown() asks the applications to close. The default, RmShutdownType.Graceful, fails with a Win32Exception when an application refuses (for example because of unsaved work), so nobody loses data. RmShutdownType.Force kills applications which don't respond; use it only when you must. RmShutdownType.OnlyRegistered (a flag, it can be combined with Force) only closes applications which registered for restart. After the files are replaced, Restart() starts the applications again which registered for restart.

using var session = InstallerRestartManager.CreateSession();
session.RegisterFiles(Directory.GetFiles(installDirectory, "*.dll"));

if (session.IsRebootRequired())
{
    Console.WriteLine("Can't update without a reboot, schedule the update instead");
    return;
}

try
{
    // Graceful (the default): asks the applications to close, fails when one of them refuses (e.g. unsaved work)
    session.Shutdown(statusCallback: percent => Console.WriteLine($"Closing applications: {percent}%"));
}
catch (Win32Exception ex)
{
    Console.WriteLine($"An application refused to close: {ex.Message}");
    // Only when you must: RmShutdownType.Force kills unresponsive applications, which can lose data
    return;
}

foreach (var file in Directory.GetFiles(newFilesDirectory))
{
    File.Copy(file, Path.Combine(installDirectory, Path.GetFileName(file)), overwrite: true);
}

// Restart the applications which registered for restart (RegisterApplicationRestart)
session.Restart();

IsRebootRequired() and GetRebootReason() query the Restart Manager again; when you also need the process list, use GetProcessesUsingResources(out rebootReason) which gives both.

RmRebootReason	Meaning
RmRebootReasonNone	no reboot needed
RmRebootReasonPermissionDenied	a process can't be closed with the current rights (run elevated)
RmRebootReasonSessionMismatch	a process runs in another session
RmRebootReasonCriticalProcess / RmRebootReasonCriticalService	a critical process or service uses the files
RmRebootReasonDetectedSelf	the installer itself uses the files

Services

using var session = InstallerRestartManager.CreateSession();
// Services are registered by their short name, stopping them needs administrator rights
session.RegisterServices("Spooler");
var affected = session.GetProcessesUsingResources();
Console.WriteLine($"Affected: {string.Join(", ", affected.Select(p => p.AppName))}");

RestartManagerApi has the raw P/Invoke declarations (RmStartSession, RmRegisterResources, RmGetList, RmShutdown, RmRestart, RmEndSession) if you need more control.

The example project Dapplo.Windows.Example.InstallerExample closes and restarts the FormsExample.

See also

• Power and system state
• Window messages and the SharedMessageWindow