Merge pull request #2128 from microsoft/user/dlopez/EnableSingleUseForToast2

Modify the CoRegister for Com Activation so if there are not notification handlers registered a new process will be launched every time

Author: David-Quero

dev/AppNotifications/AppNotificationManager.cpp

@@ -86,11 +86,14 @@ namespace winrt::Microsoft::Windows::AppNotifications::implementation
         {
             auto lock{ m_lock.lock_exclusive() };
             THROW_HR_IF_MSG(E_INVALIDARG, m_notificationComActivatorRegistration, "Already Registered for App Notifications!");
+
+            // Check if the caller has registered event handlers, if so the REGCLS_MULTIPLEUSE flag will cause COM to ensure that all activators
+            // are routed inproc, otherwise with REGCLS_MULTIPLEUSE COM will launch a new process of the Win32 app for each invocation.
             THROW_IF_FAILED(::CoRegisterClassObject(
                 AppModel::Identity::IsPackagedProcess() ? registeredClsid : winrt::guid(storedComActivatorString),
                 winrt::make<AppNotificationManagerFactory>().get(),
                 CLSCTX_LOCAL_SERVER,
-                REGCLS_MULTIPLEUSE,
+                m_notificationHandlers ? REGCLS_MULTIPLEUSE : REGCLS_SINGLEUSE,
                 &m_notificationComActivatorRegistration));
         }
     }