I want to load a form in OnStart() method in my windows service; here is my code. It is not working. Can you please provide any help ?
protected override void OnStart(string[] args)
{
Form1 fr = new Form1();
fr.Show();
}
You can't use services that way. Services can't interact with desktop directly, because they run in another WindowsStation from the logged in users session. You need to create another application that will communicate with your service.
How to make communication you can read on MSDN and in this example. Some ideas also described already on StackOverflow.
Services run in a different window station and desktop to any interactive user. Even if the form is loaded successfully nobody will be able to see it.
You can set the "Allow service to interact with desktop" service option which allows a service to share the console's window station. However, this is a really bad idea. It opens up security holes and a host of other problems. E.g. what happens if there is more than one user logged in? Or if you're running terminal services?
A more conventional design is to have a client application handling the UI and talking to the service running in the background.
GUI requires Single-Threaded Apartment threading model. Forms require a message pump (like the one started by Application.Run).
A service is definitely not designed to show GUI (even interactive services are considered bad practice), it can be controlled from a GUI, though.
For a service to display a window it has to be marked as "Allow interaction with desktop". This can be done by the service installer or on the property page for that service.
That's not enough to get the window to display reliably, though. In practice you will have to determine if there is a user currently logged in and get their desktop. This is not a trivial undertaking and can be a source of security issues. If there is no one currently logged in, you are out of luck.
The best solution is to have a separate GUI app which talks to the service via some IPC mechanism.
Related
I need to display Message Box and Windows Forms through windows service by using c#. Anyone Please help me. Thanks in advance.
You cannot (easily) do this directly from the service's process. As descibed here, there is a way to create an interactive service, that is able to send/process windows messages and display windows.
But: Since Windows Vista, all services run in a separate user session, named "session 0". Thus, all windows displayed by services, are displayed in that session. It is theoretically possible (I have even done that once, just for fun), to switch to this session and view these windows, but this would hardly be of use in real life.
My advice would be to create a separate gui application (maybe one with a nice tray icon), that communicates with your service via e.g. TCP/IP or a database. This application can then handle any required user interaction and do the appropriate interaction with the service's process.
i am creating a window service. my requirement is to display window form from window NT service on particular interval. For testing purpose , i just want to display the form on service start:
protected override void OnStart(string[] args)
{
eventLog1.WriteEntry("In OnStart -before form show");
Messager_Form obj = new Messager_Form();
obj.Show();
// System.Diagnostics.Process.Start("calc.exe");
eventLog1.WriteEntry("In OnStart -after form show");
// timer1.Start();
}
it not working. Neither form is showing nor calc process is running. i have found some links
showing pop up , but most of them suggesting WCF. isn't it possible without wcf. can anybody show me the way to achieve this.
Cant be done*. In later Operating Systems that won't work as Windows Services are disallowed from interacting with the Desktop - instead UI presented by Windows Services is shown in Session 0, a special logon session which is not normally visible to the end user.
What you should instead do is write a separate Windows Forms application which is always running, but not always visible (possibly have that application run at startup and have an icon in the notification area) and communicates with the Windows Service using some form of IPC
When the Windows Service wishes to display some UI to the user it sends a message to the application, which in turns shows the desired UI to the end user.
*or at least it definitely shouldn't be done
I am just referring to the answer given in another link in StackOverflow
How to communicate with a windows service from an application that interacts with the desktop?
Answer is :
Be aware that if you are planning to eventually deploy on Windows Vista or Windows Server 2008, many ways that this can be done today will not work. This is because of the introduction of a new security feature called "Session 0 Isolation".
Most windows services have been moved to run in Session 0 now in order to properly isolate them from the rest of the system. An extension of this is that the first user to login to the system no longer is placed in Session #0, they are placed in Session 1. And hence, the isolation will break code that does certain types of communication between services and desktop applications.
The best way to write code today that will work on Vista and Server 2008 going forward when doing communication between services and applications is to use a proper cross-process API like RPC, Named Pipes, etc. Do not use SendMessage/PostMessage as that will fail under Session 0 Isolation.
http://www.microsoft.com/whdc/system/vista/services.mspx
Now, given your requirements, you are going to be in a bit of a pickle. For the cross-platform concerns, I'm not sure if Remoting would be supported. You may have to drop down and go all the way back to sockets: http://msdn.microsoft.com/en-us/library/system.net.sockets.aspx
Checking the "Interact with desktop" box will work on Windows NT, 2000, XP and 2003 but thanks to Session 0 Isolation that setting no longer works as you may expect in Windows Vista and beyond. You want to think very carefully before developing an interactive service...
I have a WCF service hosted in a Windows service.
This service the WCF have one metohd and in this method I have one important line :
Process Browser = Process.Start("iexplore.exe", hostUrl);
I install Windows service as local system, but when I'm trying to invoke that method, everything seems to execute, except that one important line... and IE didn't open.
I would like to add that the method itself is not in the service itself but in one of the service dll reference
Any idea why?
http://social.msdn.microsoft.com/forums/en-US/netfxbcl/thread/63a7d1ec-7077-489a-a250-f7422f04317b
" in order to get the service to actually show the UI, you'd have to set the service in Computer Management to allow it to interact with the desktop. In the services window in computer management, go to the properties of your service, and on the Log On tab, check "Allow service to interact with desktop" "
Since Windows Vista MS has been adding lots of security-related changed esp. in the area what Windows Services can/can't do. Anything "desktop-like" (printing, accessing network shares, using Office Interop etc.) is harder and harder to get working.
You should rethink your design since IMHO any "server-like process" (for example a WCF service) can be accessed in parallel by multiple requests and thus should NOT use processes which are NOT designed for this type of interaction... what happens if your webservice starts multiple IE instances that way ? Will IE behave as you need/expect it ?
IF you really really MUST do it this way you should have
a normal desktop process hosting the WCF service
OR
two processes, one your Windows Service and one running as a normal desktop process dealing with IE... these two process communicate via IPC
Under what user is the service running? Try running it under the currently logged in user, with privileges to interact with the desktop and see if that helps.
In general, its not a great idea to have services launching GUI processes. For example, what if no one is logged on. What if many people are logged on? Should it open in all sessions... etc. Have you considered exposing a simple (e.g. Net.NamedPipes) endpoint on your service, and writing a small client UI to interact with it?
I have an application, written by me in C#.net 2.0 - when the application is opened, a timer will check every 3 seconds for x. If x happens, it shows a warning in a windows form.
Is there a possibility to install this timer and the windows form call in a windows-service? So that the timer ticks every time a system is up and shows the message then?
No, it is not possible to have a service display a form. This is by design, since a service is supposed to run without a user interface
You can have a regular application that communicates with your service and displays the warning, but I don't know how exactly this is done.
IMO, you don't need a service, just create a regular application without a main form that runs in the background, performs your check, and displays a warning when necessary. You can add that application to the Run section of HKLM or HKCU, so that it is always started when a user logs on to the system.
Windows Forms cannot be displayed from a Windows Service. A Service runs only in the background.
You can have a separate Windows application that communicates with the Windows service and display warnings, information, etc.
To do this, the service runs on the LocalSystem account, and you have to enable the property for the service to interact with the desktop.
Services are forbidden from interacting with the desktop, including displaying windows or forms. In windows 2003 and XP you could work around the issue by marking the service 'interactive' and this would allow the service to display on the user session, but as of Windows 2008 and Vista this is enforced and services can no longer interact in any fashion with the user.
When services need to display anything, the solution is to split the logic into two separate processes, one being the service and one being a normal user process. The user process runs launched by the user, in its session (it can be launched automatically at session start up) and it connects to the service via some IPC channel (shared memory, named pipes, sockets etc). The service can then display anything it wishes to the user by asking the user process half of the application to display what it needs to display.
As others have said, remember that a windows service is supposed to be a background, never-interacting-with-the-user program. Many services run even when the user is not logged on -- how would they go about displaying a form when there's no desktop for them to display it on?
That said, it shounds like you're trying to shoehorn something into a service that shouldn't be a service. If you want something that runs in the background and still interacts with the user, look into making a lightweight system try application. In fact... here's a helpful tutorial:
Lightweight System Tray Application (NotifyIcon Based)
When should I go for a Windows Service and when should I go for a "Background Application" that runs in the notification area?
If I'm not wrong, my design decision would be, any app that needs to be running before the user logins to the computer should be a service. For everything else use a background app. Is my decision right?
Moreover, if I need "admin privileges" for my background app, I would escalate using a manifest. Are there any other specific advantage of running as a service?
My general rules of thumb are as follows
If it needs to always run, it's a service.
If it needs to be run under a particular user account, Network Service, Local System, generally it's a service (or a COM+ application)
If the user needs some control over it, it's generally a notification area application.
If it needs to notify the user of something, it's a notification area application
The fun comes when you have the need to run something as a system account, but also interact with it. IIS is a good example of this, it's a service, but the administration is an application - it needs to be running at the startup, it needs access to particular things a user can't normal access (c:\inetpub), but the user needs to be able to start, stop and configure it.
I would design an application as a service if the applcation has a critical purpose and should never (or rarely) be closed. Windows services provide good crash-recovery options, good notifications (see the recovery tab in service property).
Also a good reason to use services is because they can run under any user ( so if you
deploy them on a server that you remote to, you can safely log out after starting the service without worring that the application will close too).
I also design services in combination with a desktop application that can interact with the service and can be used to monitor or reconfigure the service while running. This way you can have all the benefits of a tray application, in your service.
However, you should not abuse using services and only use them, as I said, for cirtical applications.
I believe your decision is almost right, however, I would add one more condition. Take for example the mysqld service (you have a choice in this case, but most people run it as a service). It's ran as a service because you want to access the service anytime through potentially multiple applications. It's important that it is responsive to all applications calling upon it, and itself, is not much of anything, other than waiting to serve other applications.
Just something I would consider as well when making my decision.