Windows Services - Is it advisable to update its config file while running? - c#

As per my title, I would like to clarify: Is it advisable to update the config file while a .Net windows service is running?
What would be its implications, if this is possible?
Thank you.
Cheers,
Ann

There are other excellent answers here, but what are you asking? Are you asking about a service that you are writing? Or about someone else's Service.
If it is about a service you are going to write, then no, there is no automatic reload of the .config file when it is changed. You will either have to:
Restart the service to see the changes.
Write your service to use a FileSystemWatcher to see if the config file has been changed and then decide what you want to do with any or all the values that have changed.
If it is about someone else's service, you will need to ask them how it works based upon the above description.

This should have no effect on the running program. Configuration is loaded during application startup. If you want those new settings to take effect, you need to restart the service.
Edit:
More to the point of answering your question: When one creates a Windows service in .NET (I'm using Visual Studio 2010), an application configuration file is not created with it by default. By adding a New Item / Application Configuration File (App.config), you are creating a file that gets loaded at the start of the service. As commented below, there is no guarantee that it isn't being monitored during run time (unless you're the creator and you know that's the case), but this is not the common practice for App.config.
Under these standard conditions, it is advisable to make the changes, while running, after backing up the working copy of the config file. Then restart the service. If you broke it, revert back to your working copy.

You can do it but it comes with a cost,
do you want your service poll to know if there is any changes to the config file while it is running ?
Generally, I would not recommend polling for the content changes in the config file.

Related

Is it bad practice to programmatically update the web.config?

I've built an installer that creates a website, application pool, and then assigns the website to the app pool. As part of this I allow the user to input different settings for various connection strings (allows the developer to set them to DEV / UAT etc.). I then modify the web.config with the settings input by the user.
As this is something that will only be installed by a small bunch of developers I'm not concerned with the security of the input (I'm aware they could put in anything), but more with whether it's considered bad practice to modify the web.config in this way?
I've read a few questions on here regarding how people do this and generally in each one there is someone saying that it's not a good idea to do this. The second answer on this question states that doing so will restart your application. I can see how this could cause problems if your user is in the middle of using the app, but for my scenario this isn't relevant. Is this the only reason to consider when doing this?
The warnings are usually applied when someone is talking about having an asp.net website update its own web.config file. But as I understand it, you're talking about updating it from your installer, and this happens before the site is used, so it should be fine.
And, of course, think about it the other way - what's your alternative to manipulating these files programmatically? Do you have any means at your disposal for manipulating these files that doesn't, at some point, have some program open the file and write to it?
Notepad? It's a program.
IIS Manager? It's a program.
Your installer? It's a program.
web.config is like the .htaccess file, in wordpress some plugins automatically updates these files accordingly.
This links might help you, I did have this same question the other day
Change a web.config programmatically with C# (.NET)
Just a (perhaps obvious) thought: Be careful not to overwrite any manual changes added after the installation.
If I had made some custom changes to a config file, I would not want them to be overwritten by a program. It does not sound as if this would happen in your scenario though, so if the solution works for you, I can't see any real problem.

log4net disable question

I am currently coding a very large project, I am near the end of the development stage and have sent out an evaluation version to the consumer so he can check for bugs and what not.
He told me that there was a large log file being created every time the application starts up.
After some investigation I found out that the log file was created using log4net via an external DLL which I use in my application.
I have searched a bit and found you can disable log4net logs through an app.config file and adding several values there, I tried this but with no success, the logs are being created no matter which value I use in the xml config file.
I have no access to the external DLL source code and I have searched for an xml configuration file that the DLL uses - but have not found anything.
I would like to disable log4net completely, the Logs are pretty useless for me since I use my own log engine, which i can configure any way I want it.
Thanks for any help
When you call for log4net you can specify the config file.
check the log4net initialization in your app to see where it gets the instructions.
another way is to configure log4net to use windows event log rather than a file and configure a limit on the log size.
You can specify the config file that log4Net uses; by default it is named log4net.config
If that's not the case, I would suggest firing up Process Monitor to check which file it is using.
[BTW, I would be slightly curious about using a third-party DLL that I didn't have control over.]
Log4net can also be configured programmatically. I wonder if the dll is doing that? If the dll is configuring log4net programmatically maybe you could use the log4net api to turn it off. I don't have a good example of how to do that now because I am on my phone.

Automatic update

I have a system with two web applications, one web service, one Windows service and a WPF application running 24 hours a day on a touch screen. All of them are connected to a database.
I want to be able to upgrade all of those applications by uploading upgrade files to the database and set the date and time for the upgrade to occur.
I have one idea on how to do this.
An application has a thread running to look for available upgrades.
When an upgrade is found, the file is downloaded to the application's computer.
When download is complete, the applications triggers a restart.
When application starts, it looks for an upgrade file on the local computer.
If upgrade is available, the application upgrades itself.
I'm not really sure how all these steps should be done yet, especially the last one. But I want some comments about this. Is this completely wrong? Am I on the right track? Any tips on how to do it like this or in another way?
I think you're going down the right lines here. A polling application to check the database for the existence of a new update followed by an xcopy deployment script would do it.
This might be doable from a PowerShell script too, that runs on a schedule, say every 10 minutes. It could check the database, close the process and service, xcopy the application (from a shared source) and restart the said service and app.
All this assumes that you are not using Windows Installer to package and deploy your application initially. Although an xcopy to directly replace binaries wouldn't hurt an MSI package, it's not recommended. We use AD MSI deployment at work and it's a pain at the best of times!
MSDN contains references for MSI vs XCopy deployment for WPF applications (as well as the security requirements).
This was the first link I found for querying SQL from PowerShell: http://elegantcode.com/2008/03/27/discovering-windows-powershell/
Good luck!
You will have trouble doing this with ClickOnce. ClickOnce would only work for your WPF app, it can't do anything with the services or web application. You could write a separate ClickOnce-deployed "Updater" app whose job is to update the other apps, but that still seems a little iffy.
It may sound stupid, but I'd start with the simplest thing I could think of. How about using Dropbox to push your update files; then an AutoHotKey script that runs on startup, watches the Dropbox folder for new updates, and runs them?
Sounds hokey, but it's something you could prove out in an hour or two.
Microsoft have an Updater Application Block which might be what you are looking for.
Do you really want to run an update from the database or is this just a possible solution? You are reinventing the wheel.
Have a look at ClickOnce deployment, everything you need is already done for you and integrated into VisualStudio. If you use something that already exists you have the benefit of existing documentation, helpful blogs of people who have already gone through the pain points and updates and fixes.
ClickOnce Deployment
ClickOnce Deployment in .NET Framework 2.0
How you want to use ClickOnce depends on what you want to get out of it. Out of the box you can very easily create a deployment that checks for an upgrade every time you run the application but you can also with a little bit of code have the application check for updates whilst it is running.
The Updater Application BlockVersion that Dominic Zukiewicz mentioned is the pre cursor to ClickOnce.
EDIT
ClickOnce provides a roll-back scenario on both the Server and Client end. The client can roll back to a previous version using the normal add remove programs dialogue and you can easily republish a previous version.
You could create another Windows Service that does the updates on a daily basis. The service would look on a specific folder if there are any updates to be process. For example it could look for an xml file which tells it the new version of the application and what the files to update are. It would shut down the application/services, backup the files that it needs to update, start the application/services, and clean up backup files keeping at least three backup files. The service should keep track of the last and current version installed so that when it reads the xml file it can check if it is a new update or not or you can simply delete the xml file when it completes.
How about Google Omaha? It's an open source tool, currently used to push updates of Google Chrome and Google Earth. Omaha can handle application installation, too. A high-level design overview can be found here.

single exe with changeable settings

I am trying to make a simple application which will be used to point a web browser control to some of our web applications at my work. I would like to have only one exe file but also have an admin window to change some of the settings and have them persist when the application is closed. Is that possible? I have looked at the application settings resources part but as I understand that makes a file that loads the settings.
I don't want to have to parse a file or have anything but ONE file so please don't suggest doing that if it is possible.
Just use application settings - that will create a single file, you won't have to do any parsing, it'll all be fine.
It'll be separate to the exe file, but unless you meant that "ONE file" to include the executable and rewrite that on the fly, it should fit your description easily.
For example, let's build a console app that just remembers how many times it's been launched:
Create a new console application project
Go to the properties page, and click into the Settings tab.
Click on the link to create a settings file
Type in the table to create a setting called "LaunchCount" of type int. Make it either user scope or application scope, depending on whether you want it to be persisted per user or system-wide.
Hit Ctrl-S to save.
In the Main method in Program.cs, write this code:
Settings settings = Settings.Default;
settings.LaunchCount++;
Console.WriteLine("Launch count: {0}", settings.LaunchCount);
settings.Save();
Add the appropriate using directive for Settings (put the cursor in Settings and hit Ctrl-.)
Run the app several times, and observe the number increasing.
You can't have persisted settings without having a separate file...safely. You must either have a separate file, which is the standard and suggested approach approach, like the one created with Application settings, or you must use something like the registry to save settings.
Keep in mind, though, that using the registry is highly discouraged due to security reasons. Plus most companies don't allow access to registries anyway which means that anyone without this access could not use the settings feature.
There are several ways to do this. You can use a command-line argument to do that. Launch the app from the shell and put in your command line argument and change how it launches.
A UNIX-y approach is to look at the name of the exe and change behavior based on that. If I recall correctly, rsh and rlogin are the same executable - they just look at argv[0] to decide how to run. In windows, this is straight forward - look at System.Environment.GetCommandLineArgs - if there is a non-empty string in the 0th element of that, it will be your executable name.
For persisting settings, see Jon Skeet's answer.
I have to say that this is generally a bad idea, but I've done this before a long time ago in VB6. I created a Resource within the exe and then (somehow) directly manipulated it.
The problem is, is that this is usually not possible within the .NET framework due to it being memory resident. These guys tryed it out in .net and they ended up creating an program in IL to do the heavy lifting... Modify Emdeded String in C# compiled exe
Go with a settings file as Jon suggested!

Generating the App.Config file for a Managed Windows Service using WCF

My next project is going to be using Windows Communication Foundation to host Managed Windows Services, so I have been trying to follow a HOWTO on msdn - How to: Host a WCF Service in a Managed Windows Service. Sounds like a perfect match.
All was well until it started mentioning an App.Config file but without outlining how it got generated in the first place.
As I have posted there, there is probably some assumed prior knowledge (perhaps from another tutorial), but I couldn't find the answer after some searching.
Thanks in advance.
Are you talking about item #5? The app.config file is generated by you. You can add the item to your project in VS.NET by right clicking on the project and selecting to add a new config file. Then you can add the section as indicated by the step.

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