Should I use registry or a flat file to save a program's state?

We have a lot of products that are saving their "states" on the registry.

What is the best practi开发者_Go百科ce on saving program states? What are the advantages/disadvantages of saving program states as a registry entry or saving program states to a flat file such as XML?

Thanks!

The obvious awswer would be that storing those states in a normal file, makes it easier for users to backup/restore the state manually.

Also consider that the registry has some keys that are special for each user in the system.

I think registry is the best option to store user-specific information that can be discarded and recovered easily (eg, the last username used to login). Other data should be in a settings file that can be backed-up.

For years programmers had their app settings stored in config files. Then the times changed, and for years they used the registry instead - many of them used it badly, and it caused issues when Vista and its UAC came on the scene.

Nowadays, especially in the .Net world, Windows developers are moving back to storing stuff in config files again. Personally i think that is the best way, if you need to move your app to another machine, or reinstall your OS, all you have to make sure you do is save your config file to retain your settings.

There are things that you may still want to store in the registry though, such as (encrypted) licencing info. For everything else, config files are good. Do pay attention to UAC and file virtualisation though, so that you don't run in to trouble further down the track.

Personally I'd go for the flat file.

(I am assuming that "registry" means windows registry?)

A flat file allows you (or even the user) to inspect and eventually even modify manually the values. Depending on your situation this could be helpful for debugging, repairing mis-saved data etc.

Unless you thing you want to have the data to be "opaque" and therefore "hard to find/manipulate", the registry offers little in terms of benefits. Maybe it's faster, but if you have lots of state to save you better use an embedded DB instead of a flat file.

I used to follow Redmond doctrines. My programs used .INI files. Then I dutifully switched to the registry - and users started complaining. So, I bucked the trend and switched back to .INI files.

Some want to edit them (good/bad?). Some want to back them up, or transfer to a new machine. Some don't want to lose them if they reinstall windows.

AS a user, I have multiple partitions. Windows/programs/data/swap (and a few others). No programs go onto c:\program files, they all go into the programs partition. No data which I can control goes into c:\user data, it all goes into the data partition (use tweakui power toy, or regedit to change the defaults (but not all programs are well behaved and read the registry for those paths - some just hard code them)).

Bottom line - when Windows gets its panties in a fankle, I do a total re-insatll (approx every three months), and I format the C: drive.

By formatting the windows partition, I get a clean install. My data and programs are safe, though I may need to reinstall a few programs, which is why I go with portable versions where at all possible.

Imo, the registry is the biggest evil ever perpetrated on Windows - a single point of failure.

My advice? Locally stored config files. INI if the user is allowed to edit, serialized or binary format if not.

Or, you could offer a choice ...

Personally I go for a flat file, whether it's an INI file or XML file makes no difference to me. However in my line of work, we've had customers prefer the registry instead due to issues relating to deployment. It depends on who your client base is, and what the person keeping your product working prefers.

I always use regular files because its much easier to develop =)

Simple io vs I don't remember how read/write registry
Simple file copy/paste vs export/import keys for backup/developpement multiple versions of config for testing

Note that all of these advantages also translate into deployment strategies and generic client usage of the configurations

Depends how heavy deployment is. Most of my applications are XCopy-Deployable, that is they don't need an installer and can just be copied/unzipped. So I use .ini Files (using my own INI File Parser as .net has no built in one)

However, if your application needs to be centrally manageable (for example, using Windows Group Policies) or if you have a "heavy" installer anyway, the registry is the prime choice. This is because Applications that are installed normally to to C:\Program Files, and normal users do not have write access to this directory. Sure, there are Alternatives (%APPDATA% or Isolated Storage which has to be used when the Application is a Silverlight app), but you can as well "go with the flow".

Of course, if your application is supposed to run on Mono, you can rule out the Registry anyway and should go Flat Files.