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Listing file in location

I'm a little stuck, as for this moment i don't have any code only an idea.
I was thinking to make a program in asp.net to list files within a location.
The file will probably be releases for programs and mods for gaming and stuff.
But i have searched everywhere to get files in a location. I could use system.io.fileinfo to list files in a directory.
But how to I get a Directory not in the solution but somehwere on the hard drive or even external storage server? The location i prefer not to be hard coded but selected by the user? any toughts on how a user can select a 'location' ?

In a console application, you could be doing something like this :
Ask for the path from the user with a readline.
Check if the path is correct / exists. (if not you could create it or display an error, also it could be a path with a file, you need to check if the path is to a directory or to a file)
Do the display of the files inside of the directory as intended.
We need more precisions if you want a better answer.

c#.net application which can opened while opening a folder

I would like to create a c# application which will open when i open a folder automatically.
My c# application is intended to be like a password system, so that the contents in the folder can only viewed after logging in to my application. Everything is ready..........
but i am confused how to open my application directly while opening the folder with a c# script?
I have now created a application which will ask the user for name and password while opening the application and now i want to make it open through the folder to be locked , how to do it?

Ok, first of all if you want the folder to be secure you should encrypt it otherwise all the user has to do to gain access is kill the process.
What i would recommend you do instead is create a encrypted file. For example a zip file. Then all you have to do associate the file with the program and to unpack it with the password. Then when the user is done delete it and overwrite the temporary folder. It's really important that you overwrite it otherwise the encryption is useless.
If you want to avoid conflict with other programs that work with zip files you can make your own file type it does not affect the content of the file in any way.
I hope this helps.

To make sure I understand... you want to build an application that will, when someone tries to open it, will only open after they supply a password. Hmmm... okay. A specific folder, or any folder? Local folders or folders on network shares? I initially was thinking a file system watcher approach, but that will only work on change events, like copying, renaming, deleting, etc. So that won't work. The closest would be to check last accessed time, but that is an alert ex post facto, so this must be rejected. I'm not sure how you could do this in C#. What is wrong with the robust security options MS has already established, like global groups. That provides flexible restrictions on access. Especially over large amounts of folders. Are users going to have one password per folder? Too cumbersome. One password per user? Use Windows authentication to lock it down. How is this app storing the passwords?
I recommend trying to leverage existing technology to solve problems before trying to re-invent the wheel. You have omitted the scope of this, and what you have already attempted, so we may not understand completely.

Why isn't my XML file being saved, even though the program sees the updated values next time I start it?

I'm reading the contents of an XML file and parsing that into an object model.
When I modify the values in the object model, then use the following code to save it back to the xml:
XElement optionXml = _panelElement.Elements("options").FirstOrDefault();
optionXml.SetAttributeValue("arming", value.ToString());
_document.Save(_fileName);
This works, as far as I can see, because when I close the application and restart it the values that I had saved are reflected in the object model next time I view it.
However, when I load the actual XML file, the values are still as they were originally.
Why is this? What do I need to do to save the actual XML file with the new values?

You are most likely experiencing file system virtualisation, which was introduced in Windows Vista.
Basically what this means is that you are saving your file, just not where you think you're saving it. For example, you might think that you are saving to C:\Program Files\Your App\yourFile.xml, but what is happening under the hood is that the OS is silently redirecting that to %APPDATA%\Your App\yourFile.xml. When you go to reload it, once again the OS silently redirects from that location.
This is a security measure designed to better encapsulate applications and their data and to prevent unauthorised writes to locations where damage can occur. You can still force a save to %PROGRAMFILES%\Your App, but to do that you either need to relax the ACLs applied to that folder, or you need to elevate the privilege level your application runs at.

I wasn't sure whether to put this as a comment or as an answer, but I think it could be a potential answer. It sounds like the XML file is being saved because the data is being persisted across instances of the application. It may be file system virtualization like slugster mentioned, but it might be a simple as the fact that you are looking at the wrong copy of the XML file. If you are using a relative path, the file may have been copied to the new location. I would suggest you do a quick file search for that file name and see what you get back.

It turns out the file was being copied to and read from the Output Directory. I can see that it's being updated as expected from there.

how to protect my files from editing in C#

I am new to C# , i wrote one application its contain directories and some file , i dont want to edit these file from outside of the program or manually , plz tell me how to do that if u provide the code that will be very usefull.
Thx

There is no real way to protect from within the application. If you're storing these files on a file system, they will be accesible based on file system permissions. You could store information in a password protected database or something similiar in order to make it only accessible to the application.
Actually on second thought, you may be able to save these files within a resource bundle. I'm not sure if that is entirely protected though.

You can set the read only attribute. It is only a minor inconvenience to someone who wants to edit a file, but you haven't got much control over what a user does outside of your program. At least if a user clears the read only attribute and changes your file you can blame them for it.
System.IO.File.SetAttributes("path\\file", FileAttributes.ReadOnly)

Are you just reading from these files or writing to them? If you're just reading them, you might embed them as resources in your compiled output rather than keeping them as files on disk.
http://support.microsoft.com/kb/319292

How do I programmatically check EFFECTIVE delete (modify) or write permissions in .NET?

Sorry in advance for the long question.
What I'm really interested in is a way to programmatically check if the executing windows identity has adequate windows privileges to write to a directory (or file) in an ASP.NET web services application. But I'll settle for retrieving effective delete (modify) privileges for a user for a given directory or file. The problem is that I would like to be able to do this without either writing temporary files OR necessarily performing the IO action and handling the exception.
Yes, there is a question on this already ( see How can I programmatically determine if I have write privileges using C# in .Net?)
Normally I would agree with the accepted answer that the best method is to just try the IO action and handle any exceptions -- System.IO methods do throw System.UnauthorizedAccessException to indicate failure as a result of privilege denial. But in the case of of UPLOADING files, I'd really like to check the privileges BEFORE wasting the time and resources of uploading the data since it is only AFTER upload that we can attempt to write the file or folder in question. I pity any users uploading a 2GB file over http only to be told after the upload completes that they don't have permissions to upload the file to the destination.
The usual approach to testing write access if you don't want to perform the actual write is to write a temporary file. The other question has an answer pointing this out. This is what our code currently does. BUT windows security allows write access without delete privileges. Users with ONLY write access but no delete end up leaving all sorts of undeleted .tmp files. And no, we don't want to use a Domain admin account to reset the ACL on the tmp files and then delete them. The approach I've been taking is to check if the user has write privileges using System.IO.Directory.GetAccessControl(..) or System.IO.File.GetAccessControl(..) and dealing with the various access rules and ACE returns... but with this I still have issues dealing with EFFECTIVE privileges -- i.e. in most cases I also have to look up the user's membership in any of the groups listed in the ACE that do have permissions on the object. There has to be an easier way.... doesn't there?

Well kudos for going the extra mile on user experience AND trying to maintain clean program structure. Maybe if you're uploading only you could try to create an empty 'placeholder' file with the same name as the final 2GB file will have, then just overwrite it. Not perfect since you could still end up with an empty file, but pretty easy and at least a little bit more elegant that some of the alternatives.

You could also have permanent file, say 'access_test.txt', which you try to overwrite with a datestamp or something to first to test the current access.