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UWP Enumerate Folders with 10,000 files while creating a subfolder

I'm a fairly experienced developer, but this has me stumped in UWP - I'll keep it simple.
Let's say I want to go through all photos in the pictures folder, watermark them, and save the watermarked version in a sub folder of pictures (eg. pictures\watermarked)
Sound easy?
Try 1: Using GetFilesAsync (incl. GetItemsAsync, GetFoldersAsync) - This method goes through every file, giving me the StorageFile objects I need.
There are 2 problems with this approach:
I can't show a progress bar until I've scanned every file and that's
painfully slow in UWP.
The Runtime Broker will consume all memory if I keep any reference
to the StorageFile object (so enumerate and enumerate again to get a
progress is seriously slow, think 1,000 times slower than Win32)
Try 2: Using Queries - This method involves using Windows.System.Search & Queries to return a list of pointers (ish) to all the files. I can then use StorageFolderQueryResult to get each StorageFile on the fly and release immediately so that the Runtime Broker behaves. This is very fast as it uses the Windows Index system, really, really fast.
The problem is that the query system is fairly stupid, as soon I create the subfolder "Watermarked Photos", the storagefiles returned by the Query (which did not exist when it was queried) start to contain files from the Watermarked folder. It appears that the Query is actually just a number of files, not a static list of the actual files, so the results are arbitrary based on any files added/removed after the query was invoked within it's scope.
Anyone with thoughts on how to do this?

RESOLVED - It's not possible using the index system. I created my own Query class. It uses the GetItemsAsync method of folders, the number of objects here won't kill the RuntimeBroker, I store the Path in a string list. containing the paths of all files and sub folders. I can then use GetFileFromPathAsync to instantiate and destroy StorageItems as needed. The RuntimeBroker is okay with that, although it's not the best performance it does give me custom file/folder filtering. Happy to elaborate if anyone needs more info.

Best way to track files being moved (possibly between disks), VB.NET (or C#)

I am developing a "dynamic shortcutting" application which creates special shortcut files which point to a registry entry rather than an actual file/executable. The registry entry contains the path of the desired file. I want to have a daemon running which watches the linked-to files and updates their registry entries if they are moved or renamed. Renamed I can handle using System.IO.FileSystemWatcher, but what is the best way to handle moved files?
I know this is beyond the basic functions of FSW (despite being a low-level file-system operation). The question is, what is the best way of doing it?
Most posts/articles I have read suggest ways that feel altogether "hacky", which basically involve looking for a delete followed by a create in a new place of a file, and connecting the two by file size, meta-data, time between the delete/create triggers, hashes, etc. This may well be the method I have to resort to, setting up FSWs on all drives. However, I am hoping there might be a better way.
Is it possible to either:
2.1. Listen in to the shell and "hear" move operations?
2.2 Or (even more radical) replace or add something to the shell move operation that either triggers some sort of event or performs the registry-updating task itself, precluding the need for the daemon?
I have a feeling that everyone is going to tell me that 1. is the only course, but I look forward to your suggestions. (answers in VB.NET preferred, but can translate from C# if necessary).

[I'm not sure if this should be appended as an "update" to my original post or posted as a separate answer]
To sum up (all two of) the answers plus my own experimenting (to try to give a definitive answer to this question):
It seems the only high-level (.NET) solution is to use the FileSystemWatcher which does not detect "move" out-of-the-box (despite it being a low-level command). The FSW approach is non-trivial, comparably resource-expensive, sloppy in places (i.e. using timers) and has its limitations and caveats. Nor does it provide a true reflection of "move" - it merely infers it from symptoms that are very likely to be a move (and have the same effect on the file-system in any case) but could theoretically be produced by non-move actions. Also, it appears you have to know what files you want to watch for moves in advance of the move happening, there's no-way of telling as it occurs.
On a lower-level (which would involve C++), one could hook API calls to get a faithful picture of when "moves" are called. This has the advantage that you don't have to decide to watch files in advance, and is also less resource-expensive than listening to "deletes" and "creates" and trying to compare them.
On a systems-programming level (which would involve C++ and could easily break your computer if you didn't know what you were doing) one could build a filesystem filter driver: this would take the concept of detecting moves to a truly anal level, detecting re-allocation of filesystem resources performed even without the kernel.
After some experimenting, here is the general structure of how the FileSystemWatcher approach (or at least the most obvious one to me) works, its quirks and its limitations. [no code atm, it's all pretty integrated into my application and I'm yet to optimise it, but I might add some snippets in here later].
The FileSystemWatcher method (to detect when files are moved or renamed):
.1. FileSystemWatchers.
You will need to create one FSW for each highest-level directory you want to monitor (for example, one for each writable logical drive).
.2. Renamed.
Straightforward renaming of the file is trivially handled.
.3. Moved.
This part is very far from trivial; it basically involves comparing files in three different scenarios.
3.0.1. Deciding if a deleted/moved-from file is the same as a created/moved-to file.
For determining whether a deleted and a created file are a match, filename is useless (can be changed during a move). You could use a mixture of file size and attributes like time created, or even a hash of the entire file. In my particular solution I only needed to watch the movement of specific files "registered" before load-time, so I was able to give these files a unique fingerprint as metadata that I could then use to compare files (this works fine in real-world scenarios, but is easy to break maliciously in testing, which disappoints me as a perfectionist.)
3.0.1.1. When to read filesize/attributes/take hash?
Before I came up with the static fingerprint idea, I was testing my code with a simple filesize + creation date validation check. I quickly realised though that I had to have a note of the filesize and creation date (or hash or whatever else you want to use) of the deleted file BEFORE it signals as "deleted", because you can't check the size of a file that doesn't exist. If (like me) you know the files you want to watch in advance, then you need to read in those values before you enable the FileSystemWatchers; you also need to listen for "change" events on those files to update the values of filesize and creation date, take a new hash etc. This then begs the question: what do you do if you DON'T know what files you are interested in watching to see if they move? What if you only know you are possibly interested in knowing if they've moved when they "delete"? That, unfortunately, is beyond me (it wasn't something I had to deal with.) Unless you can come up with a solution to this problem, there is zero point in continuing with the FileSystemWatcher approach. Furthermore, I would conjecture (though could very easily be wrong) that there is no high-level solution that will meet your needs. If you do however come up with a solution (please post it below/comment on this post/edit it in here on this post), I have made the rest of this compatible.
3.1. Scenario 1: Direct moving of the file itself.
Upon the "delete" of a specific file being detected, you need to start listening for a "create" of a congruous file. Rather than listening indefinitely for the matching "create" of a file that might just have been deleted (which in reality involves inspecting every file created in the directory), you can use a timer to start and stop a "listening" flag (practical, but from a purist point of view a little arbitrary), deciding that after e.g. 1000ms with no appropriately matching create it's likely there won't be one.
3.2.0. A common misconception.
A lot of people seem to be under the impression, after glancing at the docs, that moving or renaming a folder triggers a rename for all their subfiles and subfolders rather than a delete and a create. In actual fact what the docs say is:
If you cut and paste a folder with files into a folder being watched, the FileSystemWatcher object reports only the folder as new, but not its contents because they are essentially only renamed.
(i.e. only the top folder throws rename or create/delete and the subfiles/subfolders throw NOTHING). Meaning if you want to know when and where a certain file is moved, you have to listen out for each and every of its ascendent folders as well.
3.2.1. Scenario 2: Renaming of a containing folder.
In my solution, because I knew all the files I was watching, whenever one of my FileSystemWatchers reported a rename of a folder rather than a file (the portion of the string after the last "/" will contain no ".") I checked each of my watched files to see if their paths were in that directory and if so, changed the beginning of the filepath to the path of the new directory et voila!, I knew where my files had been moved to. If you do not now in advance what files you are looking for, then you will have to recursively search through everything in every folder that throws a "rename".
3.2.2. Scenario 3: Moving of a containing folder.
This one feels like a slap in the face: in order to build your move-detection routine, you have to be able to detect moves. Here folders will throw a "delete" followed by a "create". In my case the solution just recycles the techniques in 3.1 and 3.2.1: when a folder "delete" is detected, I check to see if it contains any of my watched files. If it does, I set a "listen" flag (and a timer to snuff it) and check the subdirectory path of my file in the old folder against every new folder "create" that is detected to see if it points to a file with the desired fingerprint. If it does, I now have the old and new paths of the file and have detected the move. If you don't know what files to watch for, you may have to validate folder moves by comparing size on disk and number of subfiles/subfolders between "deleted" folder and "created" folders to confirm a folder has moved first, then search the folder recursively for the files you're interested in.
3.3. FURTHER COMPLICATION: Cross-drive moving of large files.
This is a problem I fortunately didn't run into (because I was only comparing fingerprint metadata, and didn't need access to files); however moving large files between drives (which transfer in stages, triggering a create event then a series of change events) can cause real headaches.
3.3.1. Headache 1: The "create" fires when the destination file is incomplete.
This means comparing its size to a "deleted" file will produce a false negative. You can't even take a hash of the first part of the file to indicate to your program that this "might" be the deleted file, because the move operation will have the file access permissions locked down. You just have to try and tell if the created file might still be moving and wait for it to finish.
3.3.2. Headache 2: No sure way to "tell" that the created file is still being moved.
Some have suggested checking the file access permissions on the created file, but they might be indistinguishable from those on a file created and still in use by any random application. Others have suggested setting short time-limited listen flags for "changes" on the file, but again this is indistinguishable from a file being modified by an application. In fact if the file happened to be a log file constantly and rapidly being updated by some process, then waiting for "changes" to the file to timeout might never end.
3.3.3. Headache 3: (UNTESTED) possibly these sort of moves "delete" the file after "creating" the destination file*.
It makes sense that this would be the case, though I haven't tested it. [if anyone does know, feel free to edit (or delete) this section appropriately]
3.4. A philosophical quandry: are two identical files the same?
This is a very pedantic and arbitrary thought-experiment, but say you have two drives, each with an identical copy of File.txt. You run a batch file that deletes the copy on the first drive then immediately makes a copy of the file on the second drive into the same folder on the second drive and names it Copy of File.txt. Unless you are using fingerprints, your code will identify a delete and then a create of an identical file and be unable to distinguish what happened from a move (with renaming) of the file from the first drive to the second. The final state of the filesystem is identical in both cases so it shouldn't cause your application to behave unexpectedly, but art thou really content to call that a "move" based purely on isomorphism? (especially when you know the kernel sees it differently)?

Using high-level unrestricted api provided by C# - no, you cant. Use FileSystemWatcher.. On same drive operation of moving file is not "delete and create" - it's "rename".
If you can/want to go into lower-level, then you can hook MoveItem and MoveItems of IFileOperation shell's interface, and MoveFile from Kernel32.dll... It will work with most of apps, but require expansion for security rights for your application, that mostly unacceptable in corporative environment..

The task has two flaws that make it hard to implement: (a) move operation across the disks is actually a sequence of read/write operations followed by deletion rather than move. And during those read/write operations there can be some transformation of data in place ; and (b) moving can be performed not by just a shell.
What you can do is employ a filesystem filter driver to intercept file operations right when they take place. Then you need to detect the sequence of read and write operations performed by the same process over your file. I.e. if your code detects, that the file is read sequentially (NOTE: some copying tools can read the file in multiple threads in parallel) and then write similar blocks of data to the other file AND after reading everything the source file is deleted AND the complete file contents have been written to the other place, then you can guess that you have come over file move operation.

Bump & update: This may well be against the rules of StackOverflow, but I would like to point out to the many people landing on this page (and the myriad similar questions on SO) that I have started a feature request on MicroSoft UserVoice to add MOVE detection to FileSystemWatcher. The best solution in the long term, rather than trying to work around the problem, might be to petition MicroSoft to fix it. If you have come here because you too need a solution to this problem, please consider clicking here and voting for this feature.

Is it considered good/acceptable practice to save a file in the temporary directory?

I am developing a WinForms application using C# 3.5. I have a requirement to save a file on a temporary basis. Let's just say, for arguments sake, that's it's for a short duration of time while the user is viewing a particular tab on the app. After the user navigates away from the tab I am free to delete this file. Each time the user navigates to the tab(which is typically only done once), the file will be created(using a GUID name).
To get to my question - is it considered good practice to save a file to the temp directory? I'll be using the following logic:
Path.GetTempFileName();
My intention would be to create the file and leave it without deleting it. I'm going to assume here that the Windows OS cleans up the temp directory at some interval based on % of available space remaining.
Note: I had considered using the IsolatedStorage option to create the file and manually delete the file when I was finished using it i.e. when the user navigates away from the tab. However, it's not going so well as I have a requirement to get the Absolute or Relative path to the file and this does not appear to be an straight-forward/safe chore when interacting with IsolatedStorage. My opinion is that it's just not designed to allow
this.

I write temp files quite frequently. In my humble opionion the key is to clean up after one self by deleting unneeded temp files.

In my opinion, it's a better practice to actually delete the temporary files when you don't need them. Consider the following remarks from Path.GetTempFileName() Method:
The GetTempFileName method will raise an IOException if it is used to
create more than 65535 files without deleting previous temporary
files.
The GetTempFileName method will raise an IOException if no
unique temporary file name is available. To resolve this error, delete
all unneeded temporary files.
Also, you should beaware about the following hotfix for Windows 7 and Windows Server 2008 R2.

Creating temp files in the temp directory is fine. It is considered good practice to clean up any temporary file when you are done using it.
Remember that temp files shouldn't persist any data you need on a long term basis (defined as across user sessions). Exaples of data needed "long term" are user settings or a saved data file.

Go ahead and save there, but clean up when you're done (closing the program). Keeping them until the end also allows re-use.

Periodically finding changed files in a directory using .NET

I'm trying to find the most reliable way of finding new and modified files in a directory using C# and .NET. I'm not looking for a real time solution, I want to check for changes at given times. It could be every 5 minutes or every hour etc.
We have CreationTime and LastWriteTime on the FileInfo object, and this seems to be enough to get new and modified files. But if a file is renamed none of the available dates are changed and the file will be missed if we just look at CreationTime and LastWriteTime.
At the moment i'm maintaining af "snapshot" of the files in the directory including the time of the last check for changes. This enables me to compare all the files in the directory with files in the snapshot, if the snapshot is missing a file it is either new or renamed.
Is this the only way? Rr am I missing something. I'm not going to use FileSystemWatcher as it seems pretty "buggy" and is required to run all the time.
Any suggestions are very welcome.
Merry Christmas!

Use the FileSystemWatcher class, it's the good way. Maybe you could be more specific with the
as it seems pretty "buggy"
EDIT: FileSystemWatcher does support renaming events.

The Microsoft Sync Framework has components for synchronising files.
The framework covers all data types and data storage and the file system component should be more reliable than the FileSystemWatcher. As it says in the MSDN:
It can be used to synchronize files and folders in NTFS, FAT, or SMB file systems. The directories to synchronize can be local or remote; they do not have to be of the same file system. An application can use static filters to exclude or include files either by listing them explicitly or by using wildcard characters (such as *.txt). Or the application can set filters that exclude whole subfolders. An application can also register to receive notification of file synchronization progress
I know you really only want to know when files have changed, but given that you've already dismissed the FileSystemWatcher route it might be the only reliable route (other than doing what you are in maintaining a snapshot yourself).

Your problem looks very much like a Database with no primary key.
If you asssign, say, a GUID to each file in that folder and check for that GUID instead of the filename, your application will be much more reliable.
So that's the theory, in practice, we're talking metadata. Depending on your system, and the files contained in that folder, you could use Alternate Data Streams.
Here is a SO question about it.
It boils down to having information on a file that is not stored within the file, it is merely linked to it.
You can then look it up in a DOS box:
notepade.exe myfile.txt:MYGUID
It requires the system to use NTFS.
HTH.

A very primitive approach would use a command of "dir" and comparing outputs...
Here is some info on params:
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/dir.mspx?mfr=true
Along with you snapshot of dates, you can compare the outputs of dir... its very fast and low on resources consuming...

File system watcher class in .net provides two methods:-
OnChanged
OnRenamed
You can set the EnableRaisingEvents to true and that is!!!! Every thing is simple with Dot Net chill!!!

Getting number of files in a partition

I wrote a code in C++ CLI which can loop through all files in the system. I want to know the number of files are existing in the system programmatically without counting the files one by one!
Also...Would that number be useful in scanning progress bar?

If you are using NTFS, you can call the FSCTL_GET_NTFS_VOLUME_DATA IoControl to get a whole bunch of data for your volume. The number of files will be at most MftValidDataLength / BytesPerFileRecordSegment. Keep in mind that this is a maximum number of files that can be on the volume, so the actual number will always be less.
I would also hope that you'd be using FSCTL_ENUM_USN_DATA to read the files rather than walking the directory tree (which is inaccurate and error-prone). This thread has an example of somebody doing it in C#: http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/c1550294-d121-4511-ac32-31551497f64e/

That would depend highly on the filesystem in use (and the administrative privileges held by the impersonated user :))
You might find something here or you can enhance your question with more details