How to check if file exists in a Windows Store App?

Question

Is there any other way of checking whether a file exists in a Windows Store app?

try
{
    var file = await ApplicationData.Current.LocalFolder.GetFileAsync("Test.xml");
    //no exception means file exists
}
catch (FileNotFoundException ex)
{ 
    //find out through exception 
}

Disposal

Answer 1

According to the accepted answer in this post, there is no other way at the moment. However, the File IO team is considering changing the the api so that it returns null instead of throwing an exception.

Quote from the linked post:

Currently the only way to check if a file exists is to catch the FileNotFoundException. As has been pointed out having an explicit check and the opening is a race condition and as such I don't expect there to be any file exists API's added. I believe the File IO team (I'm not on that team so I don't know for sure but this is what I've heard) is considering having this API return null instead of throwing if the file doesn't exist.

Gowk

I believe that the new IsAvailable property in Windows 8.1 addresses this. – Weisshorn

@Weisshorn - Thanks, that's good to know. I haven't had the chance to look into the 8.1 APIs yet. – Gowk

ApplicationData.Current.LocalFolder.TryGetItemAsync(fileName) can do the trick now. No more ugly exception handling required. Please remember that this is also an awaitable call. – Apteral

Unfortunately, that call doesn't exist for Windows Phone, so you're out of luck if you're building a Universal App for Windows 8.1/Windows Phone 8.1. I guess I'll just have to retarget my app to Windows 10.... – Pemberton

Answer 2

This may be old, but it looks like they've changed how they want you to approach this.

You're supposed to attempt to make the file, then back down if the file already exists. Here is the documentation on it. I'm updating this because this was the first result on my Google search for this problem.

So, in my case I want to open a file, or create it if it doesn't exist. What I do is create a file, and open it if it already exists. Like so:

save = await dir.CreateFileAsync(myFile, CreationCollisionOption.OpenIfExists);

Sailesh

This only works if you are trying to create file with a unique name. If you are just checking for existence of the file then obviously you wouldn't want to do this. – Compagnie

Answer 3

I stumbled on to this blog post by Shashank Yerramilli which provides a much better answer.

I have tested this for windows phone 8 and it works. Haven't tested it on windows store though

I am copying the answer here

For windows RT app:

public async Task<bool> isFilePresent(string fileName)
 {
    var item = await ApplicationData.Current.LocalFolder.TryGetItemAsync(fileName);
    return item != null;
 }

For Windows Phone 8

 public bool IsFilePresent(string fileName)
 {
     return System.IO.File.Exists(string.Format(@"{0}\{1}", ApplicationData.Current.LocalFolder.Path, fileName);
 }

Check if a file exists in Windows Phone 8 and WinRT without exception

Unpin

"The type or namespace name 'File' does not exist in the namespace 'System.IO' (are you missing an assembly reference?)" – Metalinguistic

What app type are you trying to use it in : Windows Phone 8, or Windows RT App? – Unpin

A universal Windows / Phone store app that targets 8.1. Also, while you're here: your WP8 function should just return a bool, and it doesn't need the async keyword either. – Metalinguistic

Thanks for letting me know about the correction, The 'File.Exists()' solution only works in Window phone 8. The 'localFolder.TryGetItem()' method will work in the Windows 8.1 part of the universal app. For windows phone 8.1 part: you can try the solution by Billdr https://mcmap.net/q/359238/-how-to-check-if-file-exists-in-a-windows-store-app. – Unpin

The answer you linked to wouldn't work, as it returns a file whether it exists or not (because it creates it in the latter case). – Metalinguistic

Its weird that they removed the File.Exists() from windows phone 8.1, I guess right now the only way is to try to open the file & catch an exception. – Unpin

Answer 4

You can use the old Win32 call like this to test if directory exist or not:

GetFileAttributesExW(path, GetFileExInfoStandard, &info);

return (info.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) ? false: true;

It works in Desktop and Metro apps: http://msdn.microsoft.com/en-us/library/windows/desktop/aa364946%28v=vs.85%29.aspx

Apteryx

Where does FILE_ATTRIBUTE_DIRECTORY come from here? I tested this function, and it works, but I don't see how. Thanks! – Crites

Answer 5

Microsoft has added a new function to StorageFile in Windows 8.1 to allow user engineers to determine if a file can be accessed: IsAvailable

Weisshorn

Not supported on Windows *Phone* 8.1, only Windows 8.1. I don't know what MS is playing at. – Compass

Answer 6

The other means to check is by getting files in local folder

    var collection =  ApplicationData.Current.LocalFolder.GetFilesAsync() 

Using this method and then iterating over all the elements in the collection and check for its availability.

Jetport

Please check your caps lock key. – Duet

Answer 7

I tried to write my own using old tricks:

1. GetFileAttributesEx() always seems to end up with ERROR_ACCESS_DENIED if file selected via FileOpenPicker;
2. Ditto for FindFirstFileEx();
3. _stat() always ends up with ENOENT when file selected via FileOpenPicker;
4. CreateFile2() with CREATE_NEW option works -- if file does exist it will fail with INVALID_HANDLE_VALUE return value and ERROR_FILE_EXISTS last error; if file does not exist you have to remember to delete created file afterwards.

All in all -- you're better of sticking with exception handling method.

Dannydannye

Answer 8

8.1 got something like this, I tried it worked.

var folder = ApplicationData.Current.LocalFolder;
var file = await folder.TryGetItemAsync("mytext.txt") as IStorageFile;

if (file == null)
{
   //do what you want
}
else
{
   //do what you want
}

http://marcominerva.wordpress.com/2013/11/19/how-to-check-if-a-file-exists-in-a-windows-8-1-store-apps-no-more-exception-handling/

Offense

While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. – Decadent

Answer 9

    Dim myPath As StorageFolder
    If (From i In Await KnownFolders.MusicLibrary.GetFoldersAsync() Where i.Name = "PodBong").Count = 1 Then
        myPath = Await KnownFolders.MusicLibrary.GetFolderAsync("PodBong")
    Else
        myPath = Await KnownFolders.MusicLibrary.CreateFolderAsync("PodBong")

    End If

Dannica

This code will check for folder with out using and exception. – Dannica

Answer 10

The documentation for TryGetItemAsync says, "This example shows how to checkfor the existence of a file." It seems that this API is officially intended to serve that purpose.

Leisha