how to delete files on internal or external storage in Maui:Andorid

john murray 11

I have seen a couple of posts related to this and it happens on Xamarin Forms similarly

1) open a file picker
2) read file process data
3) delete file

   var res = await PickAndShowAsync(opt);  
           if (res == "") //user cancelled the file picker  
           { return; }  
           doprocess(dbpath);   // this opens file reads and processes data closes file; - successfully  


    if (File.Exists(cdbpath))      // dbpath is fully qualified folder and filename usually file is on attached usb sd card reader   
                                             // but I have set up a similar arrangement picking file from internal storage   
                       {  
                         var fh =   File.Open(csvorig,FileMode.Open);  
                           fh.Close( );  
                             try{  
                             File.Delete(fbpath);  
                            }catch(Exception ee)        never catches any exception but does not delete the file  
                           {  await DisplayAlert("warn",ee.Message,"cancel")}

Unfortunately it takes the directive File.Delete(myfile) but does not delete NOR does it throw any exceptions
I have tried File.Exists - returns true as well as opening and closing the file (obviously it is opened for reading and data processing but it is closed before attempting to delete

NOTE the windows version of this deletes files happily, the Android versions do not
Yes of course the permissions are set READ_EXTERNAL WRITE_EXTERNAL READ_INTERNAL etc etc

I can see from 1 post that others have experienced this issue but the proposed answers involve Android context calls and elaborate code requesting permissions which cause huge numbers of errors or using a dependency interface which MSDN docs say should be necessary

the manifest is as follows

   <application android:allowBackup="true" android:icon="@mipmap/appicon" android:roundIcon="@mipmap/appicon_round" android:supportsRtl="true"></application>  
   <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />  
   <uses-permission android:name="android.permission.INTERNET" />  
     <uses-permission android:name="android.permission.READ_INTERNAL_STORAGE" />>  
           <uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" />  
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />  
     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />  
     <uses-permission android:name="android.permission.MANAGE_USB" />  
     <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />  
     <uses-permission android:name="android.permission.USE_CREDENTIALS" />

I would be very grateful if anyone can point me to an answer - I am returning to use Maui after using Xamarin some years ago and I cant get my head around how complex its become

Alessandro Caliaro 4,181 Reputation points

2022-07-02T19:54:26.14+00:00

which is the android version? Starting from A10 is difficult to work with external storage, and "impossible" from A11
john murray 11 Reputation points

2022-07-03T09:06:12.377+00:00

thanks Alessandro
its targeting And 10 using sdk 29
Ive picked up that something had changed with Android 10 and above I notice that there is another manifest setting
<application android:requestLegacyExternalStorage="true" ... >
but that makes not difference
Is there ANY way one can move or delete a file on external storage in Android >10? I have a 3rd party app fielmanager ++ which seems to happily delete files anywhere - hows that done ?

finally in many places on the web examples are shown of this syntax for dot net but it doesnt work
File fhand = new File(mypath) ;
fhand.Delete();

Any Ideas on that?

FWIW I'm running 2022 VS preview 17.3 preview 2 xamarin.android 12.3.99.95
Alessandro Caliaro 4,181 Reputation points

2022-07-03T11:12:38.407+00:00

It's strange that you can delete a file in A10 with reauestLEgacyExternalStorage set to true. Take a look to maui issues if there is something open about this problem.

for A11, you should use MANAGE_EXTERNAL_STORAGE permission manage-all-files
john murray 11 Reputation points

2022-08-07T12:13:35.463+00:00
thanks - I'm still having this problem
the File.delete works on the emulator but on real Android phones (sdk 29 and 31) no exception is thrown result says it is deleted but its still there

this is the code - you can see I am requesting permission before hand (actually it was this addition which seemed to make it work on emulator but not on a live phone
'csvorig' is the name and path of file chosen through filepicker

I know that recent versions of Android have made it much more difficult to manage files but ALL Microsoft Learn say this should work on Maui.

status = await Permissions.CheckStatusAsync<Permissions.StorageWrite>();
if (status == PermissionStatus.Denied)
{
await DisplayAlert("warn", "Sorry cannot grant permission \n you will need to delete this file using filemanager \n" + csvorig, "cancel");
return;
}
try
{
File.Delete(csvorig);
}
catch (Exception ee)
{
var m = ee.Message;
await DisplayAlert("", m, "Cancel");
}

if (File.Exists(csvorig)) { await DisplayAlert("warn", "failed to delete", "cancel"); } else { await DisplayAlert(csvorig, "has been deleted", "back"); }

the android manifest looks like this
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_INTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" />
<uses-permission android:name="android.permission.MANAGE_USB" />
<uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.USE_CREDENTIALS" />
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<uses-permission android:name="android.permission.MOUNT_FORMAT_FILESYSTEMS" />
<uses-permission android:name="android.permission.MANAGE_DOCUMENTS" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
Flávio Afonso Klein 5 Reputation points

2023-05-24T20:54:22.8566667+00:00

I have the same problem, but in FileSystem.AppDataDirectory.

I can create a file, but I can't delete it and update it.

The most crazy is that it no shows errors or exceptions.

Simply not exclude the file or not update it.

All of my asks to Mr.google and documentation shows me that my routines are fine, credentials and manifests too.

I don't undertand!

Example:

1 - On one part of App the user signs one document, and the App save the image on file, and the file path on database. In the another moment, upload document data and image file to cloud. Here it needs exclude data in dabatase and the image file.

2 - On another moment, also on syncronize data with cloud ...

Some image files are downloaded to App show them during the CRUD operations. In the first time everything go nice.

But if on cloud any image has been updated ... on downloading the App can't exclude or update the local image files.

That's drives me crazy.

What I should do to resolve this problem?

Richard Barraclough 6

Same problem.

The file gets deleted on Windows but on Android the loop is infinite.

            string newPath = Path.Combine(File.Directory.FullName, NewName);
            System.IO.File.Move(File.FullName, newPath);
            System.IO.File.SetCreationTime(newPath, ImageDate);
            while (System.IO.File.Exists(File.FullName))
            {
                System.IO.File.Delete(File.FullName);
            }

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