CODEWITHSUNDEEP
c#sqlitexamarin
David
David

Reputation: 2324

Zip file extraction when restoring a database

I've created a backup and restore procedure for my application. When the backup is run, it will create a .zip file of the SQLite database in the same directory as the database.

When restoring the database, it will rename the database, changing it from EPOSDatabase.db3 to tempEPOS.db3

Then, it takes the selected file and extracts it to the same location, under the name EPOSDatabase.db3, before deleting the renamed temporary database.

string dbPath = Environment.GetFolderPath(Environment.SpecialFolder.Personal);

if (File.Exists(dbPath + "/tempEPOS.db3"))
  {
    File.Delete(dbPath + "/tempEPOS.db3");
  };

  File.Move(dbPath + "/EPOSDatabase.db3", dbPath + "/tempEPOS.db3");

  ZipFile.ExtractToDirectory(dbPath + "/" + fileToRestore, dbPath + "/EPOSDatabase.db3");

  File.Delete(dbPath + "/tempEPOS.db3");

My issue is that when I then have code that opens the connection, for example when I open the system settings page after the restore has been carried out, I get an error:

"Could not open database file: /data/user/0/com.companyname.ACPlus_MobileEPOS/files/EPOSDatabase.db3 (CannotOpen)"

As a further debug test, I added this code to the startup of the application:

string path = Environment.GetFolderPath(Environment.SpecialFolder.Personal);

foreach (var file in Directory.GetFiles(path))
{
   string strFile = Convert.ToString(file);
}

public readonly string dbPath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Personal), "EPOSDatabase.db3");

var db = new SQLiteConnection(dbPath);
db.CreateTable<Category>();
db.CreateTable<SystemSettings>();

db.Close();

In the foreach loop, it only found the original .zip file that I was trying to restore from.

Then when it reaches the line var db = new SQLiteConnection(dbPath);

it fails to create the database with the message

"Could not open database file: /data/user/0/com.companyname.ACPlus_MobileEPOS/files/EPOSDatabase.db3"

It seems like the file doesn't exist, so hasn't extracted properly, but if that was the case then why does it not just create a new database, rather than try to open it?

Upvotes: 1

Views: 661

Answers (1)

Nkosi
Nkosi

Reputation: 247531

The extraction logic needs to be rechecked.

Specifically ExtractToDirectory.

Extracts all the files in the specified zip archive to a directory on the file system.

public static void ExtractToDirectory (string sourceArchiveFileName, string destinationDirectoryName);

In the original code

ZipFile.ExtractToDirectory(dbPath + "/" + fileToRestore, dbPath + "/EPOSDatabase.db3");

The contents of the zip file are extracting to a directory called {path}/EPOSDatabase.db3/.

If the goal was just to extract from the archive to the directory then only the directory location is required.

ZipFile.ExtractToDirectory(dbPath + "/" + fileToRestore, dbPath);

Additionally, a check should be done to make sure the desired file actually exists after the restore before deleting the old file.

//... extraction code omitted for brevity

if (!File.Exists(dbPath + "/EPOSDatabase.db3")) {
    //...either throw error or alert that database is not present

    //...could consider return old file back to original sate (optional)
} else {
    File.Delete(dbPath + "/tempEPOS.db3");
}

Upvotes: 2

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