SQLITE Delete item does't delete for real - sqlite

Question

I got a xamarin forms app, and the problem is when I delete an item from a sqlite table, it looks like all works, the item is deleted from the collection, the grids got updated, etc, but when I restart the app, the item is still there. its like the delete only works in memory but it never got saved in the database.
my code is below
I create an instance called DB in my App constructor
public partial class App
{
static Database database;
public static Database DB
{
get
{
if (database == null)
{
string nombreBD = "MyDataBaseFile.db3";
string _databasePath = Path.Combine(Xamarin.Essentials.FileSystem.AppDataDirectory, nombreBD);
database = new Database(_databasePath);
}
return database;
}
}
................
}
I'm using sqlite with tables created from classes, like this
db = new SQLiteAsyncConnection(dbPath);
db.CreateTableAsync<MyType>().Wait();
where MyType is a class like this
public class MyType
{
[PrimaryKey]
public int Idtable { get; set; }
......
}
I try to delete a row of the table like this:
var x = await App.DB.GetItemAsync<MyType>(obj.Idtable );
int regsDeleted = await App.DB.DeleteItemAsync<MyType>(x);
the GetItemsAsync is basically: await db.FindAsync<T>(id);
public async Task<T> GetItemAsync<T>(int id) where T : new()
{
try
{
return await db.FindAsync<T>(id);
}
catch (System.Exception ex)
{
throw new System.Exception($"Error sqlLite {MethodBase.GetCurrentMethod().Name}: {ex.Message}");
}
}
and the delete method is this:
public async Task<int> DeleteItemAsync<T>(T item) where T : new()
{
try
{
int regsDeleted=await db.DeleteAsync(item);
db.GetConnection().Commit();
return regsDeleted;
}
catch (System.Exception ex)
{
throw new System.Exception($"Error sqlLite {MethodBase.GetCurrentMethod().Name}: {ex.Message}");
}
}
like I said I got no errors and all looks like worked, but when restart the app, the item still there!!
any Idea? something to add in the connection maybe? transactions?... any help will be great
thanks
UPDATE After a lot of test I realize the problem is not the delete. The problem is that every time I run the app from VS to my android device through USB cable, I don't know how or why the database get restored from some backup, that I don´t know when or where was done. Looks like Android have a backup and the "data" of my app and when a new version comes he just restore the data. I read somne that said the Xamarin.Essentials.FileSystem.AppDataDirectory should not be used to save databases, so the question is. where is th right place to save the SQLLite database.Any Idea? My app don't deployed an empty database, my app create the database in the first execution. Does anyone knows how to avoid that restauration of the folder? every time I run the app from VisualStudio ?

Answer 1

The DeleteAsync works without Commit. I make come changes for your code. It works on my side.
I add the PrimaryKey and AutoIncrement attributes to ensure that each Note instance in the SQLite.NET database will have a unique id provided by SQLite.NET.
public class MyType
{
[PrimaryKey, AutoIncrement]
public int Idtable { get; set; }
public string Text { get; set; }
}
The code for the connect to the database, save the record, delete the row and get the all the items.
readonly string _databasePath = Path.Combine(Xamarin.Essentials.FileSystem.AppDataDirectory, "MyDataBaseFile.db3");
SQLiteAsyncConnection database;
public MyType myType { get; set; }
int i = 0;
public Page2()
{
InitializeComponent();
}
private void Connect_Clicked(object sender, EventArgs e)
{
database = new SQLiteAsyncConnection(_databasePath);
database.CreateTableAsync<MyType>().Wait();
}
async void Save_Clicked(object sender, EventArgs e)
{
myType = new MyType() { Text = "Hello" + i };
if (myType.Idtable != 0)
{
// Update an existing note.
await database.UpdateAsync(myType);
i++;
}
else
{
// Save a new note.
await database.InsertAsync(myType);
i++;
}
}
async void Delete_Clicked(object sender, EventArgs e)
{
var x = await database.FindAsync<MyType>(myType.Idtable);
int regsDeleted = await database.DeleteAsync(x);
}
async void Get_Clicked(object sender, EventArgs e)
{
var s = await database.Table<MyType>().ToListAsync();
try
{
var s2 = await database.FindAsync<MyType>(myType.Idtable);
}
catch
{
return;
}
}
}
Please note if i restart the app, there is no myType.Idtable. So i use the try catch to make my project run.
Add four items for the database and detele the last one.
After restart the app, the items:

Answer 2

I had a similar error. Very annoying and couldn't figure it out. After reading this question I have just deleted the db3 file on the android device rerun my app and now it works. I suspect that during development and changing the structure of the class for the table something gets screwed up. Deleting the database db3 (or whatever, sqlite doesn't care) re-created the the tables completely.
So how do you get to the file? (For a Pixel 5 emulator)
I used Android Studio and the DeviceFileExplorer (View>ToolWindows)
But where is it. Well In my app I use
private readonly static string filename = "xxx.db3";
...
database = new Database.Database(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), filename));
and I (eventually) found this located in data>data>(my Application Id)>files
where my ApplicationID is something like uk.co.mydomainname.myappname
I just then deleted the file with a right click delete
(Note: I found sometimes you have to right click the files folder and synchronise to refresh the tree and see the db file)
Hope this helps.
PS I wish for me (.net maui) the documentation explained more clearly the paths and where things get located/placed!!