Database not persisted between builds with xamarin ios - ios

Question

I'm creating a simple sqlite driven app for ios using xamarin studio on a mac.
The sqlite file is created in the "personal" folder and is persisted between builds but when i run the app the tables i created in the previous debug session is gone?
In my code, after checking that the file exists, i connect using a sqliteconnection and create a table and insert a row with the executenonquery method from the command object. While in the same context i can query the table using a second command object but if i stop the debugger and restart the table i gone?
Should i have the file in a different folder, is it a setting in xamarin or ios to keep the tables? Am i unintentionally using temp tables in sqlite or what could be the problem?
Note: so far i'm only using starter version of xamarin and debugging on iphone simulator.
public class BaseHandler
{
private static bool DbIsUpToDate { get; set; }
const int DB_VERSION = 1; //Created DB
const string DB_NAME = "mydb.db3";
protected const string CNN_STRING = "Data Source=" + DB_NAME + ";Version=3";
public BaseHandler ()
{
//No need to validate database more than once on each restart.
if (DbIsUpToDate)
return;
CheckAndCreateDatabase(DB_NAME);
int userVersion = GetUserVersion();
UpdateDBToVersion(userVersion);
DbIsUpToDate = true;
}
int GetUserVersion()
{
int version = 0;
using (var cnn = new SqliteConnection(CNN_STRING))
{
cnn.Open();
using (var cmd = cnn.CreateCommand())
{
cmd.CommandText = "CREATE TABLE UVERSION (VERSION INTEGER);" +
"INSERT INTO UVERSION (VERSION) VALUES(1);";
cmd.ExecuteNonQuery();
}
using (var cmd = cnn.CreateCommand())
{
cmd.CommandText = "SELECT VERSION FROM UVERSION;";
var pragma = cmd.ExecuteScalar();
version = Convert.ToInt32((long)pragma);
}
}
return version;
}
void UpdateDBToVersion(int userVersion)
{
//Prepare the sql statements depending on the users current verion
var sqls = new List<string> ();
if (userVersion < 1)
{
sqls.Add("CREATE TABLE IF NOT EXISTS MYTABLE ("
+ " ID INTEGER PRIMARY KEY, "
+ " NAME TEXT, "
+ " DESC TEXT "
+ ");");
}
//Execute the update statements
using (var cnn = new SqliteConnection(CNN_STRING))
{
cnn.Open();
using (var trans = cnn.BeginTransaction(System.Data.IsolationLevel.ReadCommitted))
{
foreach(string sql in sqls)
{
using (var cmd = cnn.CreateCommand())
{
cmd.CommandText = sql;
cmd.ExecuteNonQuery();
}
}
trans.Commit();
//SetUserVersion(DB_VERSION);
}
}
}
protected string GetDBPath (string dbName)
{
// get a reference to the documents folder
var documents = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
// create the db path
string db = Path.Combine (documents, dbName);
return db;
}
protected void CheckAndCreateDatabase (string dbName)
{
var dbPath = GetDBPath(dbName);
// determine whether or not the database exists
bool dbExists = File.Exists(dbPath);
if (!dbExists)
SqliteConnection.CreateFile(dbPath);
}
}
Again, my problem is that every time I run the debugger it runs GetUserVersion but the table UVERSION is not persisted between sessions. The "File.Exists(dbPath)" returns true so CreateFile is not run. Why is the db empty?

Answer 1

This is a code snippet I've used to save my databases in the iOS simulator and the data seems to persist between app compiles just fine:
string documentsPath = Environment.GetFolderPath (Environment.SpecialFolder.Personal);
string libraryPath = Path.Combine (documentsPath, "../Library/");
var path = Path.Combine (libraryPath, "MyDatabase.db3");
You may also want to check out the SQLite class for Xamarin off of Github:
https://github.com/praeclarum/sqlite-net/tree/master/src
Here's a tutorial on how to use said class:
http://docs.xamarin.com/recipes/ios/data/sqlite/create_a_database_with_sqlitenet

Answer 2

Turns out that I was creating the connection object using the CNN_STRING which just had the db-name instead of the full path to the db. Apperantly the connection object creates the database if the file doesn't exist so the File.Exists(...) might not be needed. I'm not really sure if it should be a temporary db if the complete path is not supplied but it seems to be the case. Changing the creation of the connection object to "datasource=" solved the problem.