Database not persisted between builds with xamarin 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