Working with sqlite and moving functions to class

I want to move this to a class that will open an sqlite connection that can be re-used, rather than disposing of it every time I write to the database. Furthermore I am more than happy for any best practices from sqlite users! I am aware of a similar thread and am trying to absorb it:

SQLite helper class

void createDB()
{
    // Dont forget to del if refreshing
    if (!File.Exists(connstring))
    {
        SQLiteConnection.CreateFile(connstring);
        SQLiteConnection sqliteCon = new SQLiteConnection(@"Data Source=" + connstring);
        sqliteCon.Open();

        // Define db structure
        string createfilesTableSQL = "CREATE TABLE files ( id INTEGER PRIMARY KEY, filename TEXT, creationtime TEXT, lastwrite TEXT, lastaccess TEXT, checksum TEXT);";
        string createfoldersTableSQL = "CREATE TABLE folders ( id INTEGER PRIMARY KEY, dirname TEXT, creationtime TEXT, lastwrite TEXT, lastaccess TEXT, checksum TEXT);";

        using (SQLiteTransaction sqlTransaction = sqliteCon.BeginTransaction())
        {
            // Create the tables
            SQLiteCommand createCommand = new SQLiteCommand(createfilesTableSQL, sqliteCon);
            createCommand.ExecuteNonQuery();
            createCommand.Dispose();

            SQLiteCommand createCommand2 = new SQLiteCommand(createfoldersTableSQL, sqliteCon);
            createCommand2.ExecuteNonQuery();
            createCommand2.Dispose();

            // Commit the changes into the database
            sqlTransaction.Commit();
        } // end using

        // Close the database connection
        sqliteCon.Close();
        sqliteCon.Dispose();
    }
}
public int fileExists(string filename, string lastwrite, string hash)
{
    /* Here is a quick Map
     0 "The file does not exist in the database
     1 "The Hash Matches, leave it alone
     2 "the file is newer than that of the databse
     3 "the file is older than that of the databse"
     4 "the file is the same as that of the database"
     */

    // Connect to database
    SQLiteConnection sqliteCon = new SQLiteConnection(@"Data Source=" + connstring);
    sqliteCon.Open();

    //Query
    //string selectSQL = "SELECT EXISTS(SELECT 1 FROM files WHERE filename=" + filename + " LIMIT 1) as result;";
    string selectSQL = "SELECT * FROM files WHERE filename=" + filename + ";";
    SQLiteCommand selectCommand = new SQLiteCommand(selectSQL, sqliteCon);
    SQLiteDataReader dataReader = selectCommand.ExecuteReader();

    //does file exist
    bool exists = dataReader.Read();

    if (!exists)
    {
        dataReader.Dispose();
        sqliteCon.Dispose();
        return 0; //it doesnt exist in the database
    }

    string dbhash = dataReader["checksum"].ToString();
    string dblastwrite = dataReader["lastwrite"].ToString();
    string lastwritex = lastwrite.Replace("'", "");
    string hashx = hash.Replace("'", "");
    DateTime dblastwriteDT = Convert.ToDateTime(dblastwrite);
    DateTime lastwriteDT = Convert.ToDateTime(lastwritex);

    dataReader.Dispose();
    sqliteCon.Dispose();


    if (dbhash == hashx)
    {
        return 1; //hash matches the database version
    }

    if (lastwriteDT > dblastwriteDT)
    {
        return 2; //the file is newer than that of the databse
    }

    if (lastwriteDT < dblastwriteDT)
    {
        return 3; //the file is older than that of the databse
    }
    else
    {
        return 4; //the file is the same as that of the database
    }
}
void cleanDB()
{
    SQLiteConnection sqliteCon = new SQLiteConnection(@"Data Source=" + connstring);
    sqliteCon.Open();

    // Define db structure
    string createfilesTableSQL = "delete from files;";
    string createfoldersTableSQL = "delete from folders;";

    using (SQLiteTransaction sqlTransaction = sqliteCon.BeginTransaction())
    {
        // Create the tables
        SQLiteCommand createCommand = new SQLiteCommand(createfilesTableSQL, sqliteCon);
        createCommand.ExecuteNonQuery();
        createCommand.Dispose();

        SQLiteCommand createCommand2 = new SQLiteCommand(createfoldersTableSQL, sqliteCon);
        createCommand2.ExecuteNonQuery();
        createCommand2.Dispose();

        // Commit the changes into the database
        sqlTransaction.Commit();
    } // end using

    // Close the database connection
    sqliteCon.Dispose();
}
private void addFile(string filename, string creationtime, string lastwrite, string lastaccess, string checksum)
{
    // Open connection to database
    SQLiteConnection sqliteCon = new SQLiteConnection(@"Data Source=" + connstring);
    sqliteCon.Open();
    using (SQLiteTransaction SQLiteTrans = sqliteCon.BeginTransaction())
    {
        using (SQLiteCommand cmd = sqliteCon.CreateCommand())
        {
            // Insert a new file record
            cmd.CommandText = "INSERT INTO files(filename, creationtime, lastwrite, lastaccess, checksum)" + " VALUES (?,?,?,?,?)";

            SQLiteParameter Field1 = cmd.CreateParameter();
            SQLiteParameter Field2 = cmd.CreateParameter();
            SQLiteParameter Field3 = cmd.CreateParameter();
            SQLiteParameter Field4 = cmd.CreateParameter();
            SQLiteParameter Field5 = cmd.CreateParameter();

            cmd.Parameters.Add(Field1);
            cmd.Parameters.Add(Field2);
            cmd.Parameters.Add(Field3);
            cmd.Parameters.Add(Field4);
            cmd.Parameters.Add(Field5);
            Field1.Value = filename;
            Field2.Value = creationtime;
            Field3.Value = lastwrite;
            Field4.Value = lastaccess;
            Field5.Value = checksum;

            cmd.ExecuteNonQuery();
        }

        SQLiteTrans.Commit();
    }
    sqliteCon.Dispose();
}
private void addFolder(string dirname, string creationtime, string lastwrite, string lastaccess, string checksum)
{

    // Open connection to database
    SQLiteConnection sqliteCon = new SQLiteConnection(@"Data Source=" + connstring);
    sqliteCon.Open();
    using (SQLiteTransaction SQLiteTrans = sqliteCon.BeginTransaction())
    {
        using (SQLiteCommand cmd = sqliteCon.CreateCommand())
        {
            // Insert a new file record
            cmd.CommandText = "INSERT INTO folders(dirname, creationtime, lastwrite, lastaccess, checksum)" + " VALUES (?,?,?,?,?)";

            SQLiteParameter Field1 = cmd.CreateParameter();
            SQLiteParameter Field2 = cmd.CreateParameter();
            SQLiteParameter Field3 = cmd.CreateParameter();
            SQLiteParameter Field4 = cmd.CreateParameter();
            SQLiteParameter Field5 = cmd.CreateParameter();

            cmd.Parameters.Add(Field1);
            cmd.Parameters.Add(Field2);
            cmd.Parameters.Add(Field3);
            cmd.Parameters.Add(Field4);
            cmd.Parameters.Add(Field5);
            Field1.Value = dirname;
            Field2.Value = creationtime;
            Field3.Value = lastwrite;
            Field4.Value = lastaccess;
            Field5.Value = checksum;

            cmd.ExecuteNonQuery();
        }

        SQLiteTrans.Commit();
    }
    sqliteCon.Dispose();
}