SQLite Except: The database file is locked

Hi

I'm developing a game with Sqlite and WCF. But they only work fine together at the first run, if I try play scene again, console show "SQLite Except: The database file is locked", Help!

Codes below

 LobbyServiceClient _client = new LobbyServiceClient(_binding,_endpoint);
 
 _client.DoSomething();
 
 try {
             if (_client.State!=CommunicationState.Faulted) {
                 //_client.Close();
                 _client.Abort();

}}catch (System.Exception ex) { _client.Abort(); }

string _sql ="Some Select Function";

SqliteHelper _db = new SqliteHelper("client.db");

         _db.Conn.Open();
         DataTable _dt=  _db.Q(_sql);
         _db.Conn.Close();