sqllite连接字符串问题

C# code

   string m_strConnectionString = "Data Source=" + AppDomain.CurrentDomain.SetupInformation.ApplicationBase + @"stations.dat";            SQLiteConnection conn = new SQLiteConnection(m_strConnectionString);            conn.Open();            string sql = "select * from citys";            SQLiteCommand cmd = new SQLiteCommand(sql,conn);            cmd.ExecuteReader();            SQLiteDataReader sda = cmd.ExecuteReader();//这里报错DataReader already active on this command            while(sda.Read())             {                sda["name"].ToString();            }

[解决办法]
cmd.ExecuteReader();//这里已经执行了，注释
SQLiteDataReader sda = cmd.ExecuteReader();//这里报错DataReader already active on this command