public static void tt()
        {
            int ID = 0;

            while(true)
            {
                string datasource = System.Environment.CurrentDirectory + "\\test.db";
                if (!File.Exists(datasource))
                {
                    System.Data.SQLite.SQLiteConnection.CreateFile(datasource);
                }

                System.Data.SQLite.SQLiteConnection conn = new System.Data.SQLite.SQLiteConnection();
                System.Data.SQLite.SQLiteCommand cmd = new System.Data.SQLite.SQLiteCommand();
                StringBuilder sb = new StringBuilder();

                try
                {
                    System.Data.SQLite.SQLiteConnectionStringBuilder connstr = new System.Data.SQLite.SQLiteConnectionStringBuilder();
                    connstr.DataSource = datasource;
                    connstr.Password = "admin";
                    conn.ConnectionString = connstr.ToString();
                    conn.Open();

                    string sql = string.Empty;

                    cmd.Connection = conn;

                    sql = "select count(*) from sqlite_master where type=‘table‘ and name=‘test‘;";
                    cmd.CommandText = sql;
                    using (System.Data.SQLite.SQLiteDataReader reader1 = cmd.ExecuteReader())
                    {
                        if (reader1.Read() && 0 == reader1.GetInt16(0))
                        {
                            reader1.Dispose();

                            //创建表
                            sql = "CREATE TABLE test(id int,username varchar(20),password varchar(20))";
                            cmd.CommandText = sql;
                            cmd.Connection = conn;
                            cmd.ExecuteNonQuery();
                        }
                    }

                    //插入数据
                    sql = string.Format("INSERT INTO test VALUES({0},‘a‘,‘b‘)",++ID);
                    cmd.CommandText = sql;
                    cmd.ExecuteNonQuery();

                    //取出数据
                    sql = "SELECT * FROM test";
                    cmd.CommandText = sql;

                    using (System.Data.SQLite.SQLiteDataReader reader = cmd.ExecuteReader())
                    {
                        int count = 0;
                        while (reader.Read())
                        {
                            sb.Append("id:").Append(reader.GetInt64(0)).Append(",");
                            sb.Append("username:").Append(reader.GetString(1)).Append(",")
                            .Append("password:").Append(reader.GetString(2)).Append("\n");
                        }
                    }
                }
                finally
                {
                    cmd.Dispose();
                    conn.Dispose();
                }

                Console.WriteLine(sb.ToString());

                Thread.Sleep(0);
            }