尝试查询数据库时收到错误“未选择数据库”

我是一所职业高中的学生，我对编程还是很陌生，我被分配使用c＃创建一个应用程序，并且在连接3个表以显示在datagridview上时遇到问题。在mySql上它可以正常工作，但是当我在我的c＃代码行中应用它却没有起作用时，它显示“未选择数据库”，有人可以帮我解决这个问题，这是我的完整代码

string constring = "datasource=localhost;port=3306;username=root;password=root";
        MySqlConnection conDataBase = new MySqlConnection(constring);
        MySqlCommand cmdDataBase = new MySqlCommand("select book_detail.id_bookdetail, location.location_id, location.location_name, book.book_id, book.title from location inner join book_detail on location.location_id = book_detail.location_id inner join book on book_detail.book_id = book.book_id; ", conDataBase);
        try
        {
            MySqlDataAdapter sda = new MySqlDataAdapter();
            sda.SelectCommand = cmdDataBase;
            DataTable dbdataset = new DataTable();
            sda.Fill(dbdataset);
            BindingSource bSource = new BindingSource();

            bSource.DataSource = dbdataset;
            transfer_view.DataSource = bSource;
            sda.Update(dbdataset);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }