C＃查詢：'System.InvalidOperationException'|其他信息：連接必須是有效和打開

Question

connectionString = @"server=localhost;database=" + lbDatabase.SelectedItem.ToString() + ";userid=root;password=;"; 

     string query = "SELECT order_id FROM orders WHERE id = 1"; 

     MySqlConnection connect = new MySqlConnection(connectionString); 

     MySqlCommand cmd = new MySqlCommand(query, connect); 

     reader = cmd.ExecuteReader(); 

你好，

當我運行下面的代碼我有這個問題。我得到這個不是那麼非常具體的錯誤：

An unhandled exception of type 'System.InvalidOperationException' occurred in MySql.Data.dll

Additional information: Connection must be valid and open.

如果有人可以幫助我，我真的很感激它，

謝謝。

Answer 1

對MySQL的ConnectionString中語法如下：

Server=myServerAddress;Database=myDataBase;Uid=myUsername;Pwd=myPassword; 

請注意，您在使用「用戶ID」和而不是「UID」和「PWD」密碼'。

Answer 2

假設你的連接字符串的權利..嘗試這個

connectionString = @"server=localhost;database=" + lbDatabase.SelectedItem.ToString() + ";userid=root;password=;"; 

    string query = "SELECT order_id FROM orders WHERE id = 1"; 

    MySqlConnection connect = new MySqlConnection(connectionString); 


    MySqlCommand cmd = new MySqlCommand(query, connect); 

    connect.Open(); 

    reader = cmd.ExecuteReader(); 

/*Do Whatever You Want To Do Here */ 

connect.Close(); 

你可以參考這個鏈接引用。 Exception: System.InvalidOperationException Trying to validate a login information

希望這有助於:)