C# Query: 'System.InvalidOperationException' | Additional information: Connection must be valid and open

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();

Hello,

I have this problem when I run the following code. I get this not so very specific error:

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

Additional information: Connection must be valid and open.

If anyone could help me out I would really appreciate it,

Thank you.

Well the exception seems pretty clear. You don't have a valid, open connection. Look at your code - where do you think you're opening the connection? Try `connect.Open()`... — Jon Skeet, Feb 23 '15 at 10:56
The connection is already opened by another methode. When I add connect.Open() it says the connection is already open. — Quartermain, Feb 23 '15 at 11:00
Then there's code you haven't shown us, which makes it hard to help you... — Jon Skeet, Feb 23 '15 at 11:00
I up voted just because, after programming for 12 hours straight, I also left out the Open statement ... then spent 10 minutes wondering what was wrong. Sometimes the obvious mistakes are the ones we don't see. Thank goodness for SO! :D — Yogi, Sep 17 '16 at 06:41

score 0 · Answer 1 · answered Feb 23 '15 at 12:21

0

The syntax for MySql Connectionstring is as follows:

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

Note that you are using 'userid' and 'password' instead of 'uid' and 'pwd'.

answered Feb 23 '15 at 12:21

score 0 · Answer 2 · edited May 23 '17 at 12:32

Assuming that your Connection String is Right .. Try This

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();

You Can Refer this Link for Reference. Exception: System.InvalidOperationException Trying to validate a login information

Hope This Helps :)

C# Query: 'System.InvalidOperationException' | Additional information: Connection must be valid and open

2 Answers2

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