Database query C# not working

Question

I've read many ODBC tutorials for C# on the net, and this code is the only one that didn't give me error. But the problem is, it doesn't do anything -.- How to fix ??

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
using System.Data.Odbc;
using System.Data.Sql;
namespace WindowsFormsApplication1
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
        string connectionString = "Server=localhost;User       ID=root;Password=****;Database=testing;Port=3306;Pooling=false";
        MySql.Data.MySqlClient.MySqlConnection connection = new MySql.Data.MySqlClient.MySqlConnection(connectionString);

        connection.Open();

        string insertQuery = "ALTER TABLE `user` ADD lol INT (15)";
        MySql.Data.MySqlClient.MySqlCommand myCommand = new MySql.Data.MySqlClient.MySqlCommand(insertQuery);
        connection.Close();
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new Form1());
    }
}
}

I'd suggest looking at the `using Statement` and `try/catch/finally` when working with something such as DB connections. — myermian, Nov 20 '10 at 13:32
@Frederic - Thats not very helpful. What he meant to say was you can either use VARCHAR(15) or INT. Not INT(15). I don't think thats your problem though because that would throw an exception. The problem must be before that. Have you tried stepping through your code in debug mode. — Ash Burlaczenko, Nov 20 '10 at 13:33
@Ash, you're probably right. Too many strange questions today I guess. — Frédéric Hamidi, Nov 20 '10 at 13:35
Asked the same question here: http://stackoverflow.com/questions/4233185/connection-must-be-valid-and-open-error — Fernando, Nov 20 '10 at 14:52

score 2 · Accepted Answer · answered Nov 20 '10 at 13:30

2

You need to execute the command:

myCommand.ExecuteNonQuery();

answered Nov 20 '10 at 13:30

Klaus Byskov Pedersen

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Why would you want it to run more than once? – Ash Burlaczenko Nov 20 '10 at 13:35
"Connection must be valid and open" it says now – Marcus Nov 20 '10 at 13:36
You need to pass along the connection to the Command object. Either by constructor, or property. – Claus Jørgensen Nov 20 '10 at 13:52

score 2 · Answer 2 · answered Nov 20 '10 at 13:49

Allow me to tidy; important points:

using to ensure proper disposal
setting the command's Connection
executing the command with ExecuteNonQuery()

Code:

Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
string connectionString = "Server=localhost;User ID=root;Password=****;Database=testing;Port=3306;Pooling=false";
string insertQuery = "ALTER TABLE `user` ADD lol INT (15)";
using(MySql.Data.MySqlClient.MySqlConnection connection =
    new MySql.Data.MySqlClient.MySqlConnection(connectionString))
using(MySql.Data.MySqlClient.MySqlCommand myCommand =
    new MySql.Data.MySqlClient.MySqlCommand(insertQuery))
{
    myCommand.Connection = connection;
    connection.Open();
    myCommand.ExecuteNonQuery();
    connection.Close();
}
using(Form1 form1 = new Form1()) {
    Application.Run(form1);
}

Database query C# not working

2 Answers2

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