Why Am I Getting "Connection Must Be Valid And Open Error"? This Was Ok Before. Hmm

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C#

private void button1_Click(object sender, EventArgs e)
        {
            using (MySqlConnection con = new MySqlConnection("Server=localhost;UID=root;Database=db_cignal"))
            {
                con.Open();
                MySqlCommand command = new MySqlCommand();
                command.Connection = con;
                command.CommandText = "SELECT * FROM Admin";
                command.Prepare();
                MySqlDataReader read = command.ExecuteReader();

                while (read.Read())
                {

                    if (txtName.Text.Equals(read["Username"].ToString()) && txtPass.Text.Equals(read["Password"].ToString()))
                    {
                        MessageBox.Show("***Login Successfully***");
                        this.Hide();
                        Administrator form2 = new Administrator();
                        form2.Closed += (s, args) => this.Close();
                        form2.Show();
                    }
                    else
                    {
                        MessageBox.Show("Please input the correct username or password..");
                        txtName.Text = "";

                        txtPass.Text = "";
                    }

                }
                read.Close();
                con.Close();
                }
            }

Posted 22-Mar-15 23:07pm

_bluRe_

Updated 22-Mar-15 23:10pm

RajeeshMenoth

v2

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OriginalGriff · Accepted Answer · 2015-03-22T23:14:00

The most likely reason is the connection string: fixed strings in your code often give problems. You don't say what you were doing before when it worked, or what has changed since then, but this kind of thing is often because you specify "localhost" as the server, and then move to a different computer - where the DB server is not installed.

I'd suggest that you move your connection string to a config file of some description so you can alter it without recompilation, and look at the environment in which you are trying to run the application. Specifically, look at the DB servers installed, and see if you need a different connection string - a different server name, an actual login, and so forth.

We can't do that for you - we can't access your systems! :laugh:

BTW: Never store passwords in clear text - it is a major security risk. There is some information on how to do it here: Password Storage: How to do it.[^]