C#

if (textBox9.Text != "" && textBox10.Text != "")
            {
                string connectionString;
                MySqlConnection cnn;
                connectionString = @"Data Source=localhost;Initial Catalog=testDB;User ID=root;Password=mysql";
                cnn = new MySqlConnection(connectionString);
                string id = textBox9.Text;
                string password = textBox10.Text;
                textBox9.Text = "";
                textBox10.Text = "";
                string query = "select * from login where userid=@userid and password=@password";
                using (MySqlCommand cmd = new MySqlCommand(query))
                {
                   cmd.Parameters.AddWithValue("@userid", id);
                   cmd.Parameters.AddWithValue("@password", password);
                    cmd.Connection = cnn;
                    cnn.Open();
                    cmd.ExecuteNonQuery();
                    DialogResult dr = MessageBox.Show("Are you sure to Login now?", "Confirmation Message", MessageBoxButtons.YesNo);
                    if (dr == DialogResult.Yes)
                    {
                        MessageBox.Show("Login Successfully");
                        cnn.Close();
                        this.Hide();
                        Form2 f2 = new Form2();
                        f2.ShowDialog();
                    }
                    else if (dr == DialogResult.No)
                    {
                        MessageBox.Show("Please Enter Correct Login details");
                    }
                }
            }
            else
            {
                MessageBox.Show("Please Enter With Correct Login Details");
            }

Richard Deeming wrote:

You can't change attributes at run-time;