C# MySQL. Ubable to execute query

Question

 private void button4_Click(object sender, EventArgs e)
        {
            MySqlConnection connection = new MySqlConnection("datasource=localhost;port=3306;Initial Catalog='liblib';Data Source=localhost;username=root;password=admin");

            String query = "UPDATE loans SET dataRet=@data1 WHERE loans.idloans = @idloan";
            MySqlCommand cmd = new MySqlCommand(query, connection);

            int id = Int32.Parse(textBox9.Text);


                cmd.Parameters.Add("@data1", MySqlDbType.Date).Value = dateTimePicker1.Value;
                cmd.Parameters.Add("@idloan", MySqlDbType.Int32).Value = id;



                connection.Open();

                if (cmd.ExecuteNonQuery() == 1)
                {

                    MessageBox.Show("Succesful!");


                    connection.Close();

                    FIllCard();


                }


            else
            {

                MessageBox.Show("Error");
                connection.Close();
            }

When I execute this UPDATE query in phpmyadmin it works and updates the entry:

UPDATE loans SET dataRet='2017-5-6' WHERE loans.idloans = 23.

But the problem is when I try it in my Form whith parameters. It always returns me "Error" message(ExecuteNonQuery is different from 1), and when I check the database there is no update. The type of the variables in my database are: idloans - int; dataRet = date;

Answer 1

Check out this post: update a mySQL table using C#, It does not have an answer marked as solution, but the OP of that question has authentication problems after using the code of the first answer, perhaps it works for you