insert value textbox into mysql database

Programmer Question

I have problems inserting a textboxvalue into a mysql database - there's no errormessage and no inserting. What am I doing wrong

 private void RegisterCustomer()
    {
        string firstname = txtfirstname.ToString();

        OdbcConnection conn;
        conn = new OdbcConnection(ConfigurationManager.ConnectionStrings["jConnString"].ConnectionString);
        conn.Open();

        string sql = "insert into klant (firstname) values (@firstname)";
        OdbcCommand cmd = new OdbcCommand(sql, conn);
        cmd.Parameters.Add("@firstname", OdbcType.VarChar).Value = firstname;
        try
        {
            cmd.ExecuteNonQuery();
        }
        catch (Exception ex)
        {
            Check.Text += ex.ToString() + sql;
        }
        finally
        {
            conn.Close();
            conn.Dispose();
            Check.Text += "OK";
        }
    }

Find the answer here