input string was not in a correct format

لدي هذا الكود وعند تشفيل البرنامج تظهر رسالة الخطأ "   input string was not in a correct format" , علما بأني الحقل هو خقل رئيسي في قاعد البيانات وقرأت انه يمكن اسخدام  TryParse؟ 

Manage Employee Form 

private void button_update_Click(object sender, EventArgs e)
        {
            // update student record
             int id = Convert.ToInt32(textBox_id.Text);
            string name = textBox_EmpName.Text;
            string title = textBoxJob_Title.Text;
            string position = textBoxPosition.Text;
            DateTime hdate = dateTimePicker_hd.Value;
            string country = textBoxCountry.Text;
            DateTime bdate = dateTimePicker_bd.Value;
            string phone = textBox_phone.Text;
            string address = textBox_address.Text;
            string gender = radioButton_male.Checked ? "Male" : "Female";


            //we need to check student age between 10 and 100

            int born_year = dateTimePicker_bd.Value.Year;
            int this_year = DateTime.Now.Year;
            if ((this_year - born_year) < 10 || (this_year - born_year) > 100)
            {
                MessageBox.Show("The employee age must be between 10 and 100", "Invalid Birthdate", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            else if (verify())
            {
                try
                {
                    // to get photo from picture box
                    MemoryStream ms = new MemoryStream();
                    pictureBox_employee.Image.Save(ms, pictureBox_employee.Image.RawFormat);
                    byte[] img = ms.ToArray();
                    if (employee.updateEmployee(id,name, title, position, hdate, country, bdate, gender, phone, address, img))

                    {
                        showTable();
                        MessageBox.Show("Employee data update", "Update Employee", MessageBoxButtons.OK, MessageBoxIcon.Information);
                        button_clear.PerformClick();
                    }
                }
                catch (Exception ex)

                {
                    MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
            }
            else
            {
                MessageBox.Show("Empty Field", "Update Employee", MessageBoxButtons.OK, MessageBoxIcon.Warning);
            }


        }

Employee class 

 public bool updateEmployee(int id, string name, string title, string position, DateTime hdate, string country, DateTime bdate, string gender, string phone, string address, byte[] img)
        {
            MySqlCommand command = new MySqlCommand("UPDATE `employee` SET `EmpName`=@n,`Job_Title`=@jt,'Position'=@p,'Hiring_Date'=@hd,'Country'=@c,`Birthdate`=@bd,`Gender`=@gd,`Phone`=@ph,`Address`=@adr,`Photo`=@img WHERE  `EmpId`= @id", connect.getconnection);

            //@id,@fn, @ln, @bd, @gd, @ph, @adr, @img
            command.Parameters.Add("@id", MySqlDbType.Int32).Value = id;
            command.Parameters.Add("@n", MySqlDbType.VarChar).Value = name;
            command.Parameters.Add("@jt", MySqlDbType.VarChar).Value = title;
            command.Parameters.Add("@p", MySqlDbType.VarChar).Value = position;
            command.Parameters.Add("@hd", MySqlDbType.VarChar).Value = hdate;
            command.Parameters.Add("@c", MySqlDbType.VarChar).Value = country;
            command.Parameters.Add("@bd", MySqlDbType.VarChar).Value = bdate;
            command.Parameters.Add("@gd", MySqlDbType.VarChar).Value = gender;
            command.Parameters.Add("@ph", MySqlDbType.VarChar).Value = phone;
            command.Parameters.Add("@adr", MySqlDbType.VarChar).Value = address;
            command.Parameters.Add("@img", MySqlDbType.Blob).Value = img;

            connect.openConnect();
            if (command.ExecuteNonQuery() == 1)
            {
                connect.closeConnect();
                return true;
            }
            else
            {
                connect.closeConnect();
                return false;
            }

        }
        //Create a function to delete data
        //we need only id 
        public bool deleteEmployee(int id)
        {
            MySqlCommand command = new MySqlCommand("DELETE FROM `employee` WHERE `EmpId`=@id", connect.getconnection);

            //@id
            command.Parameters.Add("@id", MySqlDbType.Int32).Value = id;
            
            connect.openConnect();
            if (command.ExecuteNonQuery() == 1)
            {
                connect.closeConnect();
                return true;
            }
            else
            {
                connect.closeConnect();
                return false;
            }

        }