private void showButton_Click(object sender, EventArgs e)
        {
            employeeGridView.Rows.Clear();
            totalSalaryextBox.Text = string.Empty;
            decimal         totalSalary = 0;
            int             srl         = 0;
            List <Employee> employees   = aEmployeeManager.GetAll(Convert.ToInt32(deptComboBox.SelectedValue));

            foreach (Employee employee in employees)
            {
                employeeGridView.Rows.Add();

                employeeGridView.Rows[srl].Cells[0].Value = employee.Name;
                employeeGridView.Rows[srl].Cells[1].Value = employee.Email;
                employeeGridView.Rows[srl].Cells[2].Value = employee.Contact;
                employeeGridView.Rows[srl].Cells[3].Value = employee.Grade.GradeLevel;
                employeeGridView.Rows[srl].Cells[4].Value = employee.Grade.BasicAmt;
                employeeGridView.Rows[srl].Cells[5].Value = aGradeManager.GetMedicalAmount(employee.Grade);
                employeeGridView.Rows[srl].Cells[6].Value = aGradeManager.GetHouseRent(employee.Grade);
                employeeGridView.Rows[srl].Cells[7].Value = aGradeManager.CalculateTotalSalary(employee.Grade);

                totalSalary += aGradeManager.CalculateTotalSalary(employee.Grade);

                srl++;
            }

            totalSalaryextBox.Text = totalSalary.ToString();
        }
        private void gradeComboBox_SelectedIndexChanged(object sender, EventArgs e)
        {
            Grade aGrade = (Grade)gradeComboBox.SelectedItem;

            salaryTextBox.Text = aGradeManager.CalculateTotalSalary(aGrade).ToString();
        }