/// <summary>
 /// when select nanny all the nanny details would automaticlly appear in the contract fieds
 /// </summary>
 /// <param name="sender"></param>
 /// <param name="e"></param>
 private void NannyDataGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {
     try
     {
         if (nanny != null)
         {
             contract = new BE.Contract();
             this.contract.ChildId     = (int)this.selectChildComboBox.SelectedValue;
             this.contract.NannyId     = nanny.Id;
             this.contract.MonthlyRate = nanny.MonthlyRate;
             this.contract.WeeklyHours = bl.CalculateContractWeeklyHours(contract);
             if (nanny.EnanblePayForHour == true)
             {
                 this.contract.HourlyRate = nanny.HourlyRate;
             }
             this.contractDetailsGrid.DataContext = contract;
             if (contract.PayPerHourOrMonth == BE.PaymentPer.Hour && contract.HourlyRate == null || selectChildComboBox.SelectedIndex < 0)
             {
                 return;
             }
             this.contract.NetoRate = bl.CalculateContractRate(contract);
         }
     }
     catch (Exception ex)
     {
         MessageBox.Show(ex.Message);
     }
 }