Save Edit Update Xamarin

Question

I have 2 pages one is master other detail page.

 

detailpage.xaml

<ContentPage.ToolbarItems>
<ToolbarItem Icon="plus.png" Text="Add" Activated="OnAdd" Order="Primary"/>
</ContentPage.ToolbarItems>
<ListView x:Name="iList" ItemSelected="IList_ItemSelected" >
<ListView.ItemTemplate>
<DataTemplate>
<TextCell Text="{Binding ExpenseCategory}" Detail="{Binding ExId}" >
<TextCell.ContextActions>
<MenuItem Text="Delete"
IsDestructive="True"
Clicked="MenuItem_Clicked"
CommandParameter="{Binding .}" />
</TextCell.ContextActions>
</TextCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>

detailpage.xaml.cs

public event EventHandler<Expense> ExpenseAdded;
public event EventHandler<Expense> ExpenseUpdated;
private SQLiteAsyncConnection _connection;
public ExpenseDetail (Expense addexpense)
{
if (addexpense == null)
throw new ArgumentNullException(nameof(addexpense));
InitializeComponent();
_connection = DependencyService.Get<ISQLiteDb>().GetConnection();
BindingContext = new Expense
{
ExId = addexpense.ExId,
ExpenseCategory = addexpense.ExpenseCategory,
Amount=addexpense.Amount,
ItemName=addexpense.ItemName,
Exdate=addexpense.Exdate
};
}
protected async override void OnAppearing()
{
var pick = await _connection.Table<ExpenseCatMaster>().ToListAsync();
expenseList.ItemsSource = pick;
expenseList.ItemDisplayBinding = new Binding("ExCategory");
base.OnAppearing();
}
private async void OnSave(object sender, EventArgs e)
{
var expense = new Expense
{
ExpenseCategory = expenseList.Items[expenseList.SelectedIndex].ToString(),
SelectedIndex = expenseList.SelectedIndex,
// SubCategory= subList.Items[subList.SelectedIndex].ToString(),
ItemName=itemName.Text,
Amount = Convert.ToDecimal(amount.Text),
Exdate=datepick.Date
};
await _connection.InsertAsync(expense);
await Navigation.PopAsync();
}

after saving the detils .. it will appear in master page

 

when i click the iteam we want to change ie,In edit mode , picker doesnot display the selected item

 

and now when i click save button i ahve to update existing data . Dont create new fields in table.

 

masterpage.xaml

<ContentPage.ToolbarItems>
<ToolbarItem Icon="plus.png" Text="Add" Activated="ToolbarItem_Activated" Order="Primary"/>
</ContentPage.ToolbarItems>
<ListView x:Name="iList" ItemSelected="ListView_ItemSelected">
<ListView.ItemTemplate>
<DataTemplate>
<TextCell Text="{Binding Amount}" Detail="{Binding InId}" >
<TextCell.ContextActions>
<MenuItem Text="Delete"
IsDestructive="True"
Clicked="MenuItem_Clicked"
CommandParameter="{Binding .}" />
</TextCell.ContextActions>
</TextCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>

masterpage.xaml.cs

public partial class AddExpense : ContentPage
{
private ObservableCollection<Expense> _income;
private SQLiteAsyncConnection _connection;
private bool _isDataLoaded;
public AddExpense ()
{
InitializeComponent ();
_connection = DependencyService.Get<ISQLiteDb>().GetConnection();
}
protected async override void OnAppearing()
{
if (_isDataLoaded)
return;
_isDataLoaded = true;
await LoadData();
base.OnAppearing();
}
private async Task LoadData()
{
await _connection.CreateTableAsync<Expense>();
var incomeTab = await _connection.Table<Expense>().ToListAsync();
_income = new ObservableCollection<Expense>(incomeTab);
iList.ItemsSource = _income;
}
private async void OnAdd(object sender, EventArgs e)
{
var page = new ExpenseDetail(new Expense());
page.ExpenseAdded += (source, expense) =>
{
_income.Add(expense);
};
await Navigation.PushAsync(page);
}
private async void IList_ItemSelected(object sender, SelectedItemChangedEventArgs e)
{
if (iList.SelectedItem == null)
return;
var selectIncome = e.SelectedItem as Expense;
iList.SelectedItem = null;
var page = new ExpenseDetail(selectIncome);
//page.ExpenseUpdated += (source, expense) =>
//{
// selectIncome.ExId = expense.ExId;
// selectIncome.ExpenseCategory = expense.ExpenseCategory;
// selectIncome.ItemName = expense.ItemName;
// selectIncome.Exdate = expense.Exdate;
// selectIncome.Amount = expense.Amount;
//};
await Navigation.PushAsync(page);
}
private async void MenuItem_Clicked(object sender, EventArgs e)
{
var income = (sender as MenuItem).CommandParameter as Expense;
if (await DisplayAlert("Warning", $"Are you sure you want to delete {income.ExpenseCategory}?", "differentiate
{
_income.Remove(income);
await _connection.DeleteAsync(income);
}
}
}

Please Help. How will i differenciate update and save