How to delete items from a collection view in xamarin.forms?

Question

NOTE: this didn't work : SQLite Error: Cannot delete WhereListIterator`1: it has no PK (Adding a table name made no change)

I have an AcceuilPage which basically do this : https://github.com/devcrux/Xamarin.Forms-Expander but i added a delete icon and when i press it i want to be able to delete all the content for this date ( also the date) from this page.

So i added a delete function to delete it from database but when i expand for a date and press delete i get this error : Exception: System.NotSupportedException: Cannot delete Object: it has no PK which bring me to await App.Database.DeleteAgendaAsync(agenda); in :

async void DeleteButtonClicked(object sender, EventArgs e)
{
    
    var agenda = (Agenda)AgendaCollection.SelectedItem;

    await App.Database.DeleteAgendaAsync(agenda);
    await Navigation.PopAsync();

}

i also tried for the error line this : await App.Database.DeleteAgendaAsync(agenda); but this didn't even do anything when i pressed it ( no error and nothing happening).

I saw that this was a working fine for a listview but im struggling to do it in a collectionview, feels to me like it doesn't know if i am currently selecting something. ( With listview, when u click an item, the item view change color).

What am i doing wrong, im also starting to think that using a listview would be more simple.

My AcceuilPage.xaml

My AcceuilPage.xaml.cs

using Calculette.ViewModel;
using Calculette.Models;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using Xamarin.Forms.PancakeView;

namespace Calculette
{
    public partial class MainPage : TabbedPage
    {
        public MainPage()
        {
            InitializeComponent();
            BindingContext = new Agenda();

        }
        protected async void GoToFormPage(object sender, EventArgs e)
        {
            await Navigation.PushAsync(new Views.AgendaItemDetailPage());
        }
        protected async void GoToNewFormPage(object sender, EventArgs e)
        {
            await Navigation.PushAsync(new Views.NewFormPage());
        }


        async void DeleteButtonClicked(object sender, EventArgs e)
        {
            
            var agenda = (Agenda)BindingContext;

            await App.Database.DeleteAgendaAsync(agenda);
            await Navigation.PopAsync();

        }

        protected override async void OnAppearing()
        {
           base.OnAppearing();
            AgendaCollection.ItemsSource = await App.Database.GetAgendasAsync();
        }
    }

}

AgendaDatabase.cs

using System;
using System.Collections.Generic;
using System.Text;
using SQLite;
using Calculette.Models;
using System.Threading.Tasks;

namespace Calculette.Database
{
    public class AgendaDatabase
    {
        readonly SQLiteAsyncConnection database;

        public AgendaDatabase(string dbPath)
        {
           
            database = new SQLiteAsyncConnection(dbPath);
            database.CreateTableAsync().Wait();
        


        }

        // Get all agenda
        public Task> GetAgendasAsync()
        {
            return database.Table().ToListAsync();
        }

        // Get specific agenda
        public Task GetAgendaAsync(int id)
        {
            return database.Table()
                            .Where(i => i.ID == id)
                            .FirstOrDefaultAsync();
        }

        // Insert new agenda (save)
        public Task SaveAgendaAsync(Agenda agenda)
        {
            if (agenda.ID != 0)
            {
                return database.UpdateAsync(agenda);
            }
            else
            {
                return database.InsertAsync(agenda);
            }
        }
        
        //Delete specific agenda
        public Task DeleteAgendaAsync(Agenda agenda)
        {
            return database.DeleteAsync(agenda);
        }
    }
}

Agenda.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Text;
using SQLite;
using Calculette.Database;

namespace Calculette.Models
{
    [Table("Agenda")]
    public class Agenda
    {
        [PrimaryKey, AutoIncrement]
        public int ID { get; set; }
        public string Topic { get; set; }
        public string Duration { get; set; }
        public DateTime Date { get; set; }

    }
}

ColeX · Accepted Answer

When we touch on the imagebutton/button , the click event triggers , but it does not mean we select an item in CollectionView ,the button click event covers the click/tap event on item of Collectionview itself, so in this scenario , AgendaCollection.SelectedItem is null ,then the error happens .

For the second approach you used: var agenda = (Agenda)BindingContext; , you set BindingContext in constructor : BindingContext = new Agenda(); , BindingContext is a brand new object which is not the one you are selecting .

To solve the prorblem , you could get the imagebutton's BindingContext and then manipulate the logic .

 async void DeleteButtonClicked(object sender, EventArgs e)
    {
        
        ImageButton button = sender as ImageButton;
        var agenda = button.BindingContext as Agenda;

        await App.Database.DeleteAgendaAsync(agenda);
        await Navigation.PopAsync();

    }

Update

   public ObservableCollection GetAgendasAsync()
    {
        Listlist = database.Table().ToListAsync().Result;
        ObservableCollection result = new ObservableCollection(list);

        return result;
    }

How to delete items from a collection view in xamarin.forms?

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