Listview is not updating when viewmodel object changes

Question

<?xml version="1.0" encoding="UTF-8" ?>
<ContentPage
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="AudioDigestMembership.Views.MainContent.Filter.FilterPageDetail"
Shell.NavBarHasShadow="False"
Shell.NavBarIsVisible="True"
xmlns:ios="clr-namespace:Xamarin.Forms.PlatformConfiguration.iOSSpecific;assembly=Xamarin.Forms.Core" xmlns:autocomplete="clr-namespace:Syncfusion.SfAutoComplete.XForms;assembly=Syncfusion.SfAutoComplete.XForms"
ios:NavigationPage.IsNavigationBarTranslucent="true"
ios:Page.UseSafeArea="true"
BackgroundColor="{AppThemeBinding Light=#FFFFFF, Dark=#121212}"
xmlns:ListCollection="clr-namespace:System.Collections.Generic;assembly=netstandard" xmlns:controls="clr-namespace:AudioDigestMembership.Controls" xmlns:xforms="clr-namespace:Syncfusion.ListView.XForms;assembly=Syncfusion.SfListView.XForms" xmlns:converter="clr-namespace:AudioDigestMembership.Converters"
>
<ContentPage.Resources>
<ResourceDictionary>
<converter:SelectionBoolToImageConverter x:Key="BoolToImageConverter" />
</ResourceDictionary>
</ContentPage.Resources>
<ContentPage.Content>
<Grid RowDefinitions="44, 1*">
<autocomplete:SfAutoComplete x:Name="autoComplete"
Grid.Row="0"
BorderColor="{AppThemeBinding Light=#000, Dark=#fff}"
ShowBorder="True"
Watermark="Search by name, specialty, topic"
WatermarkColor="{AppThemeBinding Light=#386384, Dark=#f6f6f6}"
TextColor="{AppThemeBinding Light=#386384, Dark=#f6f6f6}"
TextSize="15" >
<autocomplete:SfAutoComplete.AutoCompleteSource>
<ListCollection:List x:TypeArguments="x:String">
<x:String>India</x:String>
<x:String>Uganda</x:String>
<x:String>Ukraine</x:String>
<x:String>Canada</x:String>
<x:String>United Arab Emirates</x:String>
<x:String>France</x:String>
<x:String>United Kingdom</x:String>
<x:String>China</x:String>
<x:String>United States</x:String>
<x:String>Japan</x:String>
<x:String>Angola</x:String>
</ListCollection:List>
</autocomplete:SfAutoComplete.AutoCompleteSource>
</autocomplete:SfAutoComplete>

        <controls:MyListView
                Grid.Row="1"
                x:Name="listView"
                VerticalOptions="FillAndExpand"
                HorizontalOptions="FillAndExpand"
                ItemsSource="{Binding DetailModel, Mode=TwoWay}"
                BackgroundColor="{AppThemeBinding Light=#FFFFFF, Dark=#121212}"
                SelectionMode="Multiple"
                SelectionBackgroundColor="{AppThemeBinding Light=#FFFFFF, Dark=#121212}"
                ItemTapped="listView_ItemTapped"
                AutoFitMode="Height"
                ItemSize="50"
            >
            <controls:MyListView.ItemTemplate>
                <DataTemplate>
                    <Grid RowDefinitions="*, 1" VerticalOptions="FillAndExpand"
                          HorizontalOptions="FillAndExpand" x:Name="MultiSelectCellGrid">
                        <Grid Padding="20, 20" Grid.Row="0" ColumnSpacing="20" ColumnDefinitions="30, *"
                              VerticalOptions="FillAndExpand"
                              HorizontalOptions="FillAndExpand">
                            <Image Grid.Column="0"
                                    Source="{Binding IsSelected, Converter={StaticResource BoolToImageConverter}}"/>
                            <Label  Grid.Column="1"
                                    Text="{Binding SpecialtyName}"
                                   TextColor="{AppThemeBinding Light=#121212, Dark=#FFFFFF}"
                                   VerticalOptions="FillAndExpand"
                                   HorizontalOptions="FillAndExpand"
                                   VerticalTextAlignment="Center"
                                   HorizontalTextAlignment="Start"
                               />
                        </Grid>
                        <BoxView Grid.Row="1" Margin="0" BackgroundColor="{AppThemeBinding Light=#D4DDE5, Dark=#585858}" />
                    </Grid>
                </DataTemplate>
            </controls:MyListView.ItemTemplate>
        </controls:MyListView>
    </Grid>
</ContentPage.Content>

</ContentPage>

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using ApiSDK;
using AudioDigestMembership.Utils;
using AudioDigestMembership.ViewModels.Library.FilterandSort;
using Xamarin.Essentials;
using Xamarin.Forms;

namespace AudioDigestMembership.Views.MainContent.Filter
{
public partial class FilterPageDetail : ContentPage
{
FilterPageDetailViewModel ViewModel = new FilterPageDetailViewModel();
public FilterPageDetail()
{
InitializeComponent();
this.BindingContext = this.ViewModel;
}

    protected override void OnAppearing()
    {
        base.OnAppearing();
        ViewModel.OnAppearing();
    }

    protected override void OnDisappearing()
    {
        ViewModel.OnDisappearing();
        base.OnDisappearing();
    }

    private async void listView_ItemTapped(object sender, Syncfusion.ListView.XForms.ItemTappedEventArgs e)
    {
        try
        {
            var viewModel = (SpecialtyDetail)e.ItemData;
            viewModel.IsSelected = !viewModel.IsSelected;
            viewModel.SpecialtyName = "test";
            int index = this.ViewModel.DetailModel.IndexOf(viewModel);
            var updateList = this.ViewModel.DetailModel;
            updateList[index] = viewModel;
            listView.ItemsSource = new ObservableCollection<SpecialtyDetail>() { viewModel };
            //updateList.Clear();
            //this.ViewModel.DetailModel = new ObservableCollection<SpecialtyDetail>() { viewModel };
        }
        catch (Exception ex)
        {
            await App.Current.MainPage.DisplayAlert("Alert", ex.Message, "OK");
        }
    }
}

}

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Web;
using System.Windows.Input;
using ApiSDK;
using AudioDigestMembership.Interfaces;
using AudioDigestMembership.Models;
using Newtonsoft.Json;
using Xamarin.Forms;

namespace AudioDigestMembership.ViewModels.Library.FilterandSort
{
public class FilterPageDetailViewModel: BaseViewModel
{
public ICommand ListItemTappedCommand { protected set; get; }
private ObservableCollection<SpecialtyDetail> detailModel;
public ObservableCollection<SpecialtyDetail> DetailModel
{
set
{
detailModel = value;
OnPropertyChanged();
}
get
{
return detailModel;
}
}

    public FilterPageDetailViewModel()
    {
        ListItemTappedCommand = new Command(async (parameter) =>
        {
            Console.WriteLine(parameter);
        });
    }

    public void OnAppearing()
    {
        this.FetchSpecialities();
    }

    public void OnDisappearing()
    {

    }


    public async void FetchSpecialities()
    {
        DependencyService.Get<ILodingPageService>().ShowLoadingPage();
        try
        {
            this.DetailModel = await _mobileApi.GetAllSpecialties();
        }
        catch (Exception ex)
        {
            await App.Current.MainPage.DisplayAlert("Alert", ex.Message, "OK");
        }
        DependencyService.Get<ILodingPageService>().HideLoadingPage();
    }
    //public void ApplyQueryAttributes(IDictionary<string, string> query)
    //{
    //    // The query parameter requires URL decoding.
    //    this.DetailModel = JsonConvert.DeserializeObject<FIlterModel>(HttpUtility.UrlDecode(query["DetailItemModel"]));
    //}

}

}

I tried changing viewmodel object - DetailModel in listview tap event. But it is not updating in listview

i even changed DetailModel parameters but it is not updating to new parameters