Binding Issues on Xamarin forms about xamarin-forms-tab-badge

[jmblargent]

If you are binding to the TabbedPage ViewModel, you need to specify the source and path for the binding. In your first example, if your TabbedPage is named Tabs, then the binding would look like {Binding Source={x:Reference Tabs}, Path=BindingContext.Count}. If you don't set the source, then it is looking for Count in the binding context of Page1.

[mohammedmsadiq]

i also tried the implementation on your sample project and property is not detected any changes. see below;

public class MasterTabbedPageViewModel : ViewModelBase, INotifyPropertyChanged
{
readonly INotificationService notificationService;

    public MasterTabbedPageViewModel(INavigationService navigationService, INotificationService notificationService, IPageDialogService pageDialogService, IProfilePictureService profilePictureService, IDeviceService deviceService, IEventAggregator eventAggregator, IAnalyticsService analyticsService) : base(navigationService, pageDialogService, profilePictureService, deviceService, eventAggregator, analyticsService)
    {
        Title = "MasterTabbedPage";
        this.notificationService = notificationService;           
    }

    public override void OnAppearing()
    {
        this.ExecuteAsyncTask(async () =>
        {
            var item = await this.notificationService.GetNotificationCount();
            courseCount = item.NewCourseCount;
            taskCount = item.TaskCount;
        });
        base.OnAppearing();
    }

    private int courseCount;

    public string CourseCount => courseCount <= 0 ? string.Empty : courseCount.ToString();

    public int CourseCountValue
    {
        get => courseCount;
        set
        {
            if (courseCount == value)
                return;

            courseCount = value;
            RaisePropertyChanged(nameof(CourseCountValue));
            RaisePropertyChanged(nameof(CourseCount));
        }
    }

    private int taskCount;

    public string TaskCount => taskCount <= 0 ? string.Empty : taskCount.ToString();

    public int TaskCountValue
    {
        get => taskCount;
        set
        {
            if (taskCount == value)
                return;

            taskCount = value;
            RaisePropertyChanged(nameof(TaskCountValue));
            RaisePropertyChanged(nameof(TaskCount));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void RaisePropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

}