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View Model Helper Class

As per .NET and Xamarin Forms guidelines, ViewModels usually implement the INotifyPropertyChanged interface to inform the view of changes to the data model. This involves a lot of boilerplate, so VertiGIS Studio Mobile has a class, NotifyPropertyBase, which handles the boilerplate and simplifies your code.

The ViewModel of the progress bar custom component is a good example of this pattern.

using App1.Components;using VertiGIS.Mobile.Composition;using VertiGIS.Mobile.Composition.Views;
[assembly: ViewModel(typeof(ProgressBarComponentViewModel))]namespace App1.Components{    public class ProgressBarComponentViewModel : NotifyPropertyBase    {        private double _progress = 0;
        private bool _workComplete = false;
        public double Progress        {            get => _progress;            set => SetProperty(ref _progress, value);        }
        public bool WorkComplete        {            get => _workComplete;            set            {                SetProperty(ref _workComplete, value);                OnPropertyChanged(nameof(WorkNotComplete));            }        }
        public bool WorkNotComplete => !WorkComplete;    }}

NotifyPropertyBase implements INotifyPropertyChanged for you and provides a helper function, SetProperty. This helper function will ensure that OnPropertyChanged is called if the value has changed and that the underlying field is set.

Relevant SDK Sample#

The VertiGIS Studio Mobile SDK Samples has an example of a breadcrumbs component that uses a viewmodel.