Now we move on to the last view-model in our application. Add a new file called StockItemDetailsPageViewModel to our ViewModels folder in the Stocklist.Portable project.

Let's start by implementing the private properties:

#region Private Properties 
 
        private readonly IStocklistWebServiceController _stocklistWebServiceController; 
 
        private int _id; 
 
        private string _name; 
 
        private string _category; 
 
        private decimal _price; 
 
        private bool _inProgress; 
        
#endregion 

You should be able to add the public properties yourself. Here is the first to get you started:

public int Id 
        { 
            get 
            { 
                return _id; 
            } 
 
            set 
            { 
                if (value.Equals(_id)) 
                { 
                    return; 
                } 
 
                _id = value; 
                OnPropertyChanged("Id"); 
            } 
        } 

Now we need to add the LoadAsync function, which will use StocklistWebServiceController to pull the data from our API for a specific StockItem. Notice the use of the InProgress property, this is used to track the loading progress; as we are downloading in the background we want to display this progress to the user interface via an ActivityIndicator:

#region Methods 
 
        protected override async Task LoadAsync(IDictionary<string, object> parameters) 
        { 
            InProgress = true; 
 
            if (parameters.ContainsKey("id")) 
            { 
                Id = (int)parameters["id"]; 
            } 
 
            var contract = await _stocklistWebServiceController.GetStockItem(Id); 
 
            if (contract != null) 
            { 
                this.Name = contract.Name; 
                this.Category = contract.Category; 
                this.Price = contract.Price; 
            } 
 
            InProgress = false; 
        } 
 
        #endregion 

Then we add our constructor which will pull out the registered IoC objects and assign our private properties accordingly:

#region Constructors 
 
        public StockItemDetailsPageViewModel(INavigationService navigation, IStocklistWebServiceController stocklistWebServiceController, 
            Func<Action, ICommand> commandFactory) : base(navigation) 
        { 
            _stocklistWebServiceController = stocklistWebServiceController; 
        } 
 
        #endregion  

Finally, we need to register the view-model in the CommonModule:

builer.RegisterType<StockItemDetailsPageViewModel>().InstancePerDependency(); 

Add the extra enum for the StockItemDetailsPage to PageEnums.cs:

public enum PageNames 
    { 
        MainPage, 
 
        StocklistPage, 
 
        StockItemDetailsPage 
    } 

And add the extra switch case to NavigationService:

case PageNames.StockItemDetailsPage: 
                    return IoC.Resolve<Func<StockItemDetailsPage>>()();