async Task ExecuteLoadItemsCommand()
{
// standard pattern to protect asynchronous functions
if (IsBusy)
{
return;
}
// if the work has started - no further attempts of the work can occur
IsBusy = true;
try
{
// look up necessary data and populate
Notes.Clear();
var notes = await PluralSightDataStore.GetNotesAsync();
foreach (var note in notes)
{
Notes.Add(note);
}
}
catch (Exception ex)
{
Debug.WriteLine(ex);
}
finally
{
IsBusy = false;
}
}
async Task ExeculeLoadNotesCommand()
{
if (IsBusy)
{
return;
}
IsBusy = true;
try
{
Notes.Clear();
var notes = await PluralSightDataStore.GetNotesAsync();
foreach (var note in notes)
{
Notes.Add(note);
}
}
catch (Exception ex)
{
Debug.WriteLine(ex);
}
finally
{
IsBusy = false;
}
}
public ItemsViewModel()
{
Title = "Browse";
Notes = new ObservableCollection <Note>();
LoadNotesCommand = new Command(async() => await ExeculeLoadNotesCommand());
// <Sender, ArgType>
MessagingCenter.Subscribe <ItemDetailPage, Note>(this, "SaveNote", async(sender, note) =>
{
Notes.Add(note);
await PluralSightDataStore.AddNoteAsync(note);
});
}
public ItemsViewModel()
{
Title = "Browse";
Notes = new ObservableCollection <Note>();
LoadItemsCommand = new Command(async() => await ExecuteLoadItemsCommand());
//MessagingCenter.Subscribe<type of the sender, type of the data you expect with the message>(reference to the class calling the subscribe method,
// string identifying the message,
// async lambda expression (reference to message sender, information sent with that message) => { work we want to get done when the message is sent});
MessagingCenter.Subscribe <ItemDetailPage, Note>(this, "SaveNote",
async(sender, note) => {
// note appear in list view - add note to note collection
Notes.Add(note); // note collection is an observable selection - autommatically updates list view
//save this into the data store
await PluralSightDataStore.AddNoteAsync(note);
});
//Handle Note Updates
MessagingCenter.Subscribe <ItemDetailPage, Note>(this, "UpdateNote",
async(sender, note) =>
{
await PluralSightDataStore.UpdateNoteAsync(note);
// modifying a memeber within an ObservableCollection does not autoatically refresh data binding
// we must explicity repopulate the collection
await ExecuteLoadItemsCommand();
});
/* MessagingCenter.Subscribe<NewItemPage, Item>(this, "AddItem", async (obj, item) =>
* {
* var newItem = item as Item;
* Items.Add(newItem);
* await DataStore.AddItemAsync(newItem);
* });*/
}
async void InitializeCourseList()
{
CourseList = await PluralSightDataStore.GetCoursesAsync();
}
