CODEWITHSUNDEEP
c#.netdata-bindingobservablecollectionasync-await
loop
loop

Reputation: 9242

ObservableCollection is not updating data

i am getting problem with the observablecollection because it is not updating my view. it is getting data in it i have checked it. i have also make event its collection changed event but it is also not getting called. i don't know why is this happening here is my code..

public async Task GetActivityStudentCollection()
    {

        StudentActivityCollection =  await ViewModelLocator.ActivityViewModel.GetActivity(0, 8, 0, 20);

        StudentActivityCollection.CollectionChanged += StudentActivityCollection_CollectionChanged;
   //     RaisePropertyChanged("StudentActivityCollection");
    }

    void StudentActivityCollection_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
      //  throw new NotImplementedException();
    }

i have bind this collection with listview like this.

 ActivityListViewSource.Source = ViewModelLocator.DashBoard.StudentActivityCollection;

this ViewModelLocator.ActivityViewModel.GetActivity(0, 8, 0, 20); method is returning a collection that is i have binded(not working) but if i binded the collection directly to the collection that is going to be return it works..means if i binded like this(it work)..

ActivityListViewSource.Source = ViewModelLocator.ActivityViewModel.ActivityCollection;

i am sorry for my bad english.please try to understand the problem. is it because of async method or what. any kind of help is appreciated..

Upvotes: 0

Views: 167

Answers (2)

samar
samar

Reputation: 5201

Try something like this

public async Task GetActivityStudentCollection()
{

    var studentActivityColl =  await ViewModelLocator.ActivityViewModel.GetActivity(0, 8, 0, 20);

    foreach(var studentAct in studentActivityColl)
        StudentActivityCollection.Add(studentAct);

    StudentActivityCollection.CollectionChanged += StudentActivityCollection_CollectionChanged;
//     RaisePropertyChanged("StudentActivityCollection");
}

Upvotes: 1

Jeroen van Langen
Jeroen van Langen

Reputation: 22038

You shouldn't return a new collection from that method. You should pass an instance.

ObservableCollection studentActivityCollection = new ObservableCollection();

studentActivityCollection.CollectionChanged += StudentActivityCollection_CollectionChanged;

await ViewModelLocator.ActivityViewModel.GetActivity(studentActivityCollection, 0, 8, 0, 20);

Because all events are fired before you registered your event on it.

Upvotes: 0

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