title: Update a ViewModel when an item in an observable collection is updated
body: <p>Source code is here: 
  <a href="https://github.com/djangojazz/BubbleUpExample" rel="nofollow noreferrer">https://github.com/djangojazz/BubbleUpExample</a></p>
  
  <p>The problem is I am wanting an ObservableCollection of a ViewModel to invoke an update when I update a property of an item in that collection.  I can update the data that it is bound to just fine, but the ViewModel that holds the collection is not updating nor is the UI seeing it.</p>
  
  <pre><code>public int Amount
  {
    get { return _amount; }
    set
    {
      _amount = value;
      if (FakeRepo.Instance != null)
      {
        //The repo updates just fine, I need to somehow bubble this up to the 
        //collection's source that an item changed on it and do the updates there.
        FakeRepo.Instance.UpdateTotals();
        OnPropertyChanged("Trans");
      }
      OnPropertyChanged(nameof(Amount));
    }
  }
  </code></pre>
  
  <p>I basically need the member to tell the collection where ever it is called: "Hey I updated you, take notice and tell the parent you are a part of.  I am just ignorant of bubble up routines or call backs to achieve this and the limited threads I found were slightly different than what I am doing.  I know it could possible be done in many ways but I am having no luck.</p>
  
  <p>In essence I just want to see step three in the picture below without having to click on the column first. </p>
  
  <p><a href="https://i.stack.imgur.com/dj0k6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dj0k6.png" alt="enter image description here"></a></p>