topic Re: Updating View with MVVM in Revit API Forum

Updating View with MVVM

retug_austin — Sun, 31 Mar 2024 20:52:15 GMT

I made a recent post here about MVVM and keeping a list of selected elements updated with updates in the Revit model.

I have made some progress after the guidance provided in that first post, but still running into an issue I can't seem to resolve. After some review, it seemed like IUpdater interface would be the best way to keep my view up to date with the revit model changes. Full code on github.

Debugging in the Execute command, the model elements are correctly revised based on updates in performed in the revit model (see if gif below, one of the items changes from a W18x40 to a W21x44, the list of IEnumerable<RevitFramingModel> structuralFramingElements is correctly updated while debugging)

The problem, the datagrid view is not updated with this data.

Do you know where my problem is? I can't figure out why the view won't update.

Thanks!

Re: Updating View with MVVM

scgq425 — Mon, 01 Apr 2024 06:43:33 GMT

Hi @retug_austin :

i download u code and debug this , if u want changed type and trigged the window , need to change the code to this , also can add this code `d:DataContext="{d:DesignInstance Type = local:MainViewModel}"` to u mainwindow xaml , this is easy ,so i not push this code to u github .

```

public class MainViewModel : INotifyPropertyChanged{

private ObservableCollection<RevitFramingModel> _structuralFramingElements = new ObservableCollection<RevitFramingModel>();

public ObservableCollection<RevitFramingModel> StructuralFramingElements
{
get { return _structuralFramingElements; }
set
{
_structuralFramingElements = value;
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(StructuralFramingElements)));
}
}

}

```

Re: Updating View with MVVM

retug_austin — Mon, 01 Apr 2024 13:42:13 GMT

Thanks a ton @scgq425 , this worked.

May I ask, why did you switch from IEnumerable to ObservableCollection on _stucturalFramingElements and StructuralFramingElements?

So cool seeing these sync'd up:

Re: Updating View with MVVM

ricaun — Mon, 01 Apr 2024 14:56:15 GMT

When working with 'Binding' and a list of objects, it is better to use the 'ObservableCollection'.

The 'ObservableCollection' has the 'INotifyPropertyChanged' and 'INotifyCollectionChanged', if you add or remove an element by default the UI gonna be updated.