Silverlight - MVVM: Datagrid bound to ICollectionView filled with "ChildViewModel" wont refresh data

Question

I couldn't find a similar case yet and so I struggle on. I'm quite a greenhorn with Silverlight and struggle with the refresh of a ICollectionView. The Refresh-Method won't actually refresh the data in my datagrid although they're changed (see it in debugger and after sorting the datagrid a few times it will finally reflect the changes). I'm afraid I completely messed up the whole construct of my application. I think the problem is somehow related to my "MainViewModel-ChildViewModel" princip I implemented.

Here is my construct: In my Main Page i added a "Main Viewmodel" as resource.

<UserControl.Resources>
        <vm:WorkingBasketViewModel x:Key="VMMain"/>
</UserControl.Resources>

the Grid LayoutRoot then sets it's datacontext to this viewmodel:

<Grid x:Name="LayoutRoot" DataContext="{StaticResource VMMain}" Margin="20">
........// all the content
</Grid>

In the "Main Viewmodel" I define a ObservableCollection which holds the data that will be displayed in a datagrid in form of a CollectionViewSource. the ObservableCollection items are based on a "ChildViewModel" that represents the actual data and it's logic for each datarow. Means: Each item that is added to the ObservableCollection is of the type of the "ChildViewModel". I designed it that way because I am going to display several "detail-pages" (based on chosen Function or on double click of a cell) that will then allow to view, modify and work on the data in another usercontrol. Direct modification in the datagrid is not allowed. That way around I only need to pass the childviewmodel to the next page (or usercontrol) and the data and its logic are passed on.

private readonly ObservableCollection<childViewModel> _requestList = new ObservableCollection<childViewModel>(); // saves list of "childviewmodel-items"
private readonly ICollectionView _requestCollectionView; // ICollectionView for _requestlist-Collection.

// In the contstructor of the "Main Viewmodel"
var cvs = new CollectionViewSource {Source = _requestList};
                    cvs.SortDescriptions.Add(new SortDescription("RPI_Priority", ListSortDirection.Ascending));
                    cvs.SortDescriptions.Add(new SortDescription("REQ_TestingDate", ListSortDirection.Ascending));
                    _requestCollectionView = cvs.View; 
LoadData(); // db-fetch (entity framework)



/// <summary>
/// Binding to DataGrid!
/// </summary>
public ICollectionView Requests //-> BINDING TO DATAGRID!
{
    get
        {
            return _requestCollectionView;
        }
}

In the Completed eventhandler of the db-fetch fill the observablecollection with the childviewmodel

private void requests_requestLoadingComplete(object sender, EntityResultsArgs<REQ_Request> e)
{
    if (!e.HasError)
    {

       //Fire Event on UI Thread
       Application.Current.RootVisual.Dispatcher.BeginInvoke(() =>
       {
            var o = e.Results.OrderBy(r => r.REQ_TestingDate);
            //clear request list
            _requestList.Clear();
            // add requests to collectionview
            foreach (REQ_Request r in o)
            {
                   // for each record generate a Childviewmodel entry and add it to the observable collection
                   _requestList.Add(new childviewmodel(r));
            }

        });
       }
       else
       {
           // notify if there is any error
           reportError(this,new ResultsArgs(e.Error));
       }

RaiseVMStateChanged();
}

I further have a datagrid on the mainpage that is bound to this ICollectionView. The itemsource is to the list of "ChildViewModel". It's Properties are bound it:

<sdk:DataGrid AutoGenerateColumns="False" Grid.Row="1" ItemsSource="{Binding Path=Requests}" SelectionMode="Single">
    <sdk:DataGrid.Columns>
        <sdk:DataGridTextColumn Header="ID" Binding="{Binding REQ_ID}" Width="40" IsReadOnly="true"/>
        <sdk:DataGridTextColumn Header="Applikationsname" Binding="{Binding REQ_ApplicationName}" Width="250" IsReadOnly="true"/>
        <sdk:DataGridTextColumn Header="Typ" Binding="{Binding RET_Type}"  Width="70" IsReadOnly="true"/>
        <sdk:DataGridTextColumn Header="Prio" Binding="{Binding RPI_Priority}" Width="70" IsReadOnly="true" />
        <sdk:DataGridTextColumn Header="Status" Binding="{Binding RST_Status}" Width="70" IsReadOnly="true"/>
        <sdk:DataGridTextColumn Header="Sprache" Binding="{Binding SWL_Language}" Width="70" IsReadOnly="true"/>
        <sdk:DataGridTextColumn Header="Version" Binding="{Binding REQ_Version}" Width="70" IsReadOnly="true"/>
        <sdk:DataGridTextColumn Header="Betriebssystem" Binding="{Binding SOS_OS}" Width="150" IsReadOnly="true"/>
        <sdk:DataGridTextColumn Header="DA" Binding="{Binding Dienstabteilungen}" Width="150" IsReadOnly="true"/>
        <sdk:DataGridTextColumn Header="AV" Binding="{Binding AV_Fullname}"  Width="150" IsReadOnly="true"/>
        <sdk:DataGridTextColumn Header="Paketierer" Binding="{Binding Paketierer_Fullname}"  Width="150" IsReadOnly="true"/>
        <sdk:DataGridTextColumn Header="Paketierer QS" Binding="{Binding PaketiererQS_Fullname}" Width="150" IsReadOnly="true" />
        <sdk:DataGridTextColumn Header="Abnahmetermin" Binding="{Binding REQ_TestingDate}" Width="150" IsReadOnly="true" />
    </sdk:DataGrid.Columns>
</sdk:DataGrid>

Now all of this works fine and smoothly. On click of a Function-Button I open another usercontrol that is initialised with an instanze of the "Childviewmodel" or an inherit of it. (with some function that is a childwindow with some other function it shows a usercontrol that displays all the details etc)

for example childwindow:

ShowChildWindow(new PkgRequestDataControl(_vm.CurrentRequest)); --> PkgRequestDataControl inherits from childviewmodel. _vm.CurrentRequest is one single instance of "childviewmodel" that is given

Now I modify the date in this childwindow an return to the mainpage. On return I call refresh on the collectionView (Requests.Refresh();) -> But the data won't refresh. Well..sometimes it does but most of the time it does not until i sorted the changed coloum of the datagrid 2-3 times (click on the header to sort und sort..and sort)

What am I doing wrong? Anybody can help out? Is the whole construct messy?

Cheers Elime

Answer 1

I'm not sure exactly which implementation of ICollectionView you're using, but in general ICollectionView.Refresh() only refreshes the View property taking filtering, sorting and grouping into account. For your UI to realize this change, you still need to implement INotifyPropertyChanged and raise a PropertyChanged event after calling Refresh().