Entity Framework Context.Set().Local would not sync with Datagrid after calling LoadAsync

Question

Entity Framework Local property is an ObservableCollection and can be bind to lets say a datagrid. But its items do not update with call to LoadAsync, or do update actually but do not reflect into datagrid. Consider following example:

XAML

<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition />
    </Grid.RowDefinitions>
    <StackPanel Orientation="Horizontal">
        <Button Content="Load" Click="btnLoad_Click"/>
        <Button Content="LoadAsync" Click="btnLoadAsync_Click"/>
        <Button Content="SetDataSource" Click="btnSetDataSource_Click"/>
    </StackPanel>
    <DataGrid Name="grdTest" Grid.Row="1"/>
</Grid>

Code Behind

TestContext db = new TestContext();
public MainWindow()
{
    InitializeComponent();
}

private void Window_Loaded(object sender, RoutedEventArgs e)
{
   grdTest.ItemsSource = db.Suppliers.Local;
}

private void btnLoad_Click(object sender, RoutedEventArgs e)
{
    var beforQuery = db.Suppliers.Local;
    db.Suppliers.Load();
}

private void btnLoadAsync_Click(object sender, RoutedEventArgs e)
{
    var beforQuery = db.Suppliers.Local;
    db.Suppliers.LoadAsync();
}

private void btnSetDataSource_Click(object sender, RoutedEventArgs e)
{
    grdTest.ItemsSource = null;
    grdTest.ItemsSource = db.Suppliers.Local;
}

If I press Load button first, it behave as expected (load all items into collection and they are reflected into datagrid)
If I press LoadAsync button first, Only one item is loaded to Local items (which is another question, why only one item), but it is not reflected into datagrid, I can press SetDataSource to see that.
Each time I press LoadAsync only one item is added to the previous set!!
And If I press LoadAsync and then Load an error would come up and say "An ItemsControl is inconsistent with its items source"

Now my question is, how can I use LoadAsync and Local items properly? If I can not load items form database with LoadAsync method, then what is its use?

*Only one item is loaded to Local items* - Not very likely. Are you sure you check that after `LoadAsync` has finished? — Gert Arnold, Jul 14 '15 at 22:24
Yes, I am sure, but now with jjj answer it is working properly — mesmoll, Jul 15 '15 at 07:25

score 1 · Accepted Answer · edited May 23 '17 at 11:51

1

The problem is that the ItemsSource is being updated on a different thread than the control's thread. If you're using .NET 4.5, you can use EnableCollectionSynchronization to allow multiple threads to access a collection.

See this answer for an example.

edited May 23 '17 at 11:51

Community

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answered Jul 14 '15 at 18:12

jjj

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Entity Framework Context.Set().Local would not sync with Datagrid after calling LoadAsync

1 Answers1