postsharp observablecollection firing collectionchanged on propertychanged - wpf

Question

Non MVVM.
I got this ObservableCollection machines which is made of Machine-type objects:
[Serializable]
[NotifyPropertyChanged]
public abstract class Machine
{
public MachineNames MachineType { get; set; }
public int MachineVersion { get; set; }
public string LatestEditorName { get; set; }
public DateTime LatestSaveTime { get; set; }
public ObservableCollection<Parameter> Parameters { get; set; }
public string Notes { get; set; }
public abstract double CalculateThroughPut();
public Machine()
{
string[] nameParts = this.GetType().Name.Split('_');
Enum.TryParse(nameParts[0], out MachineNames currentMachineType);
MachineType = currentMachineType;
MachineVersion = int.Parse(nameParts[1]);
Parameters = new ObservableCollection<Parameter>();
ICollectionView icv = CollectionViewSource.GetDefaultView(Parameters);
icv.GroupDescriptions.Add(new PropertyGroupDescription("Group"));
LatestEditorName = Environment.UserName;
LatestSaveTime = DateTime.Now;
}
public double getValue(string parameterName)
{
Parameter currentParameter = Parameters.Where(x => x.Name == parameterName).First();
return currentParameter.Value * currentParameter.MetricConversionFactor;
}
And here's the declaration of it:
public partial class MainWindow : MetroWindow
{
IEnumerable<string> namesOfExistingMachines { get; set; }
public ObservableCollection<Machine> machines { get; set; }
and later on:
private void InitializeData()
{
machines = new ObservableCollection<Machine>();
this.DataContext = machines;
tcMainTabControl.ItemsSource = machines;
Notice please the [NotifyPropertyChanged] tag which is part of PostSharp, and simply makes all the properties of Machine changenotifiable for binding. in addition it makes all the properties of the properties changenotifiable.
Here's the initial window part of the XAML:
<Grid>
<Controls:MetroAnimatedTabControl Name="tcMainTabControl">
<TabControl.ItemContainerStyle>
<Style TargetType="TabItem">
<Setter Property="ToolTipService.ShowDuration" Value="100000"/>
<Setter Property="ToolTipService.InitialShowDelay" Value="0"/>
<Setter Property="Header" Value="{Binding Converter={StaticResource tabHeaderConverter}}"/>
<Setter Property="ToolTip">
<Setter.Value>
<StackPanel Orientation="Vertical">
<TextBlock HorizontalAlignment="Center" Margin="0,10" FontSize="40" FontWeight="Bold" Text="{Binding Path=MachineType}"/>
<Image HorizontalAlignment="Center" Source="{Binding Path=MachineType, Converter={StaticResource imageUriConverter}}"/>
<StackPanel HorizontalAlignment="Center" Margin="0,10" Orientation="Horizontal">
<TextBlock FontSize="20" Text="Throughput model version "/>
<TextBlock FontSize="20" Text="{Binding Path=MachineVersion}"/>
</StackPanel>
<StackPanel HorizontalAlignment="Center" Margin="0,10" Orientation="Horizontal">
<TextBlock FontSize="20" Text="created by "/>
<TextBlock FontSize="20" Text="{Binding Path=LatestEditorName}"/>
<TextBlock FontSize="20" Text=" on "/>
<TextBlock FontSize="20" Text="{Binding Path=LatestSaveTime, StringFormat=dd/MM/yyyy}"/>
</StackPanel>
<TextBlock Margin="0,10" FontSize="20" Text="{Binding Path=Notes}"/>
</StackPanel>
</Setter.Value>
</Setter>
</Style>
</TabControl.ItemContainerStyle>
<Controls:MetroAnimatedTabControl.ContentTemplate>
<DataTemplate>
<DockPanel LastChildFill="True" Margin="10,0">
<StackPanel Orientation="Vertical">
<Border BorderBrush="{DynamicResource AccentColorBrush}" BorderThickness="1,1,1,1" CornerRadius="8,8,8,8" Margin="0,20" HorizontalAlignment="Center">
<StackPanel Orientation="Horizontal" Margin="5">
<TextBlock FontSize="20" Text="Throughput: "/>
<TextBlock FontSize="20" Text="{Binding Converter={StaticResource throughputCalculationConverter}, UpdateSourceTrigger=PropertyChanged}"/>
<TextBlock FontSize="20" Text=" panel sides per hour"/>
</StackPanel>
</Border>
<ListView DockPanel.Dock="Left" ScrollViewer.VerticalScrollBarVisibility="Auto" ItemsSource="{Binding Path=Parameters, UpdateSourceTrigger=PropertyChanged}">
<ListView.GroupStyle>
<GroupStyle>
<GroupStyle.ContainerStyle>
<Style TargetType="{x:Type GroupItem}">
<Setter Property="Margin" Value="0,0,0,5"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type GroupItem}">
<Expander IsExpanded="True" BorderBrush="Black" BorderThickness="0,0,0,1">
<Expander.Header>
<TextBlock FontSize="20" FontWeight="Bold">
<Run>Discipline: </Run>
<TextBlock Text="{Binding Path=Name, Converter={StaticResource titleCaseConverter}}"/>
</TextBlock>
</Expander.Header>
<Expander.Content>
<Border Margin="2" CornerRadius="3">
<ItemsPresenter />
</Border>
</Expander.Content>
</Expander>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</GroupStyle.ContainerStyle>
</GroupStyle>
</ListView.GroupStyle>
<ListView.ItemTemplate>
<DataTemplate>
<WrapPanel>
<TextBlock FontSize="20" Text="{Binding Name}" Margin="0,0,10,0" VerticalAlignment="Center"/>
<TextBox FontSize="20" BorderBrush="Black" BorderThickness="0,0,0,1" Background="Transparent" Controls:TextBoxHelper.Watermark="Enter value" Text="{Binding Value, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" Margin="0,0,10,0" VerticalAlignment="Center" HorizontalContentAlignment="Center"/>
<TextBlock FontSize="20" Text="{Binding Unit}" VerticalAlignment="Center"/>
</WrapPanel>
</DataTemplate>
</ListView.ItemTemplate>
<ListView.ItemContainerStyle>
<Style TargetType="{x:Type ListViewItem}">
<Setter Property="ToolTip" Value="{Binding Path=Notes}"/>
<Setter Property="Background" Value="Transparent" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ListViewItem}">
<ContentPresenter />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ListView.ItemContainerStyle>
</ListView>
</StackPanel>
Everything is OK in the binding department. What I'd like is to invoke the CollectionChanged event (or something like that) for machines each time a property inside one of its Machine members changes property internally. In other words: if I change, for example, a Parameter inside Parameters inside one of the Machines of machine, I'd like it to update the calculation on
<TextBlock FontSize="20" Text="{Binding Converter={StaticResource throughputCalculationConverter}, UpdateSourceTrigger=PropertyChanged}"/>
Thanks!

Answer 1

To propagate the PropertyChanged notifications from the items inside the collection, you need the collection class that subscribes to the change notifications of its items. The standard ObservableCollection<T> class doesn't do that. You can extend the ObservableCollection<T> as shown below. You can also find more similar examples on SO (e.g. ObservableCollection that also monitors changes on the elements in collection).
[NotifyPropertyChanged]
public class ObservableCollectionEx<T> : ObservableCollection<T>
{
protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
{
if (e.Action == NotifyCollectionChangedAction.Remove)
{
foreach (T item in e.OldItems)
{
((INotifyPropertyChanged) item).PropertyChanged -= OnItemPropertyChanged;
}
}
else if (e.Action == NotifyCollectionChangedAction.Add)
{
foreach (T item in e.NewItems)
{
((INotifyPropertyChanged) item).PropertyChanged += OnItemPropertyChanged;
}
}
base.OnCollectionChanged(e);
}
protected void OnPropertyChanged(string propertyName)
{
base.OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
protected void OnItemPropertyChanged(object sender, PropertyChangedEventArgs e)
{
NotifyPropertyChangedServices.SignalPropertyChanged(this, "Item[]");
NotifyCollectionChangedEventArgs collectionChangedEventArgs = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset);
base.OnCollectionChanged(collectionChangedEventArgs);
}
}
When you use this custom collection class, the collection will raise an event when a property of an item changes. Now you can also tell PostSharp to propagate this notification as a change of the collection property itself using [AggregateAllChanges] attribute applied to the collection property (e.g. Parameters, machines).
[AggregateAllChanges]
public ObservableCollectionEx<Parameter> Parameters { get; set; }
[AggregateAllChanges]
public ObservableCollectionEx<Machine> machines { get; set; }