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Child Collection Conundrum
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Threading;
namespace SilverlightApplication12
{
public partial class MainPage : UserControl
{
public MainPage()
{
InitializeComponent();
SynchronizationContext _synchronizationContext = SynchronizationContext.Current;
IMyFactory controller = new MyFactory();
controller.CreateNewMyParent(parent =>
_synchronizationContext.Post(state =>
{
parent.ParentName = "Parent 1";
Timer t = new Timer(s =>
_synchronizationContext.Post(state2 =>
{
controller.CreateNewMyChild(child =>
this.Dispatcher.BeginInvoke((Action)(() =>
{
child.ChildName = "IMyChild Timer";
parent.MyChildCollection.Add(child);
})));
}, null),
null, 1000, 1000);
controller.CreateNewMyChild(child =>
_synchronizationContext.Post(state2 =>
{
child.ChildName = "Child 1 A";
parent.MyChildCollection.Add(child);
}, null));
controller.CreateNewMyChild(child =>
_synchronizationContext.Post(state2 =>
{
child.ChildName = "Child 1 B";
parent.MyChildCollection.Add(child);
}, null));
controller.CreateNewMyChild(child =>
_synchronizationContext.Post(state2 =>
{
child.ChildName = "Child 1 C";
parent.MyChildCollection.Add(child);
}, null));
this.DataContext = parent;
}, null));
}
}
}
using System;
using System.Linq;
using System.Collections.ObjectModel;
using System.Collections.Generic;
using System.ComponentModel;
using System.Collections;
using System.Collections.Specialized;
using System.Threading;
using System.Windows.Threading;
namespace SilverlightApplication12
{
public class MyParent : IMyParent
{
private readonly SynchronizationContext _synchronizationContext;
public MyParent()
{
_myChildBOCollection = new ObservableCollection<MyChild>();
_myChildCollection = new ChildBinder<IMyChild, MyChild>(_myChildBOCollection);
_synchronizationContext = SynchronizationContext.Current;
Timer t = new Timer(s =>
_synchronizationContext.Post(state =>
{
MyChild child = new MyChild();
child.ChildName = "MyChild Timer";
this.MyChildBOCollection.Add(child);
}, null),
null, 777, 777);
}
public string ParentName
{
get { return _parentName; }
set
{
if (_parentName != value)
{
_parentName = value;
OnPropertyChanged("ParentName");
}
}
}
private string _parentName;
public ObservableCollection<MyChild> MyChildBOCollection
{
get { return _myChildBOCollection; }
}
private ObservableCollection<MyChild> _myChildBOCollection;
public ObservableCollection<IMyChild> MyChildCollection
{
get { return _myChildCollection; }
}
private ObservableCollection<IMyChild> _myChildCollection;
private void OnPropertyChanged(string p)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(p));
}
public event PropertyChangedEventHandler PropertyChanged;
}
public class MyChild : IMyChild
{
public string ChildName
{
get { return _childName; }
set
{
if (_childName != value)
{
_childName = value;
OnPropertyChanged("ChildName");
}
}
}
private string _childName;
private void OnPropertyChanged(string p)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(p));
}
public event PropertyChangedEventHandler PropertyChanged;
}
public class MyFactory : IMyFactory
{
public MyFactory() { }
public void CreateNewMyParent(Action<IMyParent> callback)
{
callback(new MyParent());
}
public void CreateNewMyChild(Action<IMyChild> callback)
{
callback(new MyChild());
}
}
public interface IMyParent : INotifyPropertyChanged
{
string ParentName { get; set; }
ObservableCollection<IMyChild> MyChildCollection { get; }
}
public interface IMyChild : INotifyPropertyChanged
{
string ChildName { get; set; }
}
public interface IMyFactory
{
void CreateNewMyParent(Action<IMyParent> callback);
void CreateNewMyChild(Action<IMyChild> callback);
}
public class ChildBinder<IT, T> : ObservableCollection<IT>
where T : IT
{
private readonly ObservableCollection<T> _bindTo;
public ChildBinder(ObservableCollection<T> bindTo)
{
_bindTo = bindTo;
_bindTo.CollectionChanged += new NotifyCollectionChangedEventHandler(_bindTo_CollectionChanged);
this.CollectionChanged += new NotifyCollectionChangedEventHandler(ChildBinder_CollectionChanged);
}
void ChildBinder_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
switch (e.Action)
{
case NotifyCollectionChangedAction.Add:
foreach (T t in this.OfType<T>())
if (!_bindTo.Contains(t))
_bindTo.Add(t);
break;
case NotifyCollectionChangedAction.Remove:
foreach (T t in _bindTo.OfType<T>())
if (_bindTo.Contains(t))
_bindTo.Remove(t);
break;
}
}
void _bindTo_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
switch (e.Action)
{
case NotifyCollectionChangedAction.Add:
foreach (T t in _bindTo)
if (!this.Contains(t))
this.Add(t);
break;
case NotifyCollectionChangedAction.Remove:
foreach (T t in _bindTo)
if (this.Contains(t))
this.Remove(t);
break;
}
}
}
}
<UserControl x:Class="SilverlightApplication12.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400">
<Grid x:Name="LayoutRoot" Background="White">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<TextBlock Text="{Binding ParentName}" />
<ScrollViewer Margin="30,10,10,10" Grid.Row="1">
<ItemsControl ItemsSource="{Binding MyChildCollection}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding ChildName}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</ScrollViewer>
</Grid>
</UserControl>
@ghost

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Owner Author

@ghost ghost commented Dec 28, 2011

Here's an attempt to capture the essence of the interface design goals:

I want the app code to know only of the IMyFactory, IMyParent, and IMyChild interfaces, not the concrete underlying classes
I want the app code to create new IMyParent and IMyChild objects using IMyFactory
I want to expose the strongly-typed child collection (of IMyChild objects) through my IMyParent interface. 
I want the app code to be able to add a factory-created IMyChild to the IMyParent-exposed strongly-typed child collection (of IMyChild objects)
I want the app code to be able to bind to the IMyParent-exposed strongly-typed child collection (of IMyChild objects) and pick up collection changed events so the view updates when items are added or removed from the child collection
I want the IMyFactory, IMyParent, and IMyChild have no dependency on CSLA or other framework that creates MyParent and MyChild classes, but I usually these frameworks create ObservableCollection<MyChild> for the child collection
I want the implementation to run in Silverlight & in WPF

So I just hand the app code an IMyFactory and an IMyParent and it goes about its work...

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