Databind between one textbox and an ObservableCollection of child objects - wpf

Question

I've the following situation:
class A { myCollection = new ObservableCollection<B>();
....
myCollection.Add(new B1());
myCollection.Add(new B2());
....
for each (B b in myCollection)
b.DoWork();
}
where B is an abstract class with a set of specialized subclasses (let's say B1, B2...).
B has the "State" property, and the DoWork method that is overridden by his subclasses.
The state property is changed differently in each specialized DoWork.
abstract class B {
string _state = null;
public string State
{
get
{
return _state;
}
set
{
_state = value;
OnPropertyChanged( "State" );
}
public bool DoWork();
}
class B1:B {
override public bool DoWork()
{
State = "Press button XXXX to do something";
.....
return true;
}
}
class B2:B {
override public bool DoWork()
{
State = "Press button YYYY to do something else";
....
return true;
}
}
In my xaml file datacontext is A, and I dont't know how to set Binding:
<Window.DataContext>
<!-- Declaratively create an instance of A-->
<VW:A />
</Window.DataContext>
....
<TextBox Text="{Binding Path=????State????}" />
I want to change the TextBox text with databinding when calling
for each (B b in myCollection)
b.DoWork();
I've tryed several binding istructions but it doesn't works....
SOLUTION THANKS TO SHERIGAN:
The SHERIGAN solution is good if you wanto to show all property of all object in the collection togheter, BUT
What i was actually trying to achive was to have a collection of object that all updates the same visual component. Objects in collection represents states, so there is always only one active.
so what i did is edit class A:
class A { myCollection = new ObservableCollection<B>();
....
private B temp;
myCollection.Add(new B1());
myCollection.Add(new B2());
....
for each (B b in myCollection) {
temp = b
temp.DoWork();
}
public B TEMP
{
get
{
return temp;
}
set
{
temp = value;
OnPropertyChanged( "TEMP" );
}
}
and in xaml
<TextBox Text="{Binding Path=TEMP.State}"/>
}

Answer 1

Basically, you'll need a public collection property in class A and it will also need to implement the INotifyPropertyChanged interface. Then you'd need to Bind that collection property to a collection control:
<ListBox ItemsSource="{Binding CollectionProperty}">
...
</ListBox>
Then you can set what each item should look like in the ItemTemplate:
<ListBox ItemsSource="{Binding CollectionProperty}">
<ListBox.ItemTemplate>
<DataTemplate DataType="{x:Type YourXmlNamespace:B}">
<TextBox Text="{Binding Path=State}" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
I have a feeling that using base classes in your XAML will not work, but I could be wrong. You might have to set the DataType property to either B1 or B2 instead. This may or may not work for an instance of A... I can't test this at the moment.
UPDATE >>>
It sounds like you have an empty item in your collection that is having an ItemTemplate (the TextBox) generated for it. However, you don't actually have to use a collection control to display an item from a collection... if you just want to display one item, you should be able to use the indexer Binding.Path syntax:
<TextBox Text="{Binding CollectionProperty[0].State}" />