WPF problems refreshing a textblock

[Klerk]

I am building a small wpf app. When a button gets clicked a third
party dll function constructs a tree like object. This object is bound
to a treeview. This works fine but takes a bit of time to load. As the
dll function constructs the object it prints progress info to the
console. I want to redirect this into a TextBlock so that the user
gets to see the progress messages.

My window ctor looks like this:

InitializeComponent();
StringRedir s = new StringRedir(ref ProgressTextBlock);
Console.SetOut(s);
Console.SetError(s);
this.DataContext = s;

xaml:
<TextBlock Text="{Binding Path=Text}" Width="244"
x:Name="ProgressTextBlock" TextWrapping="Wrap" />
<TreeView >...</TreeView>

The StringRedir class is shown below. The problem is the TextBlock for
some reason does not get updated with the messages until the TreeView
gets loaded. Stepping through I see the Text property being updated
but the TextBlock is not getting refreshed. I added a MessageBox.Show
() at the point where Text gets updated and this seems to cause the
window to refresh each time and I am able to see each message. So I
guess I need some way to explicitly refresh the screen...but this
doesnt make sense I thought the databinding would cause a visual
refresh when the property changed. What am I missing here? How do I
get it to refresh? Any advice is appreciated!


public class StringRedir : StringWriter , INotifyPropertyChanged
{
private string text;
private TextBlock local;

public string Text {
get{ return text;}
set{
text = text + value;
OnPropertyChanged("Text");
}
}

public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(name));
}
}

public StringRedir(ref TextBlock t)
{
local = t;
Text = "";
}

public override void WriteLine(string x)
{
Text = x +"\n";
//MessageBox.Show("hello");
}

}