Dependency Properties: 'Freezing' DataBinding until user commits - wpf

Question

I am trying to implement a system that would enhance WPF's DataBinding engine.
My prime concern right now is the following:
I would like to be able to 'freeze' the DependencyProperty - stop it from updating from the Model - once the user has started to input something in the UI.
Consider the following example:
I am binding a TextBox.TextProperty to some property on my ViewModel.
The user started typing inside the textbox, and the moment he starts to type, I want to prevent the ViewModel from updating the View.
Only after commiting the change, the user will see the update in the model.
I am trying to create some kind of MultiBinding using a a bool-flag which will tell me whether we need to update the GUI or not, but other than that I don't know how to continue.
Any help would be appreciated!

Answer 1

You can do that by setting UpdateSourceTrigger to PropertyChanged in binding and then set the flag accordingly in the setter of bounded property. PropertyChanged value Updates the binding source immediately as user will input any character.
xaml
<TextBox Text="{Binding Name, UpdateSourceTrigger=PropertyChanged}"/>
ViewModel
public class ViewModel:INotifyPropertyChanged
{
bool stopUpdate;
string name;
public string Name
{
get
{ return name;}
set
{
name = value;
stopUpdate=true;
OnPropertyChanged("Name");
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void OnPropertyChanged(string propName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propName));
}