how to intercept WPF binding for custom processing

Say you have a window with 20 textboxes on it which are all bound to different BLL classes. How do I intercept a value being passed from a textbox to a property when binding with wpf? I'm looking for a generic solution instead of doing this for ever开发者_StackOverflowy property.

I can inherit from the Binding class, but is there an event in that class I can listen to whenever data is passed from an uielement to a property? Or is there a better solution?

The Binding has a Converter property to which you can assign a class that implements IValueConverter. If you can inherit from binding, maybe you can set the Converter in that specialization and go on with that.

I think the solution youn are looking for is a value converter. This msdn page describes how to do this -> http://msdn.microsoft.com/en-us/library/ms752347.aspx#data_conversion.

I may be mistaking but have you tried with converter? Here's a pretty good site you can check it out:

http://www.switchonthecode.com/tutorials/wpf-tutorial-binding-converters

I would like to vote on all three answers but I don't have the reputation for it. Vote for this and i'll vote for you ;)

I solved my problem thanks to you guys!

Here's what I did:

1. Create a new ValueConverter with an event SourceUpdated that fires whenever a value is passed trough it.
2. Inherit all our existing converters from it.

3. Create a new Binding class (which inherits from Binding), in the constructor see if there's a Converter already, if there isn't create one:

   if (Converter == null) {
       Converter = new GcBindingConverter();
   }
   
   if (Converter.GetType().IsAssignableFrom(typeof(GcBindingConverter))) {
       ((GcBindingConverter)Converter).SourceUpdated += SourceUpdatedHandler;
   }
   

4. On each form that needs this functionality wire the events to an event handler, I've put the handler in our modelstate:

   static void WireDirtyBindings(DependencyObject element, ModelStateBase ModelState)
   {
       Binding bb = null;
       // find bindings on elements:
       if ((object.ReferenceEquals(element.GetType, typeof(TextBox)))) {
           bb = BindingOperations.GetBinding(element, TextBox.TextProperty);
       } else if ((object.ReferenceEquals(element.GetType, typeof(ComboBox)))) {
           bb = BindingOperations.GetBinding(element, ComboBox.SelectedValueProperty);
           // other objects...
       }
   
   
   if (bb != null) {
       // wire eventhandler to event:
       doWireHandler(bb, ModelState);
   }
   
   // Now, recurse through any child elements
   if (element is FrameworkElement || element is FrameworkContentElement) {
       foreach (object childElement in LogicalTreeHelper.GetChildren(element)) {
           if (childElement is DependencyObject) {
               WireDirtyBindings((DependencyObject)childElement, ModelState);
           }
       }
   }
   

   }

The only thing I have to write now for each form that has lots of data input is:

BaseBinding.WireDirtyBindings(this, _modelState);

5: In the form, bind the save changes button's enabled state to the modelstate property that says if there are any changes. I could also use an interface for this but since we already have something like a modelstate this is a good place to put it.

This works quite nicely with just a few lines of code. Now I don't have to worry about end users making lots of changes without saving it.