> Basically I hate it when my ViewModel has to implement all these
> interfaces... It feels like back in Java days to me...

> so the idea here is to still use namescopes but leverage the databinding
> capabilities of WPF... so that you can do something like this

> <Grid focusStuff:FocusedBehaviourTake2.FocusElement="{Binding Focus}">

> and in the VM

> Save = new RelayCommand( x => Focus= "Name");

> Basically in the ViewModel you set a property that exposes the element that
> should get focus. The attached behavior (which accepts binding) will get
> triggered when the property changes. THERE IS ONE SIDE EFFECT OF THIS.
> Basically if the viewmodel sets the Focus property to be the same the
> attached behavior will not get triggered again... this might be a show
> stopper for this idea... what do you guys think?

> which approach would you like best?

> Regards
> Marlon
> WPF Blog - http://marlongrech.wordpress.com/
> Microsoft MVP for Client App

> On Mon, Mar 15, 2010 at 8:25 PM, Daniel Vaughan <dbvaug...@gmail.com>wrote:

>> Good thinking Marlon. As Pete said, very innovative.

>> On Mar 15, 7:33 pm, Marlon Grech <marlongr...@gmail.com> wrote:
>> > something like this... but I need to do something else so that its
>> cooler...

>> > The Idea is that rather then setting an attached property to every
>> element
>> > you want to control you just set it once and find that element by using
>> WPF
>> > Namescopes.

>> > Attached is a prototype... yet I just built this now... did not test
>> it...
>> > and probably I have bugs all over the place.,... I just did it to show
>> you
>> > what I mean

>> > Regards
>> > Marlon
>> > WPF Blog -http://marlongrech.wordpress.com/
>> > Microsoft MVP for Client App

>> > On Mon, Mar 15, 2010 at 5:50 PM, Josh Smith <flappleja...@gmail.com>
>> wrote:
>> > > What do you have in mind?

>> > > On Mon, Mar 15, 2010 at 10:46 AM, Marlon Grech <marlongr...@gmail.com
>> >wrote:

>> > >> mmm... interesting approach... what about leveraging Namescopes for
>> such a
>> > >> thing?

>> > >> Regards
>> > >> Marlon
>> > >> WPF Blog -http://marlongrech.wordpress.com/
>> > >> Microsoft MVP for Client App

>> > >> On Mon, Mar 15, 2010 at 3:12 PM, Peter O'Hanlon <
>> pete.ohan...@gmail.com>wrote:

>> > >>> Sounds good. As far as the FocusScopes go, there shouldn't be any
>> issues,
>> > >>> but it's an edge case to consider (I've been bitten too many times
>> by custom
>> > >>> FocusScopes).

>> > >>> On Mon, Mar 15, 2010 at 3:08 PM, Josh Smith <flappleja...@gmail.com
>> >wrote:

>> > >>>> Thanks Pete. I was thinking that there could be an attached
>> property of
>> > >>>> type bool that is set on an element, instead of setting
>> ValidatedProperty.
>> > >>>>  When set, that attached property figures out which property on the
>> element
>> > >>>> to monitor, such as Text on a TextBox.  This would make it easier
>> than
>> > >>>> having to specify the property, though that would still be an
>> option if you
>> > >>>> need to specify it.

>> > >>>> I'll have to look into FocusScopes, though I don't see any issues
>> there
>> > >>>> (I might be overlooking something...).

>> > >>>> Josh

>> > >>>> On Mon, Mar 15, 2010 at 6:31 AM, Peter O'Hanlon <
>> pete.ohan...@gmail.com
>> > >>>> > wrote:

>> > >>>>> The only thing that stands out to me is that this is going to have
>> to
>> > >>>>> be applied in a lot of places in a typical LOB application, so
>> that might be
>> > >>>>> a little bit tedious. What effects do FocusScope's have here? I'll
>> need to
>> > >>>>> play around with this a bit just to make sure there aren't any
>> edge cases
>> > >>>>> that occur (I'm primarily thinking of cases where loss of focus to
>> a
>> > >>>>> menu/toolbar triggers the validation but the parent FocusScope has
>> changed
>> > >>>>> from the textbox).

>> > >>>>> Pete

>> > >>>>>   On Mon, Mar 15, 2010 at 2:24 PM, Josh Smith <
>> flappleja...@gmail.com>wrote:

>> > >>>>>> Thanks.  Any pitfalls or gotchas sticking their heads out?

>> > >>>>>> On Mon, Mar 15, 2010 at 1:03 AM, Peter O'Hanlon <
>> > >>>>>> pete.ohan...@gmail.com> wrote:

>> > >>>>>>> I like it - I know that it feels "dirty", but it's actually
>> pretty
>> > >>>>>>> darn cool.

>> > >>>>>>>  On Mon, Mar 15, 2010 at 3:54 AM, Josh Smith <
>> flappleja...@gmail.com
>> > >>>>>>> > wrote:

>> > >>>>>>>> A while back Dr. WPF graced us with his clever hack of
>> controlling
>> > >>>>>>>> input focus from VM objects.  It involved hijacking the VM's
>> IDataErrorInfo
>> > >>>>>>>> implementation, and doing all sorts of evil-genius stuff to
>> make the input
>> > >>>>>>>> caret move to the correct element.  Today while I was *trying*
>> to
>> > >>>>>>>> read a great novel, I couldn't stop thinking about another way
>> to control
>> > >>>>>>>> input focus from a viewmodel object.

>> > >>>>>>>> I put the novel down and did a quick spike of the idea.  The
>> source
>> > >>>>>>>> code is attached (rename it from .DOC to .ZIP since gmail is
>> terrified of
>> > >>>>>>>> ZIP files for some reason).  Here's the general idea...

>> > >>>>>>>> Implement this interface on your VM class:

>> > >>>>>>>>  /// <summary>
>> > >>>>>>>> /// Implemented by a ViewModel that needs to control
>> > >>>>>>>> /// where input focus is in a View.
>> > >>>>>>>> /// </summary>
>> > >>>>>>>> public interface IFocusController
>> > >>>>>>>> {
>> > >>>>>>>>     /// <summary>
>> > >>>>>>>>     /// Raised when the input focus should move to
>> > >>>>>>>>     /// a control whose 'active' dependency property
>> > >>>>>>>>     /// is bound to the specified property.
>> > >>>>>>>>     /// </summary>
>> > >>>>>>>>     event EventHandler<MoveFocusEventArgs> MoveFocus;
>> > >>>>>>>> }

>> > >>>>>>>> Next, in your VM object (which might implement IDataErrorInfo),
>> do
>> > >>>>>>>> something like this to support a Save button:

>> > >>>>>>>>  public ICommand SaveCommand
>> > >>>>>>>> {
>> > >>>>>>>>     get { return new RelayCommand(this.Save); }
>> > >>>>>>>> }

>> > >>>>>>>> void Save()
>> > >>>>>>>> {
>> > >>>>>>>>     if (this.HasError)
>> > >>>>>>>>     {
>> > >>>>>>>>         // The Error property knows which property is invalid.
>> > >>>>>>>>         this.RaiseMoveFocus(this.Error);
>> > >>>>>>>>     }
>> > >>>>>>>>     else
>> > >>>>>>>>     {
>> > >>>>>>>>         // Save to database...
>> > >>>>>>>>         System.Windows.MessageBox.Show("Saved");
>> > >>>>>>>>     }
>> > >>>>>>>> }

>> > >>>>>>>> bool HasError
>> > >>>>>>>> {
>> > >>>>>>>>     get { return _validatedProperties.Any(prop =>
>> > >>>>>>>> !String.IsNullOrEmpty(this[prop])); }
>> > >>>>>>>> }

>> > >>>>>>>>  public event EventHandler<MoveFocusEventArgs> MoveFocus;

>> > >>>>>>>> void RaiseMoveFocus(string focusedProperty)
>> > >>>>>>>> {
>> > >>>>>>>>     var handler = this.MoveFocus;
>> > >>>>>>>>     if (handler != null)
>> > >>>>>>>>     {
>> > >>>>>>>>         handler(this, new MoveFocusEventArgs(focusedProperty));
>> > >>>>>>>>     }
>> > >>>>>>>> }

>> > >>>>>>>> Lastly, in your View, use my terribly(?) named attached
>> property to
>> > >>>>>>>> specify which DP on your elements is bound to the validated
>> property of the
>> > >>>>>>>> VM, for example:

>> > >>>>>>>>  <TextBox
>> > >>>>>>>>     Text="{Binding Path=FirstName, ValidatesOnDataErrors=True}"
>> > >>>>>>>>     *local:FocusControl.ValidatedProperty="TextBox.Text"*
>> > >>>>>>>>     />

>> > >>>>>>>> I'm not sure that I like this approach yet.  It's a pretty
>> important
>> > >>>>>>>> topic, so I thought I'd share this out amongst the Disciples
>> for feedback.

>> > >>>>>>>> Thanks,
>> > >>>>>>>> Josh

>> > >>>>>>> --
>> > >>>>>>> Peter O'Hanlon

>> > >>>>> --
>> > >>>>> Peter O'Hanlon

>> > >>> --
>> > >>> Peter O'Hanlon

>> >  TestFocus.zip.doc
>> > 140KViewDownload