>>>Hi,
>>>Given, say, this binding in XAML:

<TextBox Width="200" Text="{Binding Path=SelectedItem.Text, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"></TextBox>

where 'SelectedItem' may or may not have a 'Text' property.
>>>
>>>It would be ideal to have some method of binding the 'IsEnabled' property so that the control was disabled if the binding fails but I can't think of a way of implementing this in a generic sort of way (I can't even find a way of detecting when the binding fails except by programatically monitoring the Trace - which is kludgy at best and certainly not something to use in production code)
>>>
>>>Any suggestions?
>>>Viv
>>
>>Can't test right now... :-(
>>
>>But... IIRC correctly when the binding fails in the above scenario the Text property will return null? (If not this idea won't work)
>>
>>If it does bind to the text property with a null to Boolean converter and use that to set the IsEnabled property.
>>
>>HTH
>
>Hi,
>Good thought. But if you were referring to the TextBoxText property this is an empty string when the binding fails (which, of course, could equally be a valid value for a successful binding)
>
>I did plug in a value converter - but again that only fires when the binding succeeds.
>But I did get it to work using that plus setting the FallbackValue to false on the binding:

IsEnabled="{Binding Path=Text,Mode=TwoWay, Converter={StaticResource Conv},FallbackValue=False}"

Of course, this way, the ValueConverter can be pretty simple! :

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
>        {
>                return true;
>        }

:-}
>Thanks for starting me in a working direction. I'd still like to come up with a more 'generic' way of doing this though - other 'SelectedItems' might require input from controls other than a TextBox......

The FallbackValue trick was pretty slick, I haven't seen that one before.

I guess my question would be... why is the binding failing? Maybe something you can latch onto there like the type of the selected item?