WPF (MVVM) databing issue

Question

hi All,

when I bind a property in the child viewmodel to a textbox, the source won't get updated no matter what mode i set on the binding.

the xaml code is like this:

<TextBox Text="{Binding Path=OrderDetail.CashPaid, Mode=TwoWay}"/>

when the view loaded, the binding system query the CashPaid property once. but whenever the text is edited, the value won't update the source. I must missing something here or the WPF databinding system does not support this kind of binding.

thx

Kevin

Answer 1

By default, TextBox will only update the source of the binding when focus leaves the control. If you set UpdateSourceTrigger to PropertyChanged, the property will be updated as the user types:

<TextBox Text="{Binding Path=OrderDetail.CashPaid, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>

Answer 2

You also need to make sure OrderDetail implements INotifyProperty changed and make sure that your CashPaid property is notified when it changes. See the MSDN doc for more info on this one.

http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx