WPF: Does static Resource with Binding as "TwoWay' supports two way binding?

Question

 <TextBox Name="CustomerName" Height="30" Margin="5"
  Text="{Binding Source={StaticResource MyCustomerData},
   Path=CustomerName, Mode=TwoWay}" Grid.Row="0" Grid.Column="1" />

Above is my xaml snippet

MuCustomerData is my class which implements INotifyPropertyChanged interface and it has a property CustomerName which shall notify about the changes using PropertyChanged event to the View (UI)

Here I bind my class(MyCustomerData) as StaticResource and binding mode as TwoWay. Will this actually work two way? or I should use my class as Dynamic Resource to make the binding work two way? Since only once a StaticResource would get loaded and any further changes will not be taken when it is staticresource .... your thoughts?? I just read this http://www.codeproject.com/Articles/393086/WPF-StaticResource-vs-DynamicResource ..Pls do take a look on this article ..

Of course when you make the mode of binding as Two way it works as two way , what made you think it may not work ? — srsyogesh
@srsyogesh well I think when the resource is a dynamicresource and mode is two way then the binding works two way whereas if the resource is a staticResource and binding is two way it does not.. I aint sure though ..thats y posted the ques! — Arvind897
Try to make your Question title a little shorter and put the actual question in the content portion. Also, I am not seeing the XAML code you supposedly posted. Please revise. — Scott Solmer

Rachel Rachel · Accepted Answer · 2013-11-04T19:38:55

StaticResource and DynamicResource refer to WPF's Resources, not Bindings.

StaticResource evaluates once (usually when the XAML is parsed), and is never evaluated again because WPF assumes the resource is static and won't ever change.

DynamicResource means the resource is dynamic, so evaluate it whenever the value is needed.

In your case, the Source property of your binding will be evaluated once, and never again since it is set to a StaticResource. If you change the MyCustomerData object to a new object, the binding won't evaluate itself again to reflect the change.

But the actual property, CustomerName, will get updated as needed because it is bound using a TwoWay binding.

To look at it another way, you're creating a binding that says something like

var b = new Binding();
b.Source = MyCustomerData;
b.Path = "Name";
b.Mode = TwoWay;

When you set b.Source using a StaticResource, then think of the binding evaluating using b.Source.Name. But if you were to use a DynamicResource, think of it as evaluating with MyCustomerData.Name, and so it would use the current version of MyCustomerData.

So you could set MyCustomerData = new MyCustomerData();` after the binding has been evaluated once, and a dynamic resource would evaluate that correctly, while a static resource would not.

WPF: Does static Resource with Binding as "TwoWay' supports two way binding?

2 Answers