WPF Binding FallbackValue set to Binding

user_182703 0
Viewed 22536

Is there a way to have another binding as a fallback value?

I'm trying to do something like this:

<Label Content="{Binding SelectedItem.Name, ElementName=groupTreeView,
                         FallbackValue={Binding RootGroup.Name}}" />

If anyone's got another trick to pull it off, that would be great.

fallback data-binding wpf
3 Answers

What you are looking for is something called PriorityBinding (#6 on this list)

(from the article)

The point to PriorityBinding is to name multiple data bindings in order of most desirable to least desirable. This way if the first binding fails, is empty and/or default, another binding can take it's place.

e.g.

<TextBox>
    <TextBox.Text>
        <PriorityBinding>
            <Binding Path="LastNameNonExistant" IsAsync="True" />
            <Binding Path="FirstName" IsAsync="True" />
        </PriorityBinding>
    </TextBox.Text>
</TextBox>
user_1639160

Under what conditions would you like it to use the Fallback value? How would you determine that a binding has failed? A binding is still valid even if it's bound to a null value.

I think a good bet may be to use a converter to convert to a default value if the binding returns null. I'm not sure how you could default to another bound value though.

Check out converters here

user_473390
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