What's the easiest way to do negation in triggers?

I want to do something like

<DataTrigger Binding="{Binding Someth开发者_C百科ing}" ValueIsNot="{x:Null}">

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I think your best bet is to use a Converter. See this blog post for a sample for converting a result into a boolean.

<DataTrigger
    Binding="{Binding Path=x, Converter={StaticResource IsNotNullConverter}}"
    Value="true">

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If you want to go with triggers, you could write your own or leverage existing ones. If you're doing MVVM, just bind the view to a property on your VM that does the logic for you.