You can use an IValueConverter for this:
<TextBlock>
<TextBlock.Resources>
<conv:IsNullConverter x:Key="isNullConverter"/>
</TextBlock.Resources>
<TextBlock.Style>
<Style>
<Style.Triggers>
<DataTrigger Binding="{Binding SomeField, Converter={StaticResource isNullConverter}}" Value="False">
<Setter Property="TextBlock.Text" Value="It's NOT NULL Baby!"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
Where IsNullConverter is defined elsewhere (and conv is set to reference its namespace):
public class IsNullConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
return (value == null);
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new InvalidOperationException("IsNullConverter can only be used OneWay.");
}
}
A more general solution would be to implement an IValueConverter that checks for equality with the ConverterParameter, so you can check against anything, and not just null.