Data Trigger where value is not Null - wpf

Question

I want to set some text where the value is not null.
XAML:
<TextBlock >
<TextBlock.Style>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="Text" Value="solved"/>
<Style.Triggers>
<DataTrigger Binding="{Binding Report}" Value="{x:Null}">
<Setter Property="Text" Value=""/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
Note: Here Report is STRING which has some random value like (e.g 11,112,11a)
it shows solved in every row which seems that data trigger is not working.
but its working with this code with this random value (e.g 11,112,11a)
<TextBlock Text="{Binding Report}"/>
I want Solved as text instead of that random values (e.g 11,112,11a) otherwise blank where there is no value.

Answer 1

You could use a converter like so:
xaml:
xmlns:cnv="clr-namespace:Converters"
...
<TextBlock Text="{Binding Report, Converter={cnv:CustomNullToStringConverter NotNullValue=Solved,NullValue=''}}"/>
Converter:
class CustomNullToStringConverter : MarkupExtension, IValueConverter
{
public string NullValue { get; set; }
public string NotNullValue { get; set; }
public override object ProvideValue(IServiceProvider serviceProvider)
{
return this;
}
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (value is string && String.IsNullOrEmpty(value as string)) return NullValue;
if (value == null) return NullValue;
return NotNullValue;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}