MSDN Community: Windows / WinUI / Discussions / 98765

How to handle null references in WinUI ListViews

Posted: 2 days ago Last reply: 5 hours ago Views: 1.2k Replies: 15

Posted by John Doe

Hi everyone,

I'm encountering an issue with my WinUI 3 application, specifically when populating a ListView. I'm binding a collection of objects to the ItemsSource, but occasionally, some of these objects can have null properties. When the ListView tries to display these null properties (e.g., in a TextBlock's Text property), it throws a System.NullReferenceException.

I've tried a few things:

Checking for nulls in my ViewModel before adding to the collection.
Using a converter to return an empty string for null values.

The converter approach works for simple TextBlocks, but I also have more complex scenarios with custom data templates that involve multiple controls. It feels like there should be a more robust, declarative way to handle this directly within the XAML.

Has anyone faced a similar problem? What are the recommended best practices for preventing NullReferenceExceptions in WinUI ListView items, especially within custom data templates?

Here's a simplified example of my DataTemplate:

<DataTemplate x:Key="MyItemTemplate">
    <StackPanel Orientation="Vertical" Spacing="8">
        <TextBlock Text="{Binding PropertyA}" FontWeight="Bold"/>
        <TextBlock Text="{Binding PropertyB}"/>
        <!-- This TextBlock is problematic if PropertyC is null -->
        <TextBlock Text="{Binding PropertyC}" Foreground="Gray"/>
    </StackPanel>
</DataTemplate>

Any advice or code examples would be greatly appreciated!

Replies (15)

Jane Smith • 1 day ago

Hi John,

This is a common challenge. Your converter approach is valid, but for more complex templates, you might consider using a null-coalescing operator directly in your binding.

For example:

<TextBlock Text="{Binding PropertyC, FallbackValue=''}" Foreground="Gray"/>

Or if you want to bind to a specific string when null:

<TextBlock Text="{Binding PropertyC, TargetNullValue='N/A'}" Foreground="Gray"/>

These binding extensions handle the null case gracefully without throwing exceptions.

Peter Jones • 1 day ago

Another approach, especially if you need to conditionally show/hide elements based on null values, is to use a ValueConverter that returns a boolean or an object, and then use that in a {Binding ... RelativeSource={RelativeSource Mode=TemplatedParent}} binding or within a VisualState.

However, for simple text display, FallbackValue or TargetNullValue are usually the cleanest.

John Doe • 23 hours ago

@Jane Smith, @Peter Jones, thanks for the quick responses!

The FallbackValue and TargetNullValue bindings are exactly what I was looking for. I tested `FallbackValue=''` and it worked perfectly for my problematic TextBlock. I'll integrate this into my other templates as well.

I wasn't aware of these built-in binding properties. Much cleaner than manual checks everywhere!

Alice Brown • 18 hours ago

Just to add, if the null is not expected and might indicate a data integrity issue, it's worth ensuring your data layer or ViewModel is properly validating and handling potential nulls before they even reach the UI. But for UI display purposes, the binding extensions are great.

Bob White • 10 hours ago

Confirming that FallbackValue and TargetNullValue are the standard and recommended ways to handle this in WPF and WinUI. No need to overcomplicate it.

Jane Smith • 5 hours ago

Glad it helped, John! Those binding parameters are quite powerful for simplifying UI logic.

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