How does WPF handle binding to the property of a null object?

Question

I have a listBox using an itemTemplate that contains the following line:

Answer 1

In BindingBase have two properties: TargetNullValue and FallbackValue.

TargetNullValue returns your value when the value of the source is null.

FallbackValue returns your value when the binding is unable to return a value.

Example of using:

<!-- xmlns:sys="clr-namespace:System;assembly=mscorlib" -->

<Window.Resources>
    <!-- Test data -->
    <local:TestDataForImage x:Key="MyTestData" />

    <!-- Image for FallbackValue -->
    <sys:String x:Key="ErrorImage">pack://application:,,,/NotFound.png</sys:String>

    <!-- Image for NULL value -->
    <sys:String x:Key="NullImage">pack://application:,,,/NullImage.png</sys:String>
</Window.Resources>

<Grid DataContext="{StaticResource MyTestData}">
    <Image Name="ImageNull"
           Width="100" 
           Height="100"
           Source="{Binding Path=NullString, TargetNullValue={StaticResource NullImage}}" />

    <Image Name="ImageNotFound"
           Width="100" 
           Height="100" 
           Source="{Binding Path=NotFoundString, FallbackValue={StaticResource ErrorImage}}" />
</Grid>

See this links, for more information:

BindingBase.TargetNullValue Property

BindingBase.FallbackValue Property