https://learn.microsoft.com/en-us/dotnet/api/system.windows.data.bindingbase.shouldserializefallbackvalue?view=windowsdesktop-10.0
BindingBase.ShouldSerializeFallbackValue Method (System.Windows.Data) | Microsoft Learn
Returns a value that indicates whether serialization processes should serialize the effective value of the FallbackValue property on instances of this class.
methodsystemwindowsdatamicrosoft