What are the special values of WPF's Binding engine when converting values?

Question

I already know about the Binding.DoNothing that one can return from an IValueConverter implementation to signify that no other operation should take place.

However, I cannot find a reference, or documentation nicely summing out, what the other special values are - such as returning the fallback value. What are they?

Publias

Fallback happens if the binding does not work in the first place or possibly if some exception is thrown when binding. – Stereogram

the best way to know about such values is to read articles about Binding and BindingBase classes. Everything you can use is listed there – Tim

Answer 1

Binding.DoNothing is an object instance that you actively return from a value converter; it instructs the binding engine to not update the value of the target property at all. Here's a nice example by Josh Smith of what you might use this for.

FallbackValue is a property that you set on bindings; it allows you to specify the value to be applied to the target property if:

• the binding source cannot be resolved (e.g. wrong binding path), or
• the binding property value is equal to DependencyProperty.UnsetValue, or
• a value converter used for the binding throws an exception, or
• a value converter used for the binding returns DependencyProperty.UnsetValue, or
• the value produced by the binding pipeline is not valid for the target property (e.g. wrong type)

TargetNullValue is also a property you set on bindings; it allows you to specify the value to be applied to the target property if the value of the source property is null. For example, if you bind a text box to a string property TargetNullValue lets you pick what appears in the text box if the source string is null.

Sabayon

Ah! DependencyProperty.UnsetValue. That was the one I was looking for. – Publias