|value||The value to convert from|
|targetType||The type being converted to|
|parameter||Optional value to control how the conversion works|
|culture||CultureInfo object - required if localisation needed|
Convert method converts the value from the source (usually the view model) to the target (usually a property of a control).
ConvertBack method converts the value from the target back to the source. It is only needed if the binding is
ConvertBack is not supported, i.e. there is no one-to-one mapping between the pre-conversion value and the post-conversion value, it's common practice to have the
ConvertBack method return
DependencyProperty.UnsetValue. It's a better option than throwing an exception (e.g.
NotImplementedException) as it avoids unexpected runtime errors. Also, bindings can benefit of their
DependencyProperty.UnsetValue is returned by a converter.