IdValidationRule Class

A warning should be shown if the user starts to put data into the ID field and if it is an old port mapping, i. e. it has been there at the time the dialog has been opened. But, the WPF validation mechanism can only handle errors, not warnings, i. e. the input would be discarded that is not wanted. To avoid this the validation rule is disabled as soon as the focus of the ID field is lost, and the validation is triggered by hand to make the input valid. The validation is enabled again when another ID field gets the focus.

public class IdValidationRule : ValidationRule