WPF - INotifyDataErrorInfo

Use case: there's a field or multiple fields that just need some simple adornment saying that the input provided isn't accepted.

The gist: On the base ViewModel class, implement the interface. Errors are tracked per property on a given ViewModel, and there's a dictionary of <string, List<string>> that stores any errors that a given property might run into. The list of errors as strings are then rendered on the associated XAML given a correct XAML implementation.

The simple setup: https://social.technet.microsoft.com/wiki/contents/articles/19490.wpf-4-5-validating-data-in-using-the-inotifydataerrorinfo-interface.aspx

A more complicated/advanced setup that removes the dictionary and has users implement error validation that computes error state on demand: https://stackoverflow.com/a/34722607