Customising Error Messages with INotifyDataErrorInfo Validation for XAML Applications (UWP, WinUI, Uno)

In my previous post, Adding Validation to a XAML Control Using INotifyDataErrorInfo, I walked through adding validation to a view model using the INotifyDataErrorInfo interface and the Community Toolkit. This post will pick up where that post left off and look at how you can customise the error message that gets displayed.