I've published a new CodeProject article covering form validation in Calcium. While the form validation APIs are cross-platform, this article is specific to UWP. It could however be applied to WPF, Xamarin Android & iOS.
In this article, you see how to perform both synchronous and asynchronous form validation in a UWP app. You see how set up viewmodel properties for validation, both declaratively and programmatically. You look at how to define your validation logic in a single method or to have the validation logic reside on a remote server. You also see how to use UWP dictionary indexers to bind form validation errors to a control in your view. You then explore the innerworkings of the validation system, and see how Calcium decouples validation from your viewmodel so that it can be used with any object implementing INotifyPropertyChanged.
Read more https://www.codeproject.com/Articles/1166859/UWP-Form-Validation-with-Calcium