WPF: Validation of multiple textboxes

Question

Here's the situation:

I've got 3 textboxes where one put First Name, Last Name and Age respectively. Label with big red "!" shall be only visible when:

Any of the textboxes has no content OR Age (third textbox) is a negative number OR Age is bigger than int.MaxValue.

I already got two validation rules (one for first/last name and another for age). What do I do now? Do I need some kind of converter that checks all three input fields and returns true/false? How to implement this in XAML?

Answer 1

You can use IDataErrorInfo to validate the fields - see this article which explains how to use it. You'll just need to adapt it to have one field displaying errors instead of individual ones for all three.