I will start from down down to up the last piece of code has number 1:
1. piece is located should be located in WPGTemplates.xaml (Themes/THEME/WPGTemplates.xaml)
This piece causes that default template (textbox) starts normal wpf validation. Before that there was only ExceptionValidateRule or nothing. I wanted to use DataErrorValidationRule.
2. You should add this to other editors templates if you want to use them. again in WPGTemplates.xaml or in custom templates. It is standard in WPF.
3. I wanted to create form, that you can't close until your property grid is valid. So if you want to do something like that, just add this code to the propertyGrid.cs and bind for example enabled property of "ok" button to IsValid property.
4. This is implementation of IDataErrorInfo interface on "Property" class. It causes validation only if yours instance object implements IDataErrorInfo.
So Example: Just add this code to the concreate files (WPGTemplates.xaml, PropertyViewModel, PropertyGrid. And try to show any object which implements IDataErrorInfo interface. If you have any validation error there yours textxtboxes appears "red" bordered.
Actualy i stopped using WPG. I don't want to write to this forum the reasons. if you want to know my reasons, and solution write me an email: