A layout container (e.g. ValidationGrid or ValidationLayout) that validates all the children controls would be unwieldy, and in most cases not technically possible, on Xamarin.Forms due to the wide array of possible children (native components, Skia components, custom components, etc). Those child components would need to have internal support for validation.
Instead, a 'Validation Framework' that exposes behaviors could be used on the individual controls on your custom page layout (aka 'Form'). The example Yana provided is an excellent example of such an approach. An alternative to behaviors would be to use Attached Properties, a very simple example is what I've written in this GitHub Gist
If you would like to have the development team consider building a Validation Framework for UI for Xamarin that could be used for non Telerik controls, please take a moment to submit a Feature Request here: UI for Xamarin Feedback Porta
The item you submit there goes directly into the development team's back end. When they make status changes to the item, you'll be notified immediately. You could also leave a comment in the Feedback Item with a link back to this forum thread so that they have a better description of what you're looking for.
Lance | Tech Support Engineer, Sr.
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