Suggested way of validating input controls

4 posts, 0 answers
  1. Carl
    Carl avatar
    17 posts
    Member since:
    Sep 2018

    Posted 12 Oct 2018 Link to this post

    I can't find any documentation related to validating "forms" created using UI for Xamarin controls, I understand that could be something related to xamarin.forms itself but before trying any other options I would like to hear directly from Telerik staff what's is the best suited approach to validate your controls.

    For instance, I'm implementing a login screen using two RadEntry (user and password) and one RadButton, I would like to apply some basic rules to the RadEntries, like they can't be empty then once pressed the button it should trigger those rules and invalidate the form so the user can't submit it until the RadEntries have valid data.

    What is your recommendation of handling this scenario? a behavior? a third party library? attaching by hand the required event for each control?

    P.D.: Are you planning to implement some kind of Form container control where you can trigger a validation event to all controls inside it just like the DataForm control works?

  2. Yana
    Admin
    Yana avatar
    4865 posts

    Posted 15 Oct 2018 Link to this post

    Hi Carl,

    Thank you for your interest in Telerik UI for Xamarin.

    For RadEntry control validation I would recommend using behaviors in a similar way as described here: Behaviors in Xamarin.Forms. Additionally, how the validation results are handled depends mainly on the app requirements.

    RadDataForm control also provides means for validating the entered input through a few validation modes - immediate, on lostfocus and manual (which can be set on button press).  You could learn more about this in our documentation here: DataForm: Validate and Commit
    Having this in mind, I am not sure what you mean with Form container control as currently I believe RadDataForm covers this functionality. Could you elaborate more on this?

    Regards,
    Yana
    Progress Telerik
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  3. Carl
    Carl avatar
    17 posts
    Member since:
    Sep 2018

    Posted 15 Oct 2018 in reply to Yana Link to this post

    @Yana What I meant with a Form container is basically a control that helps to handle validation over more complex customization scenarios, for example at this time I can't use the DataForm control to create cascading dropdowns (is possible but with a high performance cost) or to set specific properties for each control that is rendered by DataForm (like setting specific datasources, or setting specific styles, using custom fonts, etc), there are many limitations right now in the DataForm control, so it would help a lot that I can create by hand my own "form" inside a form container and to set validations over those items
  4. Lance | Technical Support Engineer, Principal
    Admin
    Lance | Technical Support Engineer, Principal avatar
    1002 posts

    Posted 15 Oct 2018 Link to this post

    Hi Carl,

    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.

    Feature Request

    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 Portal.

    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.

    Regards,
    Lance | Tech Support Engineer, Sr.
    Progress Telerik
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