ValidatorCalloutExtender does not work in Panel if its Visible property is set to false at startup about ajaxcontroltoolkit HOT 3 CLOSED

I realize that problem is not due to initial visibility of controls but more globally to UpdatePanel refresh.
If a callback causes an UpdatePanel.Update() all ValidatorCalloutExtenders inside no longer works, regardless of they were visible or not.

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Would you please provide a sample project with the described markup so that I can research it?

from ajaxcontroltoolkit.

This issue happens when unobtrusive validation is enabled and jQuery is present.

ValidatorCallout is placed inside the UpdatePanel, so it is recreated after the panel's update.
However, ValidatorCallout attaches to the existing validator before unobtrusive validation code reevaluates page validators using component's data-val-evaluationfunction attribute, thus reverting the validation function to the default value.

To fix it, we remove the data-val-evaluationfunction attribute from the validator to which ValidatorCallout is attached (see PR #37).
The validator attachment is placed in the Sys.Application.load event handler to ensure it is executed regardless of the page update mode.

To temporarily workaround this issue in v16.1.0, call the ValidatorCallout's _checkPageValidators() method manually:

<ajaxToolkit:ValidatorCalloutExtender
    BehaviorID="ValidatorCalloutBehavior"
    runat="server" />

<script type="text/javascript">
    var firstLoad = true;

    Sys.Application.add_load(function() {

        if(firstLoad)
        {
            firstLoad = false;
            return;
        }

        var behavior = $find("ValidatorCalloutBehavior");
        var element = behavior.get_element();
        element.removeAttribute("data-val-evaluationfunction");
        behavior._checkPageValidators(behavior, element);
    });
</script>

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