The Validation Summary Tag Helper

The validation summary tag helper targets the HTML div element, and is used to render a summary of form validation error messages.

Attribute	Description
validation-summary	A ValidationSummary enumeration that specifies what validation errors to display.

Possible ValidationSummary enumeration values are:

Enum	Description
None	providing no validation summary (the default)
ModelOnly	summarising only model validation errors
All	summarising model and property validation errors

For more information on the various types of error (model or property), see the Validation topic.

Notes

The validation summary tag helper is normally placed at the top of the form. Individual items that form the summary are displayed in an unordered list:

<div class="validation-summary-errors" data-valmsg-summary="true">
    <ul>
        <li>The FirstName field is required.</li>
        <li>The LastName field is required.</li>
        <li>The DateOfBirth field is required.</li>
    </ul>
</div>

You can include additional content to appear before the summary list by adding it to the content of the validation summary tag helper:

<div asp-validation-summary="All">
    <span>Please correct the following errors</span>
</div>

The list of validation error messages is appended to any existing content. The additional content will be visible by default. If you don't want users to see the content unless the page is invalid, change the validation-summary-valid CSS class (which is injected into the div by the tag helper when the page is valid) so that it hides the div or its content:

.validation-summary-valid { display: none; }

or, suitable for the example above where the additional content is in a span:

.validation-summary-valid span { display: none; }

If you specify None as the value for the validation-summary attribute, an empty div is rendered. None results in the tag helper doing nothing.