asp-validation-summary not showing, field validation working

Also you can include jquery script for validation tag-helper

<form asp-controller="home" asp-action="CreatePoll" method="post" class="mt-3">
        <div class="validation" asp-validation-summary="All"></div>
        <div class="form-group">
            <label asp-for="Name">Name of the Poll:</label>
            <input asp-for="Name" class="form-control" />
            <span asp-validation-for="Name" class="text-danger"></span>
        </div>

            <button type="submit" class="btn btn-primary">Create</button>

    </form>

    @section scripts{

        <script src="~/lib/jquery-validation/dist/jquery.validate.min.js"></script>
        <script src="~/lib/jquery-validation-unobtrusive/jquery.validate.unobtrusive.min.js"></script>
    }

I had the same issue, field validation worked well, can display xx is required below the input window. But the validation-summary didn't show up.

At first, I have code below in my cshtml file,

<div class="row">
    <div asp-validation-summary="ModelOnly"></div>
    @Html.ValidationSummary(false, "", new { @class = "text-danger" })
</div>

and I had code below in my controller,

ModelState.AddModelError("key", "validation summary error");
return View(rdl);

then only @Html.ValidationSummary() worked, and asp-validation-summary didn't show up(if it displayed message, it should have black font)

Then I tried asp-validation-summary="All", it worked. The difference between ALL and ModelOnly is ModelOnly will only display the invalid message for the model.

So I use ModelState.AddModelError("", "validation summary error."); in my Controller to make the <div asp-validation-summary="ModelOnly"></div> display error message.

I only know it can make it display correctly, but I don't know why...

Display field level error messages using ValidationSummary:

By default, ValidationSummary filters out field level error messages. If you want to display field level error messages as a summary then specify excludePropertyErrors = false.

Example: ValidationSummary to display field errors

@Html.ValidationSummary(false, "", new { @class = "text-danger" })

So now, in the view will display error messages as a summary at the top. Please make sure that you don't have a ValidationMessageFor method for each of the fields.

official doc:https://msdn.microsoft.com/en-us/library/system.web.mvc.html.validationextensions.validationsummary(v=vs.118).aspx

Hope it will be helpful

Thanks

Karthik

You should add this for each your model field with asp-validation-summary="ModelOnly" and set @Html.ValidationSummary() before html form

//Validation Summary Parameters
public static MvcHtmlString ValidationSummary(
    this HtmlHelper htmlHelper,
    bool excludePropertyErrors, // to include or exclude your field validation errors
    string message,
    object htmlAttributes,
    string headingTag
)

@Html.ValidationSummary() // use this with your desired parameters
<form>
  ...... // your inputs
  <input asp-for="YourField" class="form-control" />
  <span asp-validation-for="YourField" class="text-danger"></span>
</form>