Form with MultiSelect editor does not submit selected values in the MultiSelect.

The Kendo Form should include native ListBox editor support including joining and swapping items between two ListBox's using ConnectWith.

To use a ListBox in the Kendo Form currently requires a custom editor which is overly complex.

Bug report

When a Telerik UI for ASP.NET Core MultiSelect is used in a Form, a JS error is thrown:

jquery.min.js:2 Uncaught Error: Syntax error, unrecognized expression: #
    at Function.se.error (jquery.min.js:2)
    at se.tokenize (jquery.min.js:2)
    at se.select (jquery.min.js:2)
    at Function.se [as find] (jquery.min.js:2)
    at S.fn.init.find (jquery.min.js:2)
    at new S.fn.init (jquery.min.js:2)
    at S (jquery.min.js:2)
    at Object.data ((index):24)
    at init.setup (kendo.all.js:6596)
    at init.read (kendo.all.js:6574)

The issue occurs when using jQuery 3.6.0, but is absent with jQuery v 1.12.4

Reproduction of the problem

@(Html.Kendo().Form<FormViewModel>()
        .Name("exampleForm")
        .HtmlAttributes(new { action = "Items", method = "POST" })
        .Validatable(v =>
        {
            v.ValidateOnBlur(true);
            v.ValidationSummary(vs => vs.Enable(true));
        })
        .Items(items =>
        {
               items.Add()
                        .Field(f => f.MultiSelect)
                        .Label(l => l.Text("MultiSelect:"))
                        .Editor(e =>
                        {
                            e.MultiSelect()
                                .HtmlAttributes(new { })
                                .Placeholder("Select...")
                                .DataTextField("ProductName")
                                .DataValueField("ProductID")
                                .HtmlAttributes(new { style = "width:100%" })
                                .Height(520)
                                .DataSource(source =>
                                {
                                    source.Read(read =>
                                    {
                                        read.Action("Items_GetProducts", "Form");
                                    })
                                    .ServerFiltering(true);
                                });
                        });
             })
    )

    public class FormViewModel
    {
        public List<ProductViewModel> MultiSelect { get; set; }
    }

Runnable sample available in ticket 1540812

Expected/desired behavior

JavaScript error should not be thrown.

Environment

• Kendo UI version: 2021.3.914
• jQuery version: 3.6.0
• Browser: [all]

Bug report

The Form TagHelper does not provide support for hidden fields, similar to the HtmlHelper.

Reproduction of the problem

The Form TagHelper does not allow similar built-in configuration:

.Items(i =>
            {
            i.Add()
                .Field(f => f.UserID)
                .Editor(editor => editor.Hidden());
            })

Expected/desired behavior

The Form TagHelper should support hidden inputs.

Workaround

Similar result can be achieved by setting the editor-handler attribute, creating a hidden input and setting an empty label:

<form-items>
    <form-item field="UserID" editor-handler="hiddenEditor" >
        <item-label text=" " />
    </form-item>
</form-items>

<script>
    function hiddenEditor(container, options) {
        $('<input type="hidden" data-bind="value: ' + options.field + '" name="' + options.field + '"/>')
            .appendTo(container);
    }
</script>

Environment

• Kendo UI version: 2022.3.913
• Browser: [all]

Bug report

Form TagHelper does not expose a ValidationSummary tag.

Current behavior

The Form TagHelper's exposes only a validation-summary attribute instead of a validation-summary tag which prevents adding options such as: Container, Enable, Template, and more.

In comparison to the HTML Helper .ValidationSummary() API configuration which allows the following:

        .Validatable(v =>
        {
            v.ValidationSummary(validationSummary => {
                validationSummary.Enable(true);
                validationSummary.TemplateId("someTemplate");
                validationSummary.Container("myContainer");
            });
        })

Expected/desired behavior

It would be a good idea to consider altering the current validation-summary attribute into a standalone tag helper. However, this will inevitably lead to a breaking change.

Environment

• Kendo UI version: 2023.2.829
• jQuery version: x.y
• Browser: [all]

The FormItemBuilder exposes an EditorTemplateView method which allows a view to represent the item and provides the entire modal to the view.

As the elements available to forms are limited to those hard coded by Telerik and whilst extension methods can be employed to expand this limitation slightly, the ability to create a context specific view would be ideal

The current implementation looks like this

Html.Kendo().Form<Model>()
    .Items(items =>
    {
        items.AddGroup("Test", 1, 10)
            .Items(i =>
                {
                    i.Add().Field(x => x.Username)
                    i.Add().Field(x => x.Password).EditorTemplateView(Html.Partial("MyView"))
                }
            );
    })

In this example, the entire model is provided into MyView. 

I suggest adding an EditorTemplateFor that uses the lamda expression provided in the Field() method such as

Html.Kendo().Form<Model>()
    .Items(items =>
    {
        items.AddGroup("Test", 1, 10)
            .Items(i =>
                {
                    i.Add().Field(x => x.Username)
                    i.Add().Field(x => x.Password).EditorTemplateViewFor(Html.Partial("MyView"))
                }
            );
    })

### Bug report

When loading an editor through a partial View using EditorTemplateView(await Html.PartialAsync("PartialViewName")), the following error occurs:

The 'await' operator can only be used within an async lambda expression. Consider marking this lambda expression with the 'async' modifier.

### Reproduction of the problem

@(Html.Kendo().Form<UserViewModel>()
     .Name("myForm")
     .Items(items =>
     {
         items.Add().Field(f => f.Username).EditorTemplateView(await Html.PartialAsync("PartialViewName"));
      })
)

### Expected/desired behavior

The EditorTemplateView() must accept Html.PartialAsync("PartialViewName").

### Environment

* **Telerik UI for ASP.NET Core version: 2024.4.1112
* **Browser: [all]