Sitecore BeginRouteForm posting raw view without layout

 I got an opportunity to work on a custom MVC form to check if user enters the password correct then redirect to other page otherwise show the error, and this was to be done without ajax.

So I created the controller rendering and in the controller created two method as GetPasswordProtectedLogin() and PostPasswordProtectedLogin(Model formData) Which looks like something as following

[HttpGet]
        public ActionResult GetPasswordProtectedLogin()
        {

            if (_botFinder.IsBotOrCrawler)
            {
                return this.View("/Views/.../..../ProtectedLoginForm.cshtml", null);
            }

            var vm = ProtectedLoginFormViewModel();
            
            vm.IsValid = true;

            return this.View("/Views/.../.../ProtectedLoginForm.cshtml", vm);
        }

        [HttpPost]
        public ActionResult PostPasswordProtectedLogin(ProtectedLoginFormViewModel formModel)
        {

            if (_botFinder.IsBotOrCrawler)
            {
                return this.View("/Views/.../.../ProtectedLoginForm.cshtml", null);
            }
            var vm = new ProtectedLoginFormViewModel
            {
                IsValid = true
            };
            vm = ProtectedLoginFormViewModel(formModel);
            string password = Sitecore.Globalization.Translate.Text("password");
            if (password.Equals(formModel.PasswordValue))
            {
                return this.Redirect(vm.FormSettings.SuccessRedirectionUrl.Url);
            }
            vm.IsValid = false;
            ModelState.AddModelError("Invalid Passcode", vm.FormSettings.PasswordErrorMessage);
            return this.View("/Views/.../..../ProtectedLoginForm.cshtml", vm);
        }

        private rotectedLoginFormViewModel ProtectedLoginFormViewModel(ProtectedLoginFormViewModel formModel = null)
        {
            var vm = new ProtectedLoginFormViewModel();
            FormSettings datasourceItem;
            using (new SitecoreContext(Sitecore.Context.Database))
            {
                datasourceItem = GetDataSourceItem<FormSettings>();
            }
            if (datasourceItem == null && Sitecore.Context.Database.Name.Equals(Master))
            {
                datasourceItem = this.GetDatasourceItem_ExperienceEditor<FormSettings>();
            }
            if (datasourceItem == null && formModel != null)
            {
                datasourceItem = _sitecoreContext.GetItem<FormSettings>(formModel.Guid);
            }
            if (datasourceItem != null)
            {
                vm = PasswordProtectedLoginPageViewModelMapper.Map(datasourceItem);
            }
            else
            {
                return null;
            }

            return vm;
        }

And, the view looks like follows:

@using Glass.Mapper.Sc.Web.Mvc
@inherits Glass.Mapper.Sc.Web.Mvc.GlassView<Website.ViewModels.ProtectedLoginFormViewModel>

@if (Model?.FormSettings != null)
{
    var isEditModeCSSClass = "";
    if (IsInEditingMode)
    {
        isEditModeCSSClass = "show-for-editmode";
    }
    using (Html.BeginRouteForm(Sitecore.Mvc.Configuration.MvcSettings.SitecoreRouteName, FormMethod.Post, new { enctype = "multipart/form-data", name = "Default", @class = "protected-login-form" }))
    {
        @Html.AntiForgeryToken()
         @Html.Sitecore().FormHandler("ControllerName", "PostPasswordProtectedLogin")

        <div class="blue-forms">
            <div class="container">
                <div class="row">
                    <div class="col-sm-12">
                        @*if (!Model.IsValid || IsInEditingMode)
                            {
                                <div class="section-headline form-content form-thankyou-content">
                                    @Editable(Model.FormSettings, x => x.PasswordErrorMessage)
                                </div>
                            }*@
                        @Html.ValidationSummary()
                    </div>
                </div>
                <div class="row">
                    <div class="col-sm-6">
                        <div class="login-form">
                            @Html.LabelFor(vm => vm.PasswordValue, Model.FormSettings.PasswordLabel)
                            @Html.PasswordFor(vm => vm.PasswordValue, new { @Value = "", Class = "elementfocus", id="passwd", placeholder= Model.FormSettings.PasswordPlaceholder })
                            @Html.ValidationMessageFor(vm => vm.PasswordValue)
                            @Html.HiddenFor(vm => vm.Guid)
                        </div>
                    </div>
                    <div class="col-sm-12">
                        @using (BeginEditFrame(Model.FormSettings, null, x => x.ButtonText))
                        {
                            <button type="submit" id="protectedLoginButton" disabled class="btn btn-light">@Model.FormSettings.ButtonText</button>
                        }
                    </div>
                </div>
            </div>
        </div>
    }

}

<script>
    $("#passwd").on('keyup', function () {
        let empty = false;

        empty = $(this).val().length == 0;
        if (empty)
            $('#protectedLoginButton').attr('disabled', 'disabled').removeClass("btn-primary").addClass("btn-light");
        else
            $('#protectedLoginButton').attr('disabled', false).removeClass("btn-light").addClass("btn-primary");
    });
</script>

Everything works fine but when I was submitting the form then it was giving me the view only instead of the complete layout.

Then I checked this issue was faced by many of the Sitecore guys but I found the root cause of this was due to formHandler as per the StackExchange answer here. So to simply it I did three steps

1. Removed the formHandler from the view.
2. Renamed my both Get and Post methods to be the same name as follows:
3. Updated the method name in the controller rendering and after that when I posted the form it was working fine.

[HttpGet]
        public ActionResult ProtectedLogin()
        

[HttpPost]
        public ActionResult ProtectedLogin(ProtectedLoginFormViewModel formModel)

My Final view was as it is shown above just removed/commented this line completely

@*@Html.Sitecore().FormHandler("ControllerName", "PostPasswordProtectedLogin")*@