Error while creating hidden field for model in ASP.net MVC 5

Question

I m trying to render a hidden field in partial view for model which is an enum

my code is

@model App.PrivacyLevelEnum
@Html.HiddenFor(m=>m);

I have checked Model is not empty but i am getting following error while rendering the view

Value cannot be null or empty.\r\nParameter name: name

Stack trace

   at System.Web.Mvc.Html.InputExtensions.InputHelper(HtmlHelper htmlHelper, InputType inputType, ModelMetadata metadata, String name, Object value, Boolean useViewData, Boolean isChecked, Boolean setId, Boolean isExplicitValue, String format, IDictionary`2 htmlAttributes)
   at System.Web.Mvc.Html.InputExtensions.HiddenHelper(HtmlHelper htmlHelper, ModelMetadata metadata, Object value, Boolean useViewData, String expression, IDictionary`2 htmlAttributes)
   at System.Web.Mvc.Html.InputExtensions.HiddenFor[TModel,TProperty](HtmlHelper`1 htmlHelper, Expression`1 expression, IDictionary`2 htmlAttributes)
   at System.Web.Mvc.Html.InputExtensions.HiddenFor[TModel,TProperty](HtmlHelper`1 htmlHelper, Expression`1 expression)
   at ASP._Page_Views_Profile_PrivacyLevel_cshtml.Execute() in c:\TFS\DEFAULTCOLLECTION\Gac.Hr\Development\Source\Gac.Hr.Web.Html5\Views\Profile\PrivacyLevel.cshtml:line 58
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance)
   at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer)
   at System.Web.Mvc.HtmlHelper.RenderPartialInternal(String partialViewName, ViewDataDictionary viewData, Object model, TextWriter writer, ViewEngineCollection viewEngineCollection)
   at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData)
   at ASP._Page_Views_Profile_ProfileDetailsEditor_cshtml.Execute() in c:\TFS\DEFAULTCOLLECTION\Gac.Hr\Development\Source\Gac.Hr.Web.Html5\Views\Profile\ProfileDetailsEditor.cshtml:line 107
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance)
   at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer)
   at GacHrUI.Controllers.ProfileController.StringifyView(String viewName, Object model) in c:\TFS\DEFAULTCOLLECTION\Gac.Hr\Development\Source\Gac.Hr.Web.Html5\Controllers\ProfileController.cs:line 62
   at GacHrUI.Controllers.ProfileController.RenderEditMode() in c:\TFS\DEFAULTCOLLECTION\Gac.Hr\Development\Source\Gac.Hr.Web.Html5\Controllers\ProfileController.cs:line 35
   at lambda_method(Closure , ControllerBase , Object[] )
   at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
   at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
   at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.ActionInvocation.InvokeSynchronousActionMethod()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.b__39(IAsyncResult asyncResult, ActionInvocation innerInvokeState)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
   at System.Web.Mvc.Async.AsyncResultWrapper.End[TResult](IAsyncResult asyncResult, Object tag)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.b__3d()
   at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.c__DisplayClass46.b__3f()

Quick help will be really appreciated

Answer 1

Your issue here is not an empty model but an incorrect usage of HiddenFor attribute

The signature of a method is :

HiddenFor<TModel, TProperty>(HtmlHelper<TModel>, Expression<Func<TModel, TProperty>>) 

where Expression<Func<TModel, TProperty>> specifies a model property for which you are going to generate a hidden input. This expression looks something like model => model.Name. If I make a long story short, this expression is then used to generate name and id attributes for the generated html input

In your case, the expression that you provide generates an empty name which is invalid. This is the method that throws an exception (from MVC source code):

 private static MvcHtmlString InputHelper(HtmlHelper htmlHelper, InputType inputType, ModelMetadata metadata, string name, object value, bool useViewData, bool isChecked, bool setId, bool isExplicitValue, string format, IDictionary<string, object> htmlAttributes)
        {
            string fullName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name);
            if (String.IsNullOrEmpty(fullName))
            {
                throw new ArgumentException(MvcResources.Common_NullOrEmpty, "name");
            } 
          ... 
         }

Now about possible solutions:

1) Decorate your property in model with [HiddenInput(DisplayValue = false)] (MSDN)- this way you wont have to create a partial view at all. Usage:

2) Create an EditorTemplate. You can call it HiddentEnum.cshtml for example (Make sure to store it under Views/Shared/EditorTemplates folder):

  @model Enum

  @Html.HiddenFor(model=>model)

Usage:

 @Html.EditorFor(model => model.TestEnum, templateName: "HiddenEnum")