모델 클래스의 인스턴스가 뷰에 전달되지 않을 때 Create.cshtml의 EditorFor (x = x.Prop)에서 생성 된 null 예외를 방지하는 방법은 무엇입니까?

Question

제약 :

1. 나는 Nullable 유형을 사용하지 않습니다.
2. HttpGet -handling Create 조치 메소드에서 모델 클래스를 인스턴스화하고 싶지 않습니다.

모델 클래스 :

namespace MvcTest.Models 
{ 
    public enum Gender { Male, Female } 
    public class Person 
    { 
     public Gender Gender { get; set; } 
    } 
} 

템플릿 기반 편집기 도우미 (Gender.cshtml)

@using MvcTest.Models 
@model Gender 
@{ 
    var genders = from Gender g in Enum.GetValues(typeof(Gender)) 
        select new { Value = g, Text = g.ToString() }; 

    var sl = new SelectList(genders, "Value", "Text", Model); 
} 
@Html.DropDownList(string.Empty, sl, "--Select--") 

컨트롤러 :

using System.Web.Mvc; 
using MvcTest.Models; 

namespace MvcTest.Controllers 
{ 
    public class HomeController : Controller 
    { 
     public ActionResult Create() 
     { 
      //Person p = new Person(); 
      //return View(p); 

      return View(); 
     } 

    } 
} 

보기 :

@model MvcTest.Models.Person 
@using (Html.BeginForm()) 
{ 

    @Html.EditorFor(x => x.Gender) 
    <p> 
     <input type="submit" value="Create" /> 
    </p> 
} 

오류 :

Server Error in '/' Application. 

The model item passed into the dictionary is null, but this dictionary requires a non-null model item of type 'MvcTest.Models.Gender'. 

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.InvalidOperationException: The model item passed into the dictionary is null, but this dictionary requires a non-null model item of type 'MvcTest.Models.Gender'. 

Source Error: 


Line 3: { 
Line 4:  
Line 5:  @Html.EditorFor(x => x.Gender) 
Line 6:  <p> 
Line 7:   <input type="submit" value="Create" /> 

Source File: e:\MvcTest\MvcTest\Views\Home\Create.cshtml Line: 5 

Stack Trace: 


[InvalidOperationException: The model item passed into the dictionary is null, but this dictionary requires a non-null model item of type 'MvcTest.Models.Gender'.] 
    System.Web.Mvc.ViewDataDictionary`1.SetModel(Object value) +143 
    System.Web.Mvc.ViewDataDictionary..ctor(ViewDataDictionary dictionary) +377 
    System.Web.Mvc.WebViewPage`1.SetViewData(ViewDataDictionary viewData) +27 
    System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +99 
    System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +115 
    System.Web.Mvc.Html.TemplateHelpers.ExecuteTemplate(HtmlHelper html, ViewDataDictionary viewData, String templateName, DataBoundControlMode mode, GetViewNamesDelegate getViewNames, GetDefaultActionsDelegate getDefaultActions) +584 
    System.Web.Mvc.Html.TemplateHelpers.TemplateHelper(HtmlHelper html, ModelMetadata metadata, String htmlFieldName, String templateName, DataBoundControlMode mode, Object additionalViewData, ExecuteTemplateDelegate executeTemplate) +1027 
    System.Web.Mvc.Html.TemplateHelpers.TemplateHelper(HtmlHelper html, ModelMetadata metadata, String htmlFieldName, String templateName, DataBoundControlMode mode, Object additionalViewData) +66 
    System.Web.Mvc.Html.TemplateHelpers.TemplateFor(HtmlHelper`1 html, Expression`1 expression, String templateName, String htmlFieldName, DataBoundControlMode mode, Object additionalViewData, TemplateHelperDelegate templateHelper) +118 
    System.Web.Mvc.Html.TemplateHelpers.TemplateFor(HtmlHelper`1 html, Expression`1 expression, String templateName, String htmlFieldName, DataBoundControlMode mode, Object additionalViewData) +100 
    System.Web.Mvc.Html.EditorExtensions.EditorFor(HtmlHelper`1 html, Expression`1 expression) +57 
    ASP._Page_Views_Home_Create_cshtml.Execute() in e:\MvcTest\MvcTest\Views\Home\Create.cshtml:5 
    System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +207 
    System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +81 
    System.Web.WebPages.StartPage.RunPage() +19 
    System.Web.WebPages.StartPage.ExecutePageHierarchy() +65 
    System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +76 
    System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +220 
    System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +115 
    System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +303 
    System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13 
    System.Web.Mvc.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19() +23 
    System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) +260 
    System.Web.Mvc.<>c__DisplayClass1e.<InvokeActionResultWithFilters>b__1b() +19 
    System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) +177 
    System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +343 
    System.Web.Mvc.Controller.ExecuteCore() +116 
    System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +97 
    System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +10 
    System.Web.Mvc.<>c__DisplayClassb.<BeginProcessRequest>b__5() +37 
    System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +21 
    System.Web.Mvc.Async.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _) +12 
    System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62 
    System.Web.Mvc.<>c__DisplayClasse.<EndProcessRequest>b__d() +50 
    System.Web.Mvc.SecurityUtil.<GetCallInAppTrustThunk>b__0(Action f) +7 
    System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +22 
    System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +60 
    System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9 
    System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8862381 
    System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +184 

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.225 

질문 : Create.cshtml 때의 EditorFor (X = x.Prop)에 의해 생성 된 널 (null) 예외를 방지하는 방법 모델 클래스의 인스턴스가 뷰에 전달되지 않습니까?

Answer 1

AFAIK이 작업을 수행하려면 nullable enum을 사용해야합니다. 또한 값이 선택되지 않으면 (--SELECT--) 열거 형이 null이어야하기 때문에 의미가 있습니다. 유용한 확장 방법에 대한 설명은 nice blog post입니다.