我试图制作一个简单的asp.net-mvc应用程序。我已经制作了我的模型类并将其添加到数据库中。我使用内置方法使用Entity Framework生成带有视图的控制器。但出于某种原因，当我尝试查看Create页面（并且只有Create页面，而不是编辑页面！）时，我得到一个Null Reference Exception（对象引用未设置为对象的实例）。
所以我的创建行动：
public ActionResult Create()
{
return View();
}
这是我的编辑操作：
public ActionResult Edit(int? id)
{
if (id == null)
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
SupplierCorrection supplierCorrection = db.SupplierCorrectionSet.Find(id);
if (supplierCorrection == null)
{
return HttpNotFound();
}
return View(supplierCorrection);
}
这是我的创建页面：
@model FAIR.Data.Models.SupplierCorrection
@{
ViewBag.Title = "Create";
}
<h2>Create</h2>
@using (Html.BeginForm())
{
@Html.AntiForgeryToken()
<div class="form-horizontal">
<h4>SupplierCorrection</h4>
<hr />
@Html.ValidationSummary(true, "", new { @class = "text-danger" })
@Html.Partial("_createEdit", Model)
<div class="form-group">
<div class="col-md-offset-2 col-md-10">
<input type="submit" value="Save" class="btn btn-default" />
</div>
</div>
</div>
}
<div>
@Html.ActionLink("Back to List", "Index")
</div>
@section scripts{
<script type="text/javascript" src="~/Scripts/SupplierCorrectionsCreateEdit.js"></script>
}
这是我的编辑页面（精明的读者会注意到它非常相似）：
@model FAIR.Data.Models.SupplierCorrection
@{
ViewBag.Title = "Edit";
}
<h2>Edit</h2>
@using (Html.BeginForm())
{
@Html.AntiForgeryToken()
<div class="form-horizontal">
<h4>SupplierCorrection</h4>
<hr />
@Html.ValidationSummary(true, "", new { @class = "text-danger" })
@Html.HiddenFor(model => model.ID)
@Html.Partial("_createEdit", Model)
<div class="form-group">
<div class="col-md-offset-2 col-md-10">
<input type="submit" value="Save" class="btn btn-default" />
</div>
</div>
</div>
}
<div>
@Html.ActionLink("Back to List", "Index")
</div>
@section scripts{
<script type="text/javascript" src="~/Scripts/SupplierCorrectionsCreateEdit.js"></script>
}
和这里的_createEdit：
@model FAIR.Data.Models.SupplierCorrection
<div class="form-group">
@Html.LabelFor(model => model.FAIRNumber, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.EditorFor(model => model.FAIRNumber, new { htmlAttributes = new { @class = "form-control" } })
@Html.ValidationMessageFor(model => model.FAIRNumber, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
@Html.LabelFor(model => model.Supplier, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.EditorFor(model => model.Supplier, new { htmlAttributes = new { @class = "form-control" } })
@Html.ValidationMessageFor(model => model.Supplier, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
@Html.LabelFor(model => model.Closed, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
<div class="checkbox">
@Html.EditorFor(model => model.Closed)
@Html.ValidationMessageFor(model => model.Closed, "", new { @class = "text-danger" })
</div>
</div>
</div>
<div class="form-group">
<label class="control-label col-md-2">Corrections Link</label>
<div class="col-md-10">
<input type="file" id="CorrectionsLinkFilePicker" onchange="CorrectionsLinkChosen();" />
<input type="hidden" name="CorrectionsLink" id="CorrectionsLink" value="@Model.CorrectionsLink" />
@if (!string.IsNullOrWhiteSpace(Model?.CorrectionsLink))
{
@:Currently: <a href="@Model.CorrectionsLink">@Model.CorrectionsLink</a>
}
@Html.ValidationMessageFor(model => model.CorrectionsLink, "", new { @class = "text-danger" })
</div>
</div>
当我导航到“创建”页面（再次，而不是编辑页面）时，它在第24行出现错误，我在那里Html.ValidationMesageFor(model => model.Closed, ...但是如果我删除它，则会在上一行中出错。依此类推，直到我using(Html.BeginForm())为止。我想作为权宜之计，我可以在不使用Html对象的情况下重写页面，但如果再次发生这种情况（或在较长的页面上），我想知道为什么它在世界上突然去了。
完整堆栈跟踪：
at ASP._Page_Views_SupplierCorrections__createEdit_cshtml.Execute() in C:\Users\ttm920632\Desktop\Repos\FAIR\FAIR\Views\SupplierCorrections\_createEdit.cshtml:line 24
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 System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model)
at ASP._Page_Views_SupplierCorrections_Create_cshtml.Execute() in C:\Users\ttm920632\Desktop\Repos\FAIR\FAIR\Views\SupplierCorrections\Create.cshtml:line 18
at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
at System.Web.WebPages.StartPage.RunPage()
at System.Web.WebPages.StartPage.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.ViewResultBase.ExecuteResult(ControllerContext context)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult)