关于c＃：对象引用未设置为布局页面上对象的实例

Object reference not set to an instance of an object on layout page

我在编辑页中有一个编辑表单。当我第一次进入该页时，一切都正常。但提交表单后，我看到以下错误：

Object reference not set to an instance of an object. 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.NullReferenceException: Object reference not
set to an instance of an object.

在源代码错误中，您可以看到：

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@{
ViewBag.Title ="Edit";
Layout ="~/Views/Shared/_Layout.cshtml";
}

现在怎么了？！

更新

我的观点代码：

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@model Portal.Web.CMS.Models.PageViewModel

@{
ViewBag.Title ="?????? ????";
Layout ="~/Views/Shared/_Layout.cshtml";
}

????
<ul class="breadcrumb" style="background-color: white;">

<li>
???? ????? <span class="divider">/</span>
</li>

<li>
@Model.Name <span class="divider">/</span>
</li>

<li class="active">?????? ????
</li>

</ul>

@using (Html.BeginForm())
{
@Html.ValidationSummary(true)

@Html.HiddenFor(model => model.PageId)

@Html.LabelFor(model => model.Lang)

@if (Model.Lang.ToString() =="Fa")
{
<button type="button" value="2" class="btn">English</button>
<button type="button" value="1" class="btn active">?????</button>
}
else
{
<button type="button" value="2" class="btn active">English</button>
<button type="button" value="1" class="btn">?????</button>
}

@Html.Hidden("Lang")

@Html.LabelFor(model => model.Name)

@Html.EditorFor(model => model.Name)
@Html.ValidationMessageFor(model => model.Name)

@Html.LabelFor(model => model.Url)

@Html.EditorFor(model => model.Url)
@Html.ValidationMessageFor(model => model.Url)

@Html.LabelFor(model => model.Title)

@Html.EditorFor(model => model.Title)
@Html.ValidationMessageFor(model => model.Title)

@Html.LabelFor(model => model.PageContent)

@Html.TextAreaFor(model => model.PageContent)
@Html.ValidationMessageFor(model => model.PageContent)

<p>

<button type="button" id="addFile" class="btn btn success">???? ?????</button>

</p>
<p>

<input type="file" name="files" />

</p>

<p>

<button type="button" id="addPicture" class="btn btn success">??? ?????</button>

</p>
<p>

<input type="file" name="images" />

</p>

if (Model.PageAttachements!=null )
{
<fieldset>
<legend>???? ??? ?????</legend>

@foreach (var file in Model.PageAttachements)
{

×
@file.Name

}

</fieldset>
}
if (Model.PageImages.Count > 0)
{
<fieldset>
<legend>?????? ?????</legend>

@foreach (var image in Model.PageImages)
{

×
<img src="~/Images/@image.Name" />

}

</fieldset>
}
<p>

<input type="submit" value="?????" class="btn btn-primary btn-large" />

</p>
}

@section Scripts {
@Scripts.Render("~/bundles/jqueryval")
}

控制器：

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public ActionResult Edit(int id)
{
var model = Mapper.Map<PageViewModel>(pageApp.GetPageById(id));
return View(model);
}
[HttpPost]
public ActionResult Edit(PageViewModel model)
{
bool result = false;
if (model.Lang.ToString() =="Fa")
result = pageApp.IsRepetitive(model.Url, 1);
else
result = pageApp.IsRepetitive(model.Url, 2);
if (result == true)
{
TempData["error"] ="???? ?? ?? ???? ???? ? ???? ???? ????.";
return View();
}
else
{
if (model.PageContent != null)
{
var page = Mapper.Map<Page>(model);
page.UserId = Portal.Web.CMS.Components.SessionContext.GetUserData().UserId;
page.PageDate = DateTime.Now;
pageApp.Update(page);
TempData["success"] ="???? ?? ?????? ????? ????.";
return RedirectToAction("Details", new { url = model.Url });
}
else
{
TempData["error"] ="????? ???.???? ???? ?? ???? ???.";
return View();
}
}
}