這是我的組合模型:ASP.NET MVC DropdownlistFor對象引用未設置爲對象的實例?
public class AddArticleModel
{
public TBL_ARTICLES Article { get; set; }
public IEnumerable<TBL_CATEGORIES> Categories { get; set; }
}
和控制器,它使用模式。
public ActionResult AddArticle()
{
AddArticleModel AddArticleModel = new AddArticleModel();
AddArticleModel.Categories = entity.TBL_CATEGORIES.Select(a => a);
return View(AddArticleModel);
}
,並查看:
@model DunyaYazilim.Models.AddArticleModel
@{
ViewBag.Title = "AddArticle";
}
@using (Html.BeginForm((string)ViewBag.FormAction, "Home"))
{
<fieldset>
<legend>Add Article Form</legend>
<ol>
<li>
@Html.DropDownListFor(m => m.Categories, Model.Categories.Select(c => new SelectListItem { Text = c.Name, Value = c.CategoryID.ToString() }), "-----Select Category----")
</li>
</ol>
<input type="submit" value="Send" />
</fieldset>
}
,並張貼方法控制器:
[HttpPost]
public ActionResult AddArticle(AddArticleModel AddArticleModel)
{
//Insert operations:
return View(AddArticleModel);
}
我的問題:當我張貼的形式,出現錯誤:對象引用未設置爲一個實例的一個對象。在線:13
Line 12: <li>
Line 13: @Html.DropDownListFor(m => m.Categories, Model.Categories.Select(c => new SelectListItem { Text = c.Name, Value = c.CategoryID.ToString() }), "-----Select Category----")
Line 14: </li>
Line 15: <li>
這是什麼原因?
注:本網站有很多檢查。我嘗試了很多,但我找不到錯誤的原因。
謝謝。
可能重複[什麼是NullReferenceException,以及如何解決它?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-doi-i-fix -it) – 2017-01-11 10:28:36