没有“IEnumerable<SelectListItem>"类型的 ViewData 项有键'xxx' [英] There is no ViewData item of type &#39;IEnumerable&lt;SelectListItem&gt;&#39; that has the key &#39;xxx&#39;

问题描述

在 Stack Overflow 上有几篇关于这个的帖子，但没有一个答案似乎可以解决我目前的情况.

There are a couple of posts about this on Stack Overflow but none with an answer that seem to fix the problem in my current situation.

我有一个带有表格的页面，每一行都有许多文本字段和一个下拉列表.所有下拉菜单都需要使用相同的 SelectList 数据，因此我将其设置如下:

I have a page with a table in it, each row has a number of text fields and a dropdown. All the dropdowns need to use the same SelectList data so I have set it up as follows:

控制器

ViewData["Submarkets"] = new SelectList(submarketRep.AllOrdered(), "id", "name");

查看

<%= Html.DropDownList("submarket_0", (SelectList)ViewData["Submarkets"], "(none)") %>

我在很多地方都使用过这个设置，但由于某种原因在这个特定的视图中我得到了错误:

I have used exactly this setup in many places, but for some reason in this particular view I get the error:

没有键为submarket_0"的IEnumerable"类型的 ViewData 项.

推荐答案

好的，所以答案来自其他一些关于这个问题的帖子，它是:

Ok, so the answer was derived from some other posts about this problem and it is:

如果您的 ViewData 包含与您的 DropDownList 同名的 SelectList，即submarket_0"，Html 助手将自动填充您的 DropDownList 使用该数据如果您不指定第二个参数，在本例中为源 SelectList.

If your ViewData contains a SelectList with the same name as your DropDownList i.e. "submarket_0", the Html helper will automatically populate your DropDownList with that data if you don't specify the 2nd parameter which in this case is the source SelectList.

我的错误发生了什么:

因为包含下拉列表的表格在局部视图中并且 ViewData 已更改并且不再包含我引用的 SelectList，HtmlHelper(而不是抛出错误)试图在它仍然找不到的 ViewData (GRRRR!!!) 中找到名为submarket_0"的 SelectList，然后抛出一个错误:)

Because the table containing the drop down lists was in a partial view and the ViewData had been changed and no longer contained the SelectList I had referenced, the HtmlHelper (instead of throwing an error) tried to find the SelectList called "submarket_0" in the ViewData (GRRRR!!!) which it STILL couldnt find, and then threw an error on that :)

如果我错了请纠正我

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