ASP.NET MVC的DropDownList

问题描述

有人点我到显示DropDownList的LINQ从人口正在向SQL（文本和值被设置）。

Can someone point me to an article that shows the dropdownlist being populated from linq to sql (text and value being set).

谢谢
丹尼

推荐答案

现在的的HtmlHelper扩展需要一个的IEnumerable＆LT; SelectListItem＆GT; ，我没有创建的SelectList的，但通常只是创建SelectListItems使用LINQ。

Now that the HtmlHelper extension takes an IEnumerable<SelectListItem>, I don't create SelectList's, but usually just create the SelectListItems with LINQ.

控制器

ViewData["CategoryID"] = categories.Select( c => new SelectListItem
                                                 {
                                                     Text = c.CategoryName,
                                                     Value = c.CategoryID
                                                 }
                                          );

查看

<%= Html.DropDownList("CategoryID") %>

如果我想要一个默认选项

or if I want a default selection

<%= Html.DropDownList("CategoryID",
                      (IEnumerable<SelectListItem>)ViewData["CategoryID"],
                      "Select a Category" ) %>

修改

有关下拉列表中的有趣的一点是，你需要提供一系列从数值来选择适合你的实际的数据模型的单一值。我通常提供通过查看数据的范围（菜单项），并在页面张贴期待后面的模型值。如果你想强类型的菜单，以及，你需要提供你的封装了真正的模型和任何菜单仅查看模式。这将涉及上张贴，使用prefixes的识别模型元素。权衡，在我看来，就是简单的模型与视图中使用强类型的菜单上后绑定。我不挂了后者，所以我选择不把我的菜单，在模型中。如果你想这样做，但是，它可能看起来像下面这样。

The interesting bit about the dropdown list is that you need to supply a range of values from which to select a single value that fits into your actual data model. I typically provide the range (menu items) via view data and expect back the model values when the page is posted. If you wanted strongly-typed menus as well, you'd need to provide a view-only model that encapulates your real model and any menus. This would involve, on posting, the use of prefixes to identify the model elements. The trade-off, to my mind, is simpler model binding on post vs. the use of strongly-typed menus in the view. I'm not hung up on the latter, so I opt not to put my menus in the model. If you wanted to do this, though, it might look like the following.

型号

public class CategoryViewModel
{
    public Category Category { get; set; }
    public IEnumerable<SelectListItem> CategoryMenu { get; set; }
    ...
}

控制器

的显示动作的

var model = new CategoryViewModel();
model.CategoryMenu = categories.Select( c => new SelectListItem
                                                 {
                                                     Text = c.CategoryName,
                                                     Value = c.CategoryID
                                                 }
                                      );

...
return View(model);

的创建行动的

[AcceptVerbs( HttpVerbs.Post )]
public ActionResult Create( [Bind(Prefix="Category")]Category category )
{
   ...
}

查看

<%= Html.TextBox("Category.Name") %>

<%= Html.DropDownList("Category.CategoryID",
                      Model.CategoryMenu,
                      "Select a Category" ) %>

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