DROPDOWNLIST在MVC3剃刀设置选定的值 [英] dropdownlist set selected value in MVC3 Razor

问题描述

下面是我的模型：

public class NewsCategoriesModel {
    public int NewsCategoriesID { get; set; }        
    public string NewsCategoriesName { get; set; }
}

我的控制器：

public ActionResult NewsEdit(int ID, dms_New dsn) {
    dsn = (from a in dc.dms_News where a.NewsID == ID select a).FirstOrDefault();
    var categories = (from b in dc.dms_NewsCategories select b).ToList();
    var selectedValue = dsn.NewsCategoriesID;
    SelectList ListCategories = new SelectList(categories, "NewsCategoriesID", "NewsCategoriesName",selectedValue);

    // ViewBag.NewsCategoriesID = new SelectList(categories as IEnumerable<dms_NewsCategory>, "NewsCategoriesID", "NewsCategoriesName", dsn.NewsCategoriesID);
    ViewBag.NewsCategoriesID = ListCategories;
    return View(dsn);
}

然后我的看法：

@Html.DropDownList("NewsCategoriesID", (SelectList)ViewBag.NewsCategoriesID)

当我运行时，的DropDownList 不选择我设置的值。它总是选择第一个选项。

When i run, the DropDownList does not select the value I set.. It is always selecting the first option.

推荐答案

您应该使用视图模型，而忘记了 ViewBag 想想它，好像它不存在。你会看到更容易的事情怎么会变成。所以定义视图模型：

You should use view models and forget about ViewBag Think of it as if it didn't exist. You will see how easier things will become. So define a view model:

public class MyViewModel
{
    public int SelectedCategoryId { get; set; }
    public IEnumerable<SelectListItem> Categories { get; set; } 
}

和然后填充这个视图控制器模型：

and then populate this view model from the controller:

public ActionResult NewsEdit(int ID, dms_New dsn)
{
    var dsn = (from a in dc.dms_News where a.NewsID == ID select a).FirstOrDefault();
    var categories = (from b in dc.dms_NewsCategories select b).ToList();

    var model = new MyViewModel
    {
        SelectedCategoryId = dsn.NewsCategoriesID,
        Categories = categories.Select(x => new SelectListItem
        {
            Value = x.NewsCategoriesID.ToString(),
            Text = x.NewsCategoriesName
        })
    };
    return View(model);
}

终于在您的视图中使用强类型 DropDownListFor 助手：

@model MyViewModel

@Html.DropDownListFor(
    x => x.SelectedCategoryId,
    Model.Categories
)

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