下拉列表在 MVC3 Razor 中设置选定的值 [英] dropdownlist set selected value in MVC3 Razor

问题描述

这是我的模型:

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);
}

然后是我的观点:

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

当我运行时，DropDownList 没有选择我设置的值.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

你应该使用视图模型而忘记 ViewBag 把它想象成它不存在.你会看到事情会变得多么容易.所以定义一个视图模型:

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; } 
}

然后从控制器填充这个视图模型:

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);
}

最后在您的视图中使用强类型 DropDownListFor 助手:

and finally in your view use the strongly typed DropDownListFor helper:

@model MyViewModel

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

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