记录：.net mvc中DropDownListFor和selectList的使用

category类代码：

public partial class Category
    {
        public int CategoryId { get; set; }
        public int CategoryTypeId { get; set; }
        public string CategroyTitle { get; set; }
        public int ParentId { get; set; }
    }

News类代码：

 public partial class News
    {
        public int Id { get; set; }
        public int CategoryId { get; set; }
        public int UserId { get; set; }
        public string Title { get; set; }
        public string Author { get; set; }
        public string Form { get; set; }
        public string Content { get; set; }
        public int SortId { get; set; }
        public Nullable<int> Clicks { get; set; }
        public bool IsLock { get; set; }
        public System.DateTime AddTime { get; set; }
    }

 

在News页面中显示所属分类下拉列表,下拉列表的value值和文本字段分别来自category表中的CategoryId和CategoryTitle

action方法中定义一个匿名类List，并绑定分类表（category）中的数据,因为下拉列表只要category表中的CategoryId和CategoryTitle的值，所以匿名List只需定义这两属性，注意：匿名List此时不需转换成SelectList

代码如下：

public ActionResult News()
        {
           List<Category>categoryList=base.CategoryBLL.Where().ToList();
            ViewBag.selectList= categoryList.Select(c => new { id = c.CategoryId, name = c.CategroyTitle });
            List<NewsView>newsList= AutoEntityMap<News,NewsView>.EntityMap(base.NewsBLL.Where().ToList());
            return View(newsList);
        }

视图中利用DropDownListFor()显示列表代码如下：

@foreach (var item in Model)
                    {
                        var author=item.Author == null ? "佚名" : item.Author;
                        <tr>
                            <td><input type="checkbox" /></td>
                            <td>@Html.DisplayFor(Model => item.Id)</td>
                            <td><a href="#">@Html.DisplayFor(modelItmes => item.Title)</a></td>
                            <td>@Html.DropDownListFor(modelItmes => item.CategoryId, new SelectList(ViewBag.selectList,"id","name",item.CategoryId))</td>
                            <td class="am-hide-sm-only">@author</td>
                            <td class="am-hide-sm-only"></td>
                            <td>
                                <div class="am-btn-toolbar">
                                    <div class="am-btn-group am-btn-group-xs">
                                        <button class="am-btn am-btn-default am-btn-xs am-text-secondary"><span class="am-icon-pencil-square-o"></span> 编辑</button>
                                        <button class="am-btn am-btn-default am-btn-xs am-hide-sm-only"><span class="am-icon-copy"></span> 复制</button>
                                        <button class="am-btn am-btn-default am-btn-xs am-text-danger am-hide-sm-only"><span class="am-icon-trash-o"></span> 删除</button>
                                    </div>
                                </div>
                            </td>
                        </tr>
                    }

注意：“dataValueField”, “dataTextField”的名称必须与匿名List对象中的两个属性名相同；

 本例中用到的SelectList构造函数如下：

 //
        // 摘要:
        //     Initializes a new instance of the System.Web.Mvc.SelectList class by using the
        //     specified items for the list, the data value field, the data text field, and
        //     a selected value.
        //
        // 参数:
        //   items:
        //     The items.
        //
        //   dataValueField:
        //     The data value field.
        //
        //   dataTextField:
        //     The data text field.
        //
        //   selectedValue:
        //     The selected value.
        public SelectList(IEnumerable items, string dataValueField, string dataTextField, object selectedValue);