黄兵的个人博客

ASP.NET MVC 让@Html.DropDownList显示默认值

在使用@Html.DropDownList的过程中，发现它的用法很局限，比如在加载的时候显示设定的默认项或者调整它的显示样式，在网上查了一些资料，终于把这个问题解决了。

前端代码如下：

<div class="hr-line-dashed FirstProject"></div>
<div class="form-group FirstProject">
    @Html.LabelFor(model => model.FirstProject, new { @class = "control-label col-md-2" })
    <div class="col-sm-10">
        @Html.DropDownList("FirstProId", ViewData["firstItem"] as SelectList,new { @class = "form-control" })
        @Html.ValidationMessageFor(model => model.FirstProject, "", new { @class = "text-danger" })
    </div>
</div>
<div class="hr-line-dashed SecondProject"></div>
<div class="form-group SecondProject">
    @Html.LabelFor(model => model.SecondProject, new { @class = "control-label col-md-2" })
    <div class="col-sm-10">
        @Html.DropDownList("SecondProId", ViewData["SecondItem"] as SelectList, new { @class = "form-control" })
        @Html.ValidationMessageFor(model => model.SecondProject, "", new { @class = "text-danger" })
    </div>
</div>

后端代码如下：

public ActionResult EditArticle(int? Id)
{
    if (Id == 0)         
        return RedirectToAction("Index", "Home", new { area = "" });
    else
        using(UnitOfWork uow=new UnitOfWork())
        {
            var ArticleItem=uow.ArticleRepository.Get(x=>x.Id==Id);
            BlogAddArticleViewModel ArticleModel = new BlogAddArticleViewModel();
            ArticleModel.Id = ArticleItem.Id;
            ArticleModel.Title = ArticleItem.Title;
            ArticleModel.ImgUrl = ArticleItem.ImgUrl;
            ArticleModel.Keyword = ArticleItem.SEO.Keyword;
            ArticleModel.Description = ArticleItem.SEO.Description;
            ArticleModel.Body = ArticleItem.ArticleBody;
            ArticleModel.SEO_Id = ArticleItem.SEOId;
            ArticleModel.CreationTime = ArticleItem.CreateTime;
            ArticleModel.News = ArticleItem.News;
        
            //查询作者
            var authories = uow.AuthorRepository.GetAll().ToList();
            ViewData["authories"] = new SelectList(authories, "Id", "AuhtorName");

            //查询第一个项目
            var firstItem = uow.FirstProjectRepository.GetAll().ToList();
            ViewData["firstItem"] = new SelectList(firstItem, "Id", "FirstProName");

            //查询第二个项目
            var SecondItem = uow.SecondProjectRepository.GetAll().Where(x=>x.FirstProId==ArticleItem.FirstProject).ToList();
            var DefaultItem=SecondItem.Where(x=>x.Id==ArticleItem.SecondProject);
            ViewData["SecondItem"] = new SelectList(SecondItem, "Id", "SecondProName",DefaultItem);

            return View(ArticleModel);
        }
}

注意这里两行：

var DefaultItem=SecondItem.Where(x=>x.Id==ArticleItem.SecondProject);
ViewData["SecondItem"] = new SelectList(SecondItem, "Id", "SecondProName",DefaultItem);

DefaultItem是要默认显示的项。

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