Question

如果ModelState无效，我试图保持dropdownlist选择值

因为我想保留用户选择的数据，即使ModelState不是有效

我的代码看起来像这样

获取方法：

  [HttpGet]
        public ActionResult Edit(int? Id)
        {
            using (var db = new NewsDatabaseEntities())
            {
                db.Configuration.LazyLoadingEnabled = false;

                var Result = (from n in db.News.Include("Categories")
                              from c in db.Categories
                              where n.NewsId == Id
                              select new { news = n, neweCategories = n.Categories, cate = c }).ToList();


                News NewsDetails = (from news in Result
                                    select new News
                                    {
                                        NewsId = news.news.NewsId,
                                        NewsTitle = news.news.NewsTitle,
                                        NewsBody = news.news.NewsBody,
                                        NewsImagePath = news.news.NewsImagePath,
                                        Categories = news.neweCategories
                                    }).FirstOrDefault();

                var AllCategories = (from c in Result
                                     select new Category
                                     {
                                         CategoryId = c.cate.CategoryId,
                                         CategoryName = c.cate.CategoryName
                                     }).ToList();



                if (NewsDetails != null)
                {

                    var model = new NewsViewModel();
                    model.NewsId = NewsDetails.NewsId;
                    model.AllCategories = AllCategories;
                    model.Categories = NewsDetails.Categories;
                    model.NewsTitle = NewsDetails.NewsTitle;
                    model.NewsBody = NewsDetails.NewsBody;
                    model.NewsImagePath = NewsDetails.NewsImagePath;





                    Session["AllCategories"] = new MultiSelectList(AllCategories, "CategoryId", "CategoryName", model.Categories.Select(J => J.CategoryId).ToArray());
                    Session["model"] = model;
                    return View(model);
                }
                else
                {
                    return RedirectToAction("Index", "Home");
                }
            }
            return View();
        }

发布方法：

        [HttpPost]
        [ValidateInput(false)]
        public ActionResult Edit(NewsViewModel model,FormCollection col)
        {



            if (!ModelState.IsValid)
            {
                model = (NewsViewModel)Session["model"];

                return View(model);
            }

查看：

     @Html.DropDownListFor(c => c.SelectedCategoriesIds, (MultiSelectList)Session["AllCategories"], new { id = "DropDownList1", multiple = "multiple", @class = "form-control" })

Answer 1

因为您正在使用您在GET操作中设置的会话数据覆盖视图模型对象（具有所选选项值）。

您应该将选定的选项值读取到临时变量并使用它。

 [HttpPost]
 [ValidateInput(false)]
 public ActionResult Edit(NewsViewModel model,FormCollection col)
 {
    if (!ModelState.IsValid)
    {   
       var selected=  model.SelectedCategoriesIds;
       model = (NewsViewModel)Session["model"];
       model.SelectedCategoriesIds =selected;
       return View(model);
    } 
    //save and return something**strong text**
}

更好的解决方案不是在这里使用会话。您可以从db表/缓存中再次读取值。同样，为了呈现下拉列表，您可以简单地向视图模型添加属性并使用它。

public class NewsViewModel
{
  public List<SelectListItem> AllCategories {set;get;}
  //Other properties
}

并且在您的GET操作中，不是将类别设置为Session，而是将其设置为此属性

public ActionResult  Edit(int? id)
{
  var vm = new NewsViewModel();

  vm.AllCategories = GetCategories();
  return View(vm);
}

private IEnumerable<SelectListItem> GetCategories()
{
   return db.Categories
            .Select(s=>new SelectListItem { Value=s.Id.ToString(), 
                                            Text=s.Name).ToList();
}

并在您的视图中

@model NewsViewModel 
@using(Html.BeginForm())
{
     <label> Select items <label>
   @Html.ListBoxFor(s=>s.SelectedCategoriesIds,AllCategories )
   <input type="submit" />
}

现在在您的HttpPost操作中，当模型验证失败时，您不需要使用会话，只需调用相同的方法来重新加载AllCategories属性。

if (!ModelState.IsValid)
{ 
     model.AllCategories=GetCategories();      
     return View(model);
}

如果ModelState无效，如何保持dropdownlist选择值

1 个答案: