MVC 3 Dropdownlist用於搜索的鏈接模態查看列表在回發中始終爲空

Question

我有一個帶有過濾器的搜索表單。 1過濾器是範圍，這是一個數字下拉。我有一個視圖使用一個查看範圍（我的數據庫表）ienumerable視圖和控制器我填充這個和所有的作品，因爲它應該...直到表單顯示，用戶試圖再次過濾，在這種情況下，我的模型視圖ienumerable現在爲null。爲什麼它會失去價值。我是否需要每次用戶重新設置一次新的過濾器......如果可以，不需要重複調​​用數據庫，因爲下拉列表中的值不會改變。

模式的看法

public class SearchResultsViewModel 
{ 
    public int? Page { get; set; } 
    public penguin.Models.Job Job { get; set; } 
    public IPagedList<Models.Job> SearchResults { get; set; } 
    public string SearchButton { get; set; } 

    [Display(Name = "keywords")] 
    public string keywords { get; set; } 
    [Display(Name = "location")] 
    public string location { get; set; } 
    public int RangeID { get; set; } 
    public IEnumerable<Models.SearchRange> Range { get; set; } 

} 

控制器

const int RecordsPerPage = 25; 
    public ActionResult Jobs(ViewModels.SearchResultsViewModel model) 
    { 

     // do something with the search value      
     if (!string.IsNullOrEmpty(model.SearchButton) || model.Page.HasValue) 
     { 

      var entities = new Models.DBDataContext(); 
      var results = entities.Jobs; 

      var pageIndex = model.Page ?? 1; 
      model.SearchResults = results.ToPagedList(pageIndex, 25); 

      //Range = ViewData["Range"] as IEnumerable<Models.SearchRange>; 
     } 
     else { 
      var Data = Helpers.ModelHelpers.GetDataContext(); 
      var ranges = (from r in Data.SearchRanges select r); 
      model.Range = ranges; 
      //Range = ranges; 

     } 
     //ViewData["Range"] = Range; 
     //model.Range = Range; 
     return View(model); 


    } 

查看

@using PagedList.Mvc; 
@model ViewModels.SearchResultsViewModel   
@{ 
    ViewBag.Title = "Jobs"; 
} 
@section search { 
@using (Html.BeginForm("Jobs", "Search", FormMethod.Post, new { id = "searchForm" })) 
{ 
    <fieldset> 
     @Html.LabelFor(m => m.keywords) 
     @Html.TextBoxFor(m => m.keywords) 
     @Html.LabelFor(m => m.location) 
     @Html.TextBoxFor(m => m.location) 

     @Html.DropDownListFor(m => m.RangeID, new SelectList(Model.Range, "ID", "Range", 5)) 
     <input name="SearchButton" type="submit" value="Search" /> 
    </fieldset> 

    } 
} 
<h2> 
Jobs</h2> 
<div id="resultContainer"> 
my paged results set will go in here with a link to view job details. I then want 
it to come back here and not lose anything 
@* html.Action("Results", "Search")*@ 
@if (Model.SearchResults != null && Model.SearchResults.Count > 0) 
{ 
    foreach (var result in Model.SearchResults) 
    { 
    <hr /> 
    <table width="100%"> 
     <tr> 
      <td valign="top"> 
       <div style="font-weight: bold; font-size: large;"> 
        @Html.Raw(@result.Title.Truncate(50))</div> 
       @Html.Raw(@result.summary.Truncate(50))<br /> 
       </td> 
        </tr> 
    </table> 

    } 

    <hr />   

    @Html.PagedListPager(Model.SearchResults, page => Url.Action("Jobs", new RouteValueDictionary() { 
       { "Page", page }, 
       { "Job", Model.Job } 
       }), PagedListRenderOptions.DefaultPlusFirstAndLast)} 
    </div> 

Answer 1

如果下拉列表中的值不會改變（曾經），那麼你可能應該緩存它們服務器端，每次只重用這些值。您將需要每次向模型提供值，因爲數據不會在連續請求之間持續存在。 MVC中沒有視圖狀態來保留這些值。實際上，這是一件好事。

private static IEnumerable SearchRange { get; set; } 

static SearchController() 
{ 
    SearchRange = new MyDataContext().SearchRanges.AsEnumerable(); 
} 

public ActionResult Jobs(ViewModels.SearchResultsViewModel model) 
{ 
    model.Range = SearchRange; 
    ... 
}