Question

我有一个使用PagedList的页面，但也包含用于排序的下拉列表。问题是，每当有人使用下拉列表项进行排序时，无论何时他们点击“下一步”或“后退”，下拉列表项都会恢复为默认值，程序将通过控制器运行默认（基本上为空白）排序标准，当您导航到第二页或更高页面（和返回页面）时，您会松开已排序的项目。

以下是此页面使用的控制器：

    public ActionResult Index(FormCollection dropDownSelection, string currentFilter, int? page)
    {
        //security
        if (!Security.IsViewer(User)) return RedirectToAction("Message", "Home", new { id = 2 });

        if (ViewBag.Level == 0) return RedirectToAction("Message", "Home", new { id = 2 });

        if (!(Request.HttpMethod == "GET"))
        {
            page = 1;
        }


        string table = String.IsNullOrWhiteSpace(dropDownSelection["Table"]) ? "%" : dropDownSelection["Table"];
        string issue = String.IsNullOrWhiteSpace(dropDownSelection["IssueType"]) ? "%" : dropDownSelection["IssueType"];
        string status = String.IsNullOrWhiteSpace(dropDownSelection["Status"]) ? "%" : dropDownSelection["Status"];

        var followUpItem = from follow in db.FollowUpItems
                           where (follow.TableName.Equals(table) || table.Equals("%")) &&
                                 (follow.IssueType.Equals(issue) || issue.Equals("%")) &&
                                 (follow.Status.Equals(status) || status.Equals("%"))
                           orderby follow.Id
                           select follow;

        int pageNumber = (page ?? 1);
        int pageSize = 10;

        return View(followUpItem.ToPagedList(pageNumber, pageSize));
    }

以下是View中的下拉列表：

          <select name="Table" title="Table" style="font-size:8pt;">
            <option value="%">--Table Name--</option>
            <option value="AgentContEd">CE</option>
            <option value="AgentProductTraining">PT</option>
          </select>
          <select name="IssueType" style="font-size:8pt;">
            <option value="%">--Issue Type--</option>
            <option value="W">Warning</option>
            <option value="E">Error</option>
          </select>
          <select name="Status" style="font-size:8pt;">
            <option value="%">--Status Type--</option>
            <option value="O">Open</option>
            <option value="U">Under Review</option>
          </select>

以下（以防万一）下面是包含View中的PagedList导航按钮的<div>：

<div>
Page @(Model.PageCount < Model.PageNumber ? 0 : Model.PageNumber)
of @Model.PageCount

@if (Model.HasPreviousPage)
{
    @Html.ActionLink("<<", "Index", new { page = 1, sortOrder = ViewBag.CurrentSort, searchString = ViewBag.CurrentFilter, currentFilter = ViewBag.CurrentFilter })
    @Html.Raw(" ");
    @Html.ActionLink("< Prev", "Index", new { page = Model.PageNumber - 1, sortOrder = ViewBag.CurrentSort, searchString = ViewBag.CurrentFilter, currentFilter = ViewBag.CurrentFilter })
}
else
{
    @:<<
    @Html.Raw(" ");
    @:< Prev
}

@if (Model.HasNextPage)
{
    @Html.ActionLink("Next >", "Index", new { page = Model.PageNumber + 1, sortOrder = ViewBag.CurrentSort, searchString = ViewBag.CurrentFilter, currentFilter = ViewBag.CurrentFilter })
    @Html.Raw(" ");
    @Html.ActionLink(">>", "Index", new { page = Model.PageCount, sortOrder = ViewBag.CurrentSort, searchString = ViewBag.CurrentFilter, currentFilter = ViewBag.CurrentFilter })
}
else
{
    @:Next >
    @Html.Raw(" ")
    @:>>
}
</div>

Answer 1

如果您首先通过ViewModel传递followUpItem然后实际传递下拉列表中的选定值，该怎么办？也许接近这个。

public ActionResult Index(FormCollection dropDownSelection, string currentFilter, int? page)
{
    //Stuff abbreviated 

    return View(new StuffViewModel(followUpItem.ToPagedList(pageNumber, pageSize)), "SelectedDropDownItem");
}

然后你可以在ViewModel中处理它，例如在内存中创建你自己的DropDownlist。这样的事情。

public class StuffViewModel
{
    public List<FollowUpItem> FollowUpItems {get; private set;}
    public List<SelectListItem> DropDownList {get; private set}

    public StuffViewModel(List<FollowUpItem> followUpItems, string selectedDropDownValue)
    {
        FollowUpItems = followUpItems;

        List<SelectListItem> selectList = new List<SelectListItem>();
        //TODO: here you would decide which is selected from the selectedDropDownValue parameter
        selectList.Add(new SelectListItem{ Selected = true, Text = "Text", Value = "Value" });
        selectList.Add(new SelectListItem{ Selected = false, Text = "Text2", Value = "Value2" });
        //...and more values as you need them

        DropDownList = selectList
    }
}

通过使用ViewModel执行此操作，无论您在pagedList中的哪个位置，您都将始终从每次单击的下拉列表中保留所选值。

请记住，您的View现在将包含一个包含StuffViewModel的模型，而不是仅包含PagedList。现在，您可以在视图中调用元素，如下所示：

@model StuffViewModel

//TODO: access dropdownlist
@Html.DropDownList("name", Model.DropDownList)

//TODO: access PagedList for instenace like this:
if(Model.FollowUpItems.HasPreviousPage)
{
    //do stuff
}

我希望我有道理：）

Answer 2

这很简单。您没有坚持下拉选项。分页链接需要包含当前的下拉选项，这样当您向下一页提交GET请求时，数据将在查询字符串中传递，以用于呈现视图。

使用PagedList时，从控制器设置ASP MVC3下拉列表项

2 个答案: