Question

我正在根据书的出版日期和关键词搜索参数对书籍索引进行排序。我正在使用一个switch语句，该语句选择枚举值，这些枚举值将以不同的顺序（按升序还是降序）告诉操作指令。但是，似乎Orderby不起作用，但是第一个case语句确实起作用。无论如何，该程序只会按照最新的顺序排序。最旧的优先不起作用。

public IActionResult Index(String SearchString, Classification DateValueSign)
    {


        var query = from r in _db.Books select r;

        if (SearchString != null && SearchString != "")
        {
            query = query.Where(x => x.Title.Contains(SearchString) || x.Author.Contains(SearchString) || x.Genre.GenreName.Contains(SearchString));

        }
        switch (DateValueSign)
        {
            case Classification.NewestFirst:
                query = query.OrderByDescending(x => x.PublicationDate);
                break;
            case Classification.OldestFirst:
                query = query.OrderBy(x => x.PublicationDate);
                break;
            case Classification.MostPopular:
                query = query.OrderByDescending(x => x.AverageRating);
                break;
            case Classification.LeastPopular:
                query = query.OrderBy(x => x.AverageRating);
                break;
        }
        List<Book> SelectedBooks = new List<Book>();
        SelectedBooks = query.ToList();
        ViewBag.SelectedBooks = SelectedBooks.Count();
        ViewBag.TotalBooks = _db.Books.Count();

        return View(SelectedBooks);
    }

这是索引视图。快速搜索位于索引页面上。

@model IEnumerable<fa18team16BevoBookStore.Models.Book>
@{
    ViewData["Title"] = "View";
}
@using fa18team16BevoBookStore.Controllers
<!--This is the quick search box code-->
<form asp-action="Index" asp-controller="Home" method="get">
    <p class="form-group">
        Search: <input name="SearchString" class="form-control" /><br />
        <button type="submit" class="btn btn-secondary">Search</button>
        <a asp-action="Index" class="btn btn-danger">Show All</a>
    </p>
</form>
<p>Displaying @ViewBag.SelectedBooks out of @ViewBag.TotalBooks </p>
<h2>View</h2>
<div class="form-group">
    <label class="radio">@Html.RadioButton("DateValueSign", 
Classification.NewestFirst)Newest First</label>
    <label class="radio">@Html.RadioButton("DateValueSign", 
Classification.OldestFirst)Oldest First</label>
    <label class="radio">@Html.RadioButton("DateValueSign", 
Classification.MostPopular)Most Popular</label>
    <label class="radio">@Html.RadioButton("DateValueSign", 
Classification.LeastPopular)Least Popular</label>
</div>
<table class="table">
    <thead>
        <tr>
            <th>
                @Html.DisplayNameFor(model => model.UniqueID)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Title)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Author)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Description)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.BookQuantity)
            </th>
            <th></th>
        </tr>
    </thead>
    <tbody>
        @foreach (var item in Model)
        {
            <tr>
                <td>
                    @Html.DisplayFor(modelItem => item.UniqueID)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.Title)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.Author)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.Description)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.BookQuantity)
                </td>
                <td>
                    <a asp-action="Details" asp-route- 
id="@item.BookID">Details</a>
                </td>
            </tr>
        }
    </tbody>
</table>

Answer 1

首先，枚举始终具有相同值的最常见原因是未正确分配值，因此将其分配为其默认值。枚举的默认值为0，这是您在Classification枚举中定义的第一个值。在您的情况下，NewestFirst似乎是默认值。此行为表示未传递DateValueSign值。

第二，对于调试可能与Razor渲染有关的问题，请始终检查检查元素以验证生成的代码。第三，在处理诸如case语句之类的服务器端问题时，debugger非常方便。

关于您的问题，MVC需要枚举的 number 值，否则默认为0。如果您在检查元素中选中单选按钮，则会注意到value属性应该显示value="LeastPopular"之类的字符串时显示value="3"之类的字符串。发生这种情况是因为RadioButton函数将任何枚举指定为字符串。为此，只需将剃刀中的每个枚举都转换为int。

例如，此：

 <label class="radio">@Html.RadioButton("DateValueSign", Classification.NewestFirst)Newest First</label>

成为这个：

<label class="radio">@Html.RadioButton("DateValueSign", (int) Classification.NewestFirst)Newest First</label>

Answer 2

对于您的问题，这是由于您将<label class="radio">@Html.RadioButton("DateValueSign", Classification.NewestFirst)Newest First</label>放置在<form asp-action="Index" asp-controller="Home" method="get">之外，然后无论您为DateValueSign选择什么，它都不会传递给控制器和使用Classification的默认值。

将@Html.RadioButton移至form

<form asp-action="Index" asp-controller="Model" method="get">
    <p class="form-group">
        Search: <input name="SearchString" class="form-control" /><br />
        <div class="form-group">
            <label class="radio">
                @Html.RadioButton("DateValueSign", Classification.NewestFirst)Newest First
            </label>
            <label class="radio">
                @Html.RadioButton("DateValueSign", Classification.OldestFirst)Oldest First
            </label>
            <label class="radio">
                @Html.RadioButton("DateValueSign", Classification.MostPopular)Most Popular
            </label>
            <label class="radio">
                @Html.RadioButton("DateValueSign", Classification.LeastPopular)Least Popular
            </label>
        </div>

        <button type="submit" class="btn btn-secondary">Search</button>
        <a asp-action="Index" class="btn btn-danger">Show All</a>
    </p>
</form>

MVC应用程序，Orderby在家庭控制器索引中不起作用

2 个答案: