Question

我目前有一个ASP.NET Core 2.0 Web应用程序（通过默认Web应用程序模板在VS 2017中构建）。我有一个带有内置下拉菜单的RazorPage，我想通过SQL查询来填充它。我已经使用Entity Framework Core来建立数据库模型，如下所示：

    public partial class INVOPEContext : DbContext
    {
        public virtual DbSet<PmeFundData> PmeFundData { get; set; }

            modelBuilder.HasAnnotation"Relational:DefaultSchema", "Server\\User");

            modelBuilder.Entity<PmeFundData>(entity =>
            {
                entity.ToTable("PME_FUND_DATA", "dbo");
                entity.Property(e => e.Firm).HasMaxLength(255);
            });
    }


    public partial class PmeFundData
    {
        public string Firm { get; set; }
    }

我已经更新了RazorPage PageModel（pmepe.cshtml.cs）以包括DBContext和Query：

    public class pmepeModel : PageModel
    {
        private readonly INVOPEContext _db;
        public pmepeModel(INVOPEContext db)
        {
            _db = db;
        }

        public IActionResult dropdowns()
        {
            List<PmeFundData> firmList = new List<PmeFundData>();

            firmList = (from Firm in _db.PmeFundData
                        select Firm).Distinct().ToList();

            firmList.Insert(0, new PmeFundData {Firm = "All Firms" });

            ViewBag.ListofFirms = firmList;

            return View();
        }
    }

最后，带有下拉菜单（pmepe.cshtml）的视图如下：

    @page
    @model pmepeModel
    @{
        ViewData["Title"] = "pmepe";
    }

    <select asp-for="dropdowns"
        id="firm" 
        class="dropdown" 
        asp-items= "@(new SelectList(ViewBag.ListofFirms, "Firm"))">
    </select>

我收到的错误是PageModel的当前上下文中不存在ViewBag或View（视图中没有错误-Intellisense对其进行了选择）。我在网上找到的每个示例都是针对MVC而不是RazorPages。通常为MVC提供的解决方案是将查询嵌入到Controller中，并在web.config文件中调整MVC版本。但是RazorPages模板没有控制器，我找不到web.config文件-因此我无法使其在我的应用程序中正常工作。您能提供的任何帮助将不胜感激。

Answer 1

您的代码中存在多个问题。

PmeFundData应该具有Id属性，否则，在运行update-database命令时会收到错误消息。
```
public partial class PmeFundData
{
public int Id { get; set; }
public string Firm { get; set; }
}
```
ViewBag，您可以从Add ViewBag to PageModel #6754跟踪此问题，可以尝试ViewData或PageModel Property来绑定对象。

这是ViewData的简单代码。

    public class PmepeModelModel : PageModel
{
    private readonly CoreRazor2_1.Data.ApplicationDbContext _context;

    public PmepeModelModel(CoreRazor2_1.Data.ApplicationDbContext context)
    {
        _context = context;
    }

    public IActionResult OnGet()
    {
        return Page();
    }
    [BindProperty]
    public int SelectedFirm { get; set; }
    [ViewData]
    public IList<PmeFundData> ListofFirms { get {
            return Dropdowns();
        }
    }
    public IList<PmeFundData> Dropdowns()
    {
        List<PmeFundData> firmList = new List<PmeFundData>();
        firmList = new List<PmeFundData> {
            new PmeFundData{ Id = 1, Firm = "F1"},
            new PmeFundData{ Id = 2, Firm = "F3"},
            new PmeFundData{ Id = 3, Firm = "F2"}
        };
        //firmList = (from Firm in _context.PmeFundData
        //            select Firm).Distinct().ToList();

        firmList.Insert(0, new PmeFundData { Firm = "All Firms" });
        return firmList;
        //ViewData["ListofFirms"] = firmList;
    }

    public async Task<IActionResult> OnPostAsync()
    {
        var value = SelectedFirm;
        if (!ModelState.IsValid)
        {
            return Page();
        }

        _context.PmeFundData.Add(PmeFundData);
        await _context.SaveChangesAsync();

        return RedirectToPage("./Index");
    }
}

查看

@page
@model CoreRazor2_1.Pages.PmepeModelModel

@{
    ViewData["Title"] = "PmepeModel";
}

<h2>PmepeModel</h2>
<h4>PmeFundData</h4>
<hr />
<div class="row">
    <div class="col-md-4">
        <form method="post">
            <select asp-for="@Model.SelectedFirm"
                    class="dropdown"
                    asp-items="@(new SelectList((IEnumerable<PmeFundData>)@ViewData["ListofFirms"], "Id" ,"Firm"))">

            </select>
            <div class="form-group">
                <input type="submit" value="Create" class="btn btn-default" />
            </div>
        </form>
    </div>
</div>
<div>
    <a asp-page="Index">Back to List</a>
</div>

@section Scripts {
    @{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
}

您还可以向Introduction to Razor Pages in ASP.NET Core学习Razor Page

使用SQL查询下拉菜单-ASP.NET Core 2.0; RazorPages; VS 2017;实体框架核心

1 个答案: