在ASP.NET Core中的SelectList中显示数据

问题描述

我尝试了几种不同的方法.我不确定为什么，但是我的SelectList/DropDown为空.它没有显示数据.我不确定我要去哪里错了.

I've tried a few different approaches. I'm not sure why but my SelectList/DropDown is empty. It shows no data. I'm not sure where I am going wrong.

我有一个ASP.NET Core应用程序.实体框架核心. Db首先.我正在使用存储库模式.

I have an ASP.NET Core App. Entity Framework Core. Db First. I am using a repository pattern.

这是我的模特班

public partial class Commodity
{
    public Guid Oid { get; set; }
    public string Code { get; set; }
}

这是我的界面

interface ICommodityRepository
{
    IEnumerable<Commodity> GetAll();
}

我的存储库:

public class CommodityRepository : ICommodityRepository
{
    private ltgwarehouseContext context;

    public CommodityRepository()
    { }

    public IEnumerable<Commodity> GetAll()
    {
        return context.Commodity.ToList();
    }
}

我的控制器:

public class CommoditiesController : Controller
{
    static readonly CommodityRepository commodities = new CommodityRepository();

    public CommoditiesController(CommodityRepository commodities)
    { }

    // GET: /<controller>/
    public IEnumerable<Commodity> CommoditiesList()
    {
        return commodities.GetAll();
    }
}

这是我的视图/HTML标记:

This is my View/HTML Markup:

@model Lansing.BasisMap.Domain.Models.Commodity

<li><select asp-for="@Model.Code" asp-controller="Commodities" asp-action="CommoditiesList"></select> </li>

推荐答案

(我不太熟悉ASP.NET Core中的Tag Helper语法，但是请给我一个机会，如果我愿意的话，请任何人纠正我是错的)

(I'm not too familiar with the Tag Helper syntax in ASP.NET Core, but I'll give it a shot, anyone please correct me if I'm wrong)

• asp-for=""属性不需要@前缀，因为它不是Razor代码，该属性值已经由ASP.NET的解析器处理-仅当您使用的C#语法与HTML(例如，双引号).
• asp-controller和asp-action属性不适用于<select>
• 您没有为<select>提供任何选项，请使用asp-items属性并提供IEnumerable<SelectListItem>或SelectList实例.可以通过您的ViewModel或(我的喜好)通过ViewData(或ViewBag)传递.

• The asp-for="" attribute does not need the @ prefix because it is not Razor code, the attribute value is already handled by ASP.NET's parser - you only need it if you're using C# syntax that is ambiguous with HTML (e.g. double-quotes).
• The asp-controller and asp-action attributes do not apply to <select>
• You are not providing any options to your <select>, use the asp-items attribute and provide IEnumerable<SelectListItem> or a SelectList instance. This can be passed in through your ViewModel or (my preference) through ViewData (or ViewBag).

假设它是ViewData，然后:

public ActionResult YourControllerAction() {

    // stuff
    this.ViewData["items"] = commodities
        .GetAll()
        .Select( c => new SelectListItem() { Text = c.Code, Value = c.Oid.ToString() } )
        .ToList();

    // stuff
    return this.View( viewModel );
}

并在这样的视图中使用它:

And use it in view like this:

<select asp-for="Model.Code" asp-items="@ViewData["items"]" />

此质量检查帖子中还有很多示例:选择标签助手在ASP.NET Core MVC中

There's a lot more examples in this QA posting: Select Tag Helper in ASP.NET Core MVC

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