将异步方法绑定到DropDownList ASP.NET MVC 5中

加工到：

[Required(ErrorMessage = "This field is required")]
[Display(Name = "Hardware Type")]
public string HardwareType { get; set; }
public IEnumerable<SelectListItem> ListOfHardwares { get; set; }

public interface IHardwareRepository
{
Task<Entities.Hardware>> GetAllHardwareAsync();
}

<div class="form-group">
            @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownListFor(model => model.HardwareType, Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
            </div>
        </div>

public class HardwareController : Controller
    {
private readonly IUnitOfWork _unitOfWork;

        public HardwareController(IUnitOfWork unitOfWork)
        {
            _unitOfWork = unitOfWork;
        }

public async Task<ActionResult> DisplayAll()
        {
            var displayAll = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();

            return View(displayAll);
        }
}

> public async Task<ActionResult> Add()
>         {
>             var model = new ImageDto();
>             var hardwares = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();
> 
>             model.ListOfHardwares = hardwares.Select(h => new SelectListItem
>             {
>                 Text = h.Name,
>                 Value = h.Description
>             });
> 
>             return View();
}

@model MachineDto

    <div class="form-group">
        @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
        </div>

[必需（ErrorMessage=“此字段是必需的”）]
[显示（名称=“硬件类型”）]
公共字符串硬件类型{get；set；}
公共IEnumerable硬件列表{get；set；}

iHardware假设：

[Required(ErrorMessage = "This field is required")]
[Display(Name = "Hardware Type")]
public string HardwareType { get; set; }
public IEnumerable<SelectListItem> ListOfHardwares { get; set; }

public interface IHardwareRepository
{
Task<Entities.Hardware>> GetAllHardwareAsync();
}

<div class="form-group">
            @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownListFor(model => model.HardwareType, Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
            </div>
        </div>

public class HardwareController : Controller
    {
private readonly IUnitOfWork _unitOfWork;

        public HardwareController(IUnitOfWork unitOfWork)
        {
            _unitOfWork = unitOfWork;
        }

public async Task<ActionResult> DisplayAll()
        {
            var displayAll = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();

            return View(displayAll);
        }
}

> public async Task<ActionResult> Add()
>         {
>             var model = new ImageDto();
>             var hardwares = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();
> 
>             model.ListOfHardwares = hardwares.Select(h => new SelectListItem
>             {
>                 Text = h.Name,
>                 Value = h.Description
>             });
> 
>             return View();
}

@model MachineDto

    <div class="form-group">
        @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
        </div>

公共接口IHardwareRepository
{
任务>GetAllHardwareAsync（）；
}

硬件存储：

public async Task<List<Entities.Hardware>> GetAllHardwareAsync()
        {
            var getAllHardware = await _appContext.Hardwares.ToListAsync();

            return getAllHardware;
        }

public异步任务GetAllHardwareAsync（）
{
var getAllHardware=await_appContext.hardware.toListSync（）；
返回getAllHardware；
}

查看：

[Required(ErrorMessage = "This field is required")]
[Display(Name = "Hardware Type")]
public string HardwareType { get; set; }
public IEnumerable<SelectListItem> ListOfHardwares { get; set; }

public interface IHardwareRepository
{
Task<Entities.Hardware>> GetAllHardwareAsync();
}

<div class="form-group">
            @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownListFor(model => model.HardwareType, Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
            </div>
        </div>

public class HardwareController : Controller
    {
private readonly IUnitOfWork _unitOfWork;

        public HardwareController(IUnitOfWork unitOfWork)
        {
            _unitOfWork = unitOfWork;
        }

public async Task<ActionResult> DisplayAll()
        {
            var displayAll = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();

            return View(displayAll);
        }
}

> public async Task<ActionResult> Add()
>         {
>             var model = new ImageDto();
>             var hardwares = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();
> 
>             model.ListOfHardwares = hardwares.Select(h => new SelectListItem
>             {
>                 Text = h.Name,
>                 Value = h.Description
>             });
> 
>             return View();
}

@model MachineDto

    <div class="form-group">
        @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
        </div>

@LabelFor（model=>model.HardwareType，htmlAttributes:new{@class=“controllabel col-md-2”}）
@Html.DropDownListFor（model=>model.HardwareType，model.listofhardware，“--Select--”，new{@class=“form control”}）
@Html.ValidationMessageFor（model=>model.HardwareType，“，new{@class=“text danger”}）

编辑：

public async Task<List<Entities.Hardware>> GetAllHardwareAsync()
        {
            var getAllHardware = await _appContext.Hardwares.ToListAsync();

            return getAllHardware;
        }

控制器：

[Required(ErrorMessage = "This field is required")]
[Display(Name = "Hardware Type")]
public string HardwareType { get; set; }
public IEnumerable<SelectListItem> ListOfHardwares { get; set; }

public interface IHardwareRepository
{
Task<Entities.Hardware>> GetAllHardwareAsync();
}

<div class="form-group">
            @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownListFor(model => model.HardwareType, Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
            </div>
        </div>

public class HardwareController : Controller
    {
private readonly IUnitOfWork _unitOfWork;

        public HardwareController(IUnitOfWork unitOfWork)
        {
            _unitOfWork = unitOfWork;
        }

public async Task<ActionResult> DisplayAll()
        {
            var displayAll = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();

            return View(displayAll);
        }
}

> public async Task<ActionResult> Add()
>         {
>             var model = new ImageDto();
>             var hardwares = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();
> 
>             model.ListOfHardwares = hardwares.Select(h => new SelectListItem
>             {
>                 Text = h.Name,
>                 Value = h.Description
>             });
> 
>             return View();
}

@model MachineDto

    <div class="form-group">
        @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
        </div>

公共类硬件控制器：控制器
{
私人只读i工作单元(unitof工作单元);；
公共硬件控制器（IUnitOfWork unitOfWork）
{
_unitOfWork=unitOfWork；
}
公共异步任务DisplayAll（）
{
var displayAll=await_unitOfWork.HardwareRepository.GetAllHardwareAsync（）；
返回视图（displayAll）；
}
}

EDIT2: 控制器：

[Required(ErrorMessage = "This field is required")]
[Display(Name = "Hardware Type")]
public string HardwareType { get; set; }
public IEnumerable<SelectListItem> ListOfHardwares { get; set; }

public interface IHardwareRepository
{
Task<Entities.Hardware>> GetAllHardwareAsync();
}

<div class="form-group">
            @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownListFor(model => model.HardwareType, Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
            </div>
        </div>

public class HardwareController : Controller
    {
private readonly IUnitOfWork _unitOfWork;

        public HardwareController(IUnitOfWork unitOfWork)
        {
            _unitOfWork = unitOfWork;
        }

public async Task<ActionResult> DisplayAll()
        {
            var displayAll = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();

            return View(displayAll);
        }
}

> public async Task<ActionResult> Add()
>         {
>             var model = new ImageDto();
>             var hardwares = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();
> 
>             model.ListOfHardwares = hardwares.Select(h => new SelectListItem
>             {
>                 Text = h.Name,
>                 Value = h.Description
>             });
> 
>             return View();
}

@model MachineDto

    <div class="form-group">
        @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
        </div>

公共异步任务添加（） > { >var模型=新的ImageDto（）； >var hardwares=await_unitOfWork.HardwareRepository.GetAllHardwareAsync（）； > >model.ListOfHardwares=硬件。选择（h=>new SelectListItem > { >Text=h.名称， >值=h.说明 > }); > >返回视图（）； } 查看：

[Required(ErrorMessage = "This field is required")]
[Display(Name = "Hardware Type")]
public string HardwareType { get; set; }
public IEnumerable<SelectListItem> ListOfHardwares { get; set; }

public interface IHardwareRepository
{
Task<Entities.Hardware>> GetAllHardwareAsync();
}

<div class="form-group">
            @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownListFor(model => model.HardwareType, Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
            </div>
        </div>

public class HardwareController : Controller
    {
private readonly IUnitOfWork _unitOfWork;

        public HardwareController(IUnitOfWork unitOfWork)
        {
            _unitOfWork = unitOfWork;
        }

public async Task<ActionResult> DisplayAll()
        {
            var displayAll = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();

            return View(displayAll);
        }
}

> public async Task<ActionResult> Add()
>         {
>             var model = new ImageDto();
>             var hardwares = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();
> 
>             model.ListOfHardwares = hardwares.Select(h => new SelectListItem
>             {
>                 Text = h.Name,
>                 Value = h.Description
>             });
> 
>             return View();
}

@model MachineDto

    <div class="form-group">
        @Html.LabelFor(model => model.HardwareType, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.Model.ListOfHardwares, "--Select--", new { @class = "form-control" })
            @Html.ValidationMessageFor(model => model.HardwareType, "", new { @class = "text-danger" })
        </div>

@model MachineDto
@LabelFor（model=>model.HardwareType，htmlAttributes:new{@class=“controllabel col-md-2”}）
@DropDownListFor（model=>model.model.listofhardware，“--Select--”，new{@class=“formcontrol”}）
@Html.ValidationMessageFor（model=>model.HardwareType，“，new{@class=“text danger”}）

问题是，现在我想将GetAllHardwareAsync传递给硬件列表，并通过DropDownList显示它。我真的不想用ViewBag来做。有什么想法吗？

---

提前谢谢

在某个地方，您只需要使用存储库的实例在模型上设置值。在何处执行此操作取决于您在何处拥有（或可以获得）存储库实例以及您希望在模型上设置值的位置

例如，在大多数情况下，存储库将位于控制器上，控制器将构建要发送到视图的模型。可能看起来像这样

private IHardwareRepository _repository;

public SomeController(IHardwareRepository repository)
{
    // I'm *assuming* you get the repository from dependency injection
    _repository = repository;
}

public async Task<ActionResult> SomeAction()
{
    var model = new MachineDto();
    model.ListOfHardwares = await _repository.GetAllHardwaresAsync();
    return View(model);
}

编辑：进一步检查后，您的模型似乎需要一个

IEnumerable

，而不仅仅是实际数据本身。我通常建议在视图中而不是在模型中进行这种投影，但这并不足以完全阻止这种做法。特别是如果这个“模型”只是这个视图的一个视图模型

在这种情况下，您只需要一个简单的投影。一旦有了结果列表，就可以将其投影到所需类型的列表中。大概是这样的：

public async Task<ActionResult> SomeAction()
{
    var repository = new HardwareRepository();
    var model = new MachineDto();
    model.ListOfHardwares = await repository.GetAllHardwaresAsync();
    return View(model);
}

public async Task<ActionResult> DisplayAll()
{
    var model = new MachineDto();
    model.ListOfHardwares = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();

    return View(model);
}

public async Task<ActionResult> DisplayAll()
{
    var model = new MachineDto();
    var hardwares = await _unitOfWork.HardwareRepository.GetAllHardwareAsync();
    model.ListOfHardwares = hardwares.Select(h => new SelectListItem
    {
        Text = h.SomeTextProperty,
        Value = h.SomeIdentifierProperty
    });
    return View(model);
}

public异步任务DisplayAll（）
{
var模型=新机器到（）；
var hardwares=await_unitOfWork.HardwareRepository.GetAllHardwareAsync（）；
model.ListOfHardwares=硬件。选择（h=>new SelectListItem
{
Text=h.SomeTextProperty，
值=h.SomeIdentifierProperty
});
返回视图（模型）；
}

---

您对

SomeTextProperty

和

SomeIdentifierProperty

使用什么取决于

Hardware

上存在哪些属性，以及您希望如何使用这些属性来构建选择列表。

如果我像您一样编写，则使用：

model.listofhardware=\u unitOfWork.HardwareRepository.getAllHardwareSync（）

VS表示无法将类型“System.Threading.Tasks.Task”隐式转换为“System.Collections.Generic.IEnumerable”。存在显式转换（是否缺少转换？@Xardas:您忘记了

wait

关键字。使用

等待

，结果是一个

列表

。没有它，结果就是一个

任务

。正如错误所述，它们是不同的类型。事实上，我忘记了wait，但它仍然不能解决问题。@Xardas：你能进一步描述这个问题吗？它以什么方式失败？机器具有从硬件列表中获取的现场硬件类型。硬件列表直接取自数据库，因为硬件可以单独放入数据库。这意味着我有单独的硬件和机器存储库。问题是，我想将返回值从HardwareRepository（顺便说一句，它包含在UnitOfWork中）传递到机器中的硬件列表。起初，我是这样通过ViewBag完成的：

ViewBag.ListOfRpsw=new SelectList（_rpswRepository.GetAllRpsw（），“Name”，“Description”）

成功了，但自从我添加了async&await和UnitOfWork之后，它就停止了工作。