Question

我是初学者。我正在处理此ASP.NET Core MVC项目，我正在尝试通过提交ViewModel将POST传递给form方法，以便我可以将数据保存在{{} 1}}。我的Database方法完成后，我会看到以下GET：

RuntimeBinderException：无法将类型'System.Collections.Generic.List'隐式转换为'System.Collections.Generic.IEnumerable'。存在显式转换（您是否错过了演员？

查看：

RuntimeBinderException

控制器：

<div class="row">
    <div class="col-sm-4">
        <div class="input-group fg-float">
            <div class="fg-line form-chose">
                <label asp-for="LocationName" class="fg-labels" for="locationName"></label>
                    <select asp-for="LocationName" asp-items="ViewBag.Locations" class="chosen disabledropdowncntrl" data-placeholder="Choose a Location" name="locationName" id="dropDownLocationNames">
                        <option value=""></option>
                    </select>
            </div>
        </div>
    </div>
</div>

视图模型：

// GET: ~/Inventory/Locate/Id
    public IActionResult Locate(int Id)
    {
        InventoryLocationsHistoryViewModel locationsHistoryVM = new InventoryLocationsHistoryViewModel();

        // Populating Locations DropDownList
        var locationsList = new List<InventoryLocations>();
        locationsList = _context.InventoryLocations.ToList();
        var locations = locationsList.OrderBy(l => l.LocationName).Select(us => new SelectListItem { Value = us.LocationId.ToString(), Text = us.LocationName }).ToList();
        ViewBag.Locations = locationsList;
        ...
        ...
        return View(locationsHistoryVM);
    }

我做错了什么？

Answer 1

您错误地设置了ViewBag.Locations。您还可以折叠大量代码，因为您将整个列表放入内存以排序和选择2列。这将创建一个select语句，该语句仅选择所需的2列，并在sql server端执行排序。

// GET: ~/Inventory/Locate/Id
    public IActionResult Locate(int Id)
    {
        InventoryLocationsHistoryViewModel locationsHistoryVM = new InventoryLocationsHistoryViewModel();


        var locations = new SelectList(_context.InventoryLocations.OrderBy(l => l.LocationName)
            .ToDictionary(us => us.LocationId, us => us.LocationName), "Key", "Value");
        ViewBag.Locations = locations;

        ...
        ...
        return View(locationsHistoryVM);
    }

无法将类型'System.Collections.Generic.List <inventorylocations>'隐式转换为'System.Collections.Generic.IEnumerable <selectlistitem>'

1 个答案: