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我有一个简单的表 - 使用 SqlCommand 语句有选择地查询，然后使用 SqlDataReader 读入 HTML 表。我希望能够通过使用简单的 HTML 表单（从控制器获取其功能 - 即：UpdateProductPage 和 UpdateProduct）来更新表格内容。我正在使用包装视图模型来将产品与其特定类型相关联。但是，我似乎无法打开包含用于更新内容的 HTML 表单的视图，因为我被以下错误阻止：

“传递到字典中的模型项的类型为‘Homework_5.ViewModels.WrapperViewModel’，但此字典需要‘System.Collections.Generic.List`1[Homework_5.ViewModels.ProductViewModel]’类型的模型项”

我正在努力理解这个错误。

这是我的包装视图模型：

namespace Homework_5.ViewModels
{
    public class WrapperViewModel
    {
        public ProductViewModel product;
        public List<TypeViewModel> typeList = new List<TypeViewModel>();
    }
}

UpdateProductPage 控制器 - 确实有效（使用断点测试） - 永远不会遇到问题：

//Update an existing product in the database
        public ActionResult UpdateProductPage(int id)
        {
            WrapperViewModel updateModel = new WrapperViewModel();
            updateModel.product = Global.productList.Where(p => p.ProductID == id).FirstOrDefault();
            try
            {
                SqlCommand webstoreCommand = new SqlCommand("Select * from ProductType", webstoreConnection);
                webstoreConnection.Open();
                SqlDataReader webstoreReader = webstoreCommand.ExecuteReader();
                while (webstoreReader.Read())
                {
                    TypeViewModel type = new TypeViewModel();
                    type.TypeID = (int)webstoreReader["ID"];
                    type.TypeName = webstoreReader["TypeName"].ToString();
                    updateModel.typeList.Add(type);
                }
            }
            catch (Exception)
            {
                ViewBag.Status = 0;
            }
            finally
            {
                webstoreConnection.Close();
            }
            return View(updateModel);
        }

UpdateProduct 控制器 - 永远不会运行（根据断点 - 在到达此控制器之前抛出异常：

[HttpPost]
        public ActionResult UpdateProduct(int Id, string Description, double Price, int Quantity, string Image, int TypeID)
        {
            try
            {
                SqlCommand webstoreUpdateCommand = new SqlCommand("Update Product Set Description = '" + Description + "', Price = '" + Price + "', Quantity = '" + Quantity + " where ID = " + Id, webstoreConnection);
                webstoreConnection.Open();
            }
            catch (Exception)
            {
                ViewBag.Status = 0;
            }
            finally
            {
                webstoreConnection.Close();
            }
            return RedirectToAction("ViewProductPage");
        }

HTML 表单（带有必要的输入 - 应该预先填写相应的信息：

model Homework_5.ViewModels.WrapperViewModel

@{
    ViewBag.Title = "UpdateProductPage";
}

<h2>Update Selected Product - ID Value: @Model.product.ProductID</h2>

<div class="update-product-contents">
    @using (Html.BeginForm("UpdateProduct", "AdminProduct", FormMethod.Post))
    {
        @Html.Hidden("Id", Model.product.ProductID, new { @class = "form-control" });
        <label>Description:</label>
        @Html.TextBox("Description", Model.product.Description, new { @class = "form-control", @type = "text", required = "required" });
        <label>Price:</label>
        @Html.TextBox("Price", Model.product.Price, new { @class = "form-control", @type = "number", required = "required" });
        <label>Quantity:</label>
        @Html.TextBox("Quantity", Model.product.Quantity, new { @class = "form-control", @type = "number", required = "required" });
        <label>Image:</label>
        @Html.TextBox("Image", Model.product.ImagePath, new { @class = "form-control", @type = "file", required = "required" });
        <label>Product Type:</label>
        @Html.DropDownList("TypeID", new SelectList(Model.typeList, "TypeID", "TypeName", Model.product.Type.TypeID), new { @class = "form-control", required = "required" });
        <button class="btn btn-outline-dark" type="submit">Add to product database</button>
    }
</div>

最后是打开更新页面的按钮：

<a href="@Url.Action("UpdateProductPage", "AdminProduct", new { id = product.ProductID })">
       <i class="fas fa-edit" id="edit-icon"></i>
</a>
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