我正在使用Master-Detail表单，我已经尝试了很长一段时间，但我无法理解这个问题。当我获取数据进行编辑时，数据显示在视图字段中，但这里有一些下拉列表没有填充它们的值，并且发生错误，指出属性不存在。我希望你能理解。我将与你分享代码。
查看：_AddorEdit

@model SomeProject.Models.OrderViewModel

@using (Html.BeginForm("AddorEdit", "Quotation", FormMethod.Post, new { onsubmit = "return SubmitForm(this)" }))
{
    @Html.HiddenFor(model => model.masterQuotId, new { Id = "hiddenMasterQuotId", Name = "hiddenMasterQuotId" })
    @Html.HiddenFor(model => model.orderItemsJson, new { Id = "orderItemsJson", Name = "orderItemsJson" })
    
    if (Model.masterQuotId == 0)
    {
        <!-- New Form -->
    }
    else
    {
        <div class="form-group row">
            <div class="col-md-3">
                <label class="text-gray-700">Quotation Number</label>
                @Html.EditorFor(model => model.quotationNumber, new { htmlAttributes = new { @class = "form-control", @autocomplete = "off", @placeholder = "Quotation Number" } })
            </div>
            <div class="col-md-3">
                <label>Customer</label> @Html.ValidationMessageFor(model => model.customerName)
                @Html.DropDownListFor(model => model.customerName, new SelectList(ViewBag.CustomerNameList, "customerId", "customerName"), "-- Select Customer --", htmlAttributes: new { @class = "form-control" })
            </div>
            <div class="col-md-3">
                <label>Inco Term</label>
                @Html.DropDownListFor(model => model.incoTerm, new SelectList(ViewBag.IncoTermList, "incoTermId", "incoTerm"), "-- Select Inco Term --", htmlAttributes: new { @class = "form-control" })
            </div>
            <div class="col-md-3">
                <label>Inco Term</label>
                @Html.DropDownListFor(model => model.paymentTerm, new SelectList(ViewBag.PaymentTermList, "paymentTermId", "paymentTerm"), "-- Select Payment Term --", htmlAttributes: new { @class = "form-control" })
            </div>
        </div>
        <div class="form-group row">
            <div class="col-md-3">
                <label class="text-gray-700">Date</label>
                @Html.EditorFor(model => model.date, new { htmlAttributes = new { @class = "form-control cDate", @autocomplete = "off", @placeholder = "Date" } })
            </div>
            <div class="col-md-3">
                <label>Quote Price</label>
                <input id="quotePriceDis" type="text" class="form-control" placeholder="0.00" readonly="readonly" />
            </div>
            <div class="col-md-3">
                <label>Final Price</label>
                <input id="finalPriceDis" type="text" class="form-control" placeholder="0.00" readonly="readonly" />
            </div>
            <div class="col-md-3">
                <label>Last Sale</label>
                <input id="lastSaleDisp" type="text" class="form-control" placeholder="0.00" readonly="readonly" />
            </div>
        </div>
        <hr />
        <div class="form-group row">
            <div class="col-12">
                <!-- OrderItemViewModel Fields -->
                <table class="prodTable" id="quoteTable" border="0">
                    <thead>
                        <tr>
                            <th>Supplier</th>
                            <th>Sub Cat</th>
                            <th>Model</th>
                            <th>Price/Unit/Set</th>
                            <th>Qty</th>
                            <th>Disc %</th>
                            <th>Total</th>
                        </tr>
                    </thead>
                    <tbody>

                        @if (Model != null && Model.orderItems != null)
                        {
                            for (int i = 0; i < Model.orderItems.Count; i++)
                            {
                                if (Model.masterQuotId != 0 && i == Model.orderItems.Count - 1)
                                {
                                    <tr id="mainRow" class="mainRow">
                                        <td>
                                            @Html.DropDownListFor(model => model.orderItems[i].supplierName, new SelectList(ViewBag.SupplierNameList, "supplierId", "supplierName"), "-- Select Supplier --", htmlAttributes: new { @class = "form-control supplier", id = "supplierDropdown" })
                                            <span class="error">Required</span>
                                        </td>
                                        <td>
                                            @Html.DropDownListFor(model => model.orderItems[i].productCat, new SelectList(""), "-- Select Cat --", htmlAttributes: new { @class = "form-control productCat", id = "productCatDropdown" })
                                            <span class="error">Required</span>
                                        </td>
                                        <td>
                                            @Html.DropDownListFor(model => model.orderItems[i].productCatModel, new SelectList(""), "-- Select Model --", htmlAttributes: new { @class = "form-control productModel", id = "productCatModelDropdown" })
                                            <span class="error">Required</span>
                                        </td>
                                        <td>
                                            @Html.EditorFor(model => model.orderItems[i].unitPrice, new { htmlAttributes = new { @class = "form-control qPrice", @autocomplete = "off", @placeholder = "Unit Price", id = "unitPrice" } })
                                            <span class="error">Required</span>
                                        </td>
                                        <td>
                                            @Html.EditorFor(model => model.orderItems[i].quantity, new { htmlAttributes = new { @class = "form-control qty", @autocomplete = "off", @placeholder = "Qty", id = "qty" } })
                                            <span class="error">Required</span>
                                        </td>
                                        <td>
                                            @Html.EditorFor(model => model.orderItems[i].discount, new { htmlAttributes = new { @class = "form-control disc", @autocomplete = "off", @placeholder = "Disc", id = "discount" } })
                                            <span class="error">Required</span>
                                        </td>
                                        <td valign="top">
                                            <input type="button" class="btn-size btn btn-success btn-sm btnAddRow" value="Add" id="btnAddRow" />
                                        </td>
                                    </tr>
                                }
                            }
                        }
                        <tr>
                            <td colspan="7">
                                <center><span id="orderItemError" style="color: #ff0000;"></span></center>
                            </td>
                        </tr>
                    </tbody>
                </table>
            </div>
        </div>
        <div id="orderDetailsContainer">

        </div>
        <table class="tableTable table-bordered table-striped" id="orderDetails" width="100%" cellspacing="0">
            <tbody>

                @if (Model != null && Model.orderItems != null)
                {

                    for (int i = 0; i < Model.orderItems.Count; i++)
                    {
                        <tr class="mainRow">
                            <td>
                                @Html.DropDownListFor(model => model.orderItems[i].supplierName, new SelectList(ViewBag.SupplierNameList, "supplierId", "supplierName"), "-- Select Supplier --", htmlAttributes: new { @class = "form-control supplier", id = "supplierDropdown" })
                            </td>
                            <td>
                                @Html.DropDownListFor(model => model.orderItems[i].productCat, new SelectList(""), "-- Select Cat --", htmlAttributes: new { @class = "form-control productCat", id = "productCatDropdown" })
                            </td>
                            <td>
                                @Html.DropDownListFor(model => model.orderItems[i].productCatModel, new SelectList(""), "-- Select Model --", htmlAttributes: new { @class = "form-control productModel", id = "productCatModelDropdown" })
                            </td>
                            <td>
                                @Html.EditorFor(model => model.orderItems[i].unitPrice, new { htmlAttributes = new { @class = "form-control qPrice", @autocomplete = "off", @placeholder = "Unit Price", id = "unitPrice" } })
                            </td>
                            <td>
                                @Html.EditorFor(model => model.orderItems[i].quantity, new { htmlAttributes = new { @class = "form-control qty", @autocomplete = "off", @placeholder = "Qty", id = "qty" } })
                            </td>
                            <td>
                                @Html.EditorFor(model => model.orderItems[i].discount, new { htmlAttributes = new { @class = "form-control disc", @autocomplete = "off", @placeholder = "Disc", id = "discount" } })
                            </td>
                            <td valign="top">
                                <input type="button" class="btn-size btn btn-danger btn-sm btnDelRow" value="Del" id="btnDelRow" />
                            </td>
                        </tr>

                    }
                }
            </tbody>
        </table>
        <div class="modal-footer">
            <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
            <button type="submit" id="submit" class="btn btn-primary">Save Changes</button>
        </div>
    }

}

字符串
产品型号：

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace SomeProject.Models
{
    public class OrderViewModel
    {
        public OrderViewModel()
        {
            // Initialize orderItems with an empty list in the constructor
            orderItems = new List<OrderItemViewModel>();
            orderItems.Add(new OrderItemViewModel()); 
        }
        public int masterQuotId { get; set; }

        // Master Quotation Fields
        [Required(ErrorMessage = "Quotation Number is required.")]
        public string quotationNumber { get; set; }

        public int customerId { get; set; }

        [Required(ErrorMessage = "Customer Name is required.")]
        public string customerName { get; set; }

        [Required(ErrorMessage = "IncoTerm is required.")]
        public string incoTerm { get; set; }

        [Required(ErrorMessage = "Payment Method is required.")]
        public string paymentTerm { get; set; }

        [Required(ErrorMessage = "Date is required.")]
        [DataType(DataType.Date)]
        public DateTime date { get; set; }

        // Master Quotation Details Fields
        public List<OrderItemViewModel> orderItems { get; set; }
        public List<QuotItems> orderItemsJson { get; set; }
        public int? selectedSupplierId { get; set; }
        public List<SelectListItem> SupplierNameList { get; set; }
    }

    public class OrderItemViewModel
    {
        public int masterQuotId { get; set; } 

        public int supplierId { get; set; }
        public string supplierName { get; set; }
        public int productCatId { get; set; }
        public string productCat { get; set; }

        public int productCatModelId { get; set; }
        public string productCatModel { get; set; }

        public decimal unitPrice { get; set; }

        public int quantity { get; set; }

        public decimal discount { get; set; }
    }
}

型
控制器：

[HttpGet]
public ActionResult AddorEdit(int Id = 0)
{
    OrderViewModel orderViewModel = new OrderViewModel();
    if (orderViewModel.orderItems == null)
    {
        orderViewModel.orderItems = new List<OrderItemViewModel>();
    }
    if (Id == 0)
    {
        ViewBag.CustomerNameList = dropdownMethods.Get_CustomersNameList();
        ViewBag.PaymentTermList = dropdownMethods.Get_PaymentTermList();
        ViewBag.IncoTermList = dropdownMethods.Get_IncoTermsList();
        ViewBag.SupplierNameList = dropdownMethods.Get_SuppliersNameList();

        OrderViewModel newOrderViewModel = new OrderViewModel
        {
            orderItems = new List<OrderItemViewModel>()
        };
        return PartialView("_AddorEdit", orderViewModel);
    }
    else
    {
        // Fetch Master Quotation Details
        OrderViewModel fetchedMasterData = dbLayer.GetQuotationMasterDetailsById(Id);

        // Fetch Quotation Items
        List<OrderItemViewModel> fetchedItemsData = dbLayer.GetQuotationItemsDetailsById(Id);

        if (fetchedMasterData != null && fetchedItemsData != null)
        {
            orderViewModel = fetchedMasterData;
            orderViewModel.orderItems = fetchedItemsData;

            List<SelectListItem> SupplierNameList = PopulateDropdown(fetchedItemsData, x => x.supplierId.ToString(), x => x.supplierName, orderViewModel.selectedSupplierId.GetValueOrDefault());
            ViewBag.SupplierNameList = SupplierNameList;

            return PartialView("_AddorEdit", orderViewModel);
        }
        else
        {
            return HttpNotFound();
        }
    }

}

// Common method to populate dropdown
public List<SelectListItem> PopulateDropdown<T>(IEnumerable<T> items, Func<T, string> valueFunc, Func<T, string> textFunc, int selectedValue)
{
    var selectList = new List<SelectListItem>();

    foreach (var item in items)
    {
        var value = (valueFunc(item) != null) ? valueFunc(item) : "DefaultValue";
        var text = (textFunc(item) != null) ? textFunc(item) : "DefaultText";

        var listItem = new SelectListItem
        {
            Value = value,
            Text = text,
            Selected = (value == selectedValue.ToString())
        };

        selectList.Add(listItem);
    }

    return selectList;
}

型
错误代码：
x1c 0d1x的数据
我需要你的帮助。
我搜索了很多，也看到了类似的帖子，但我的问题没有得到解决，所以我在这里分享了这个问题。