ViewModel 的模型状态无效 - C# ASP.NET CORE

Question

希望是一个基本问题，我为联系人创建了一个“创建”页面，该页面创建了系统中所有客户的列表。我使用 ViewModel 来执行此操作，这很好。但是现在在客户模型上，我已将 CustomerName 字段指定为必填项，这导致 ModelState.IsValid 为假，我无法弄清楚原因。

客户

public class Customer
    {
        public int CustomerId { get; set; }
        [Required]
        [Display(Name = "Customer Name")]
        public string? CustomerName { get; set; }
        public ICollection<Contact> Contacts { get; set; }
        public ICollection<Job> Jobs { get; set; }
    }

联系方式

public class Contact
    {
        public int ContactId { get; set; }
        [Required]
        [Display(Name = "First Name")]
        public string FirstName { get; set; }
        [Required]
        [Display(Name = "Last Name")]
        public string LastName { get; set; }
        [Display(Name = "Email Address")]
        public string EmailAddress { get; set; }
        public string Telephone { get; set; }
        public Customer Customer { get; set; }
    }

视图模型

    public class ContactDetailViewModel
    {
        public Contact Contact { get; set; }
        public Customer Customer { get; set; }
        public List<SelectListItem> Customers { get; set; }
    }

表格

        <form asp-action="Create">
            <div asp-validation-summary="ModelOnly" class="text-danger"></div>
            <div class="form-group">
                <label asp-for="Contact.FirstName" class="control-label"></label>
                <input asp-for="Contact.FirstName" class="form-control" />
                <span asp-validation-for="Contact.FirstName" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.LastName" class="control-label"></label>
                <input asp-for="Contact.LastName" class="form-control" />
                <span asp-validation-for="Contact.LastName" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.EmailAddress" class="control-label"></label>
                <input asp-for="Contact.EmailAddress" class="form-control" />
                <span asp-validation-for="Contact.EmailAddress" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Contact.Telephone" class="control-label"></label>
                <input asp-for="Contact.Telephone" class="form-control" />
                <span asp-validation-for="Contact.Telephone" class="text-danger"></span>
            </div>
            <div class="form-group">
                <label asp-for="Customer.CustomerName" class="control-label"></label>
                <select class="form-control dropdown" asp-for="Customer.CustomerId" asp-items="@Model.Customers">
                    <option></option>
                </select>
                <span asp-validation-for="Customer.CustomerId" class="text-danger"></span>
            </div>
            <div class="form-group">
                <input type="submit" value="Create" class="btn btn-primary" />
            </div>
        </form>

控制器

public async Task<IActionResult> Create([Bind("ContactId,FirstName,LastName,EmailAddress,Telephone")] Contact contact, ContactDetailViewModel contactDetailViewModel)
        {
            contact.Customer = await _context.Customers.FirstOrDefaultAsync(c => c.CustomerId == contactDetailViewModel.Customer.CustomerId);
            //Has to be a better way of doing this??? Why is it faling without... 06/03/2021
            //ModelState.Remove("Customer.CustomerName");

            if (ModelState.IsValid)
            {
                _context.Add(contact);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            return View(contact);
        }

如果我不包括 ModelState.Remove("Customer.CustomerName");然后它不起作用。但是我不想对 CustomerName 做任何事情，因为我只想将 Contact.Customer 更新为“新”选定的客户。

谢谢！

Answer 1

你的班级有错误。将 CustomerId 添加到联系人：

public class Contact
    {
        public int ContactId { get; set; }
        [Required]
        [Display(Name = "First Name")]
        public string FirstName { get; set; }
        [Required]
        [Display(Name = "Last Name")]
        public string LastName { get; set; }
        [Display(Name = "Email Address")]
        public string EmailAddress { get; set; }
        public string Telephone { get; set; }
        public int  CustomerId { get; set; }
        public virtual  Customer Customer { get; set; }
    }

并修复视图：

<div class="form-group">
                <label asp-for="Customer.CustomerName" class="control-label"></label>
                <select class="form-control dropdown" asp-for="Contact.CustomerId" asp-items="@Model.Customers">
                    <option></option>
                </select>
                <span asp-validation-for="Contact.CustomerId" class="text-danger"></span>
            </div>

您也可以修复操作：

 contact.Customer = await _context.Customers.FirstOrDefaultAsync(c => c.CustomerId == contactDetailViewModel.Contact.CustomerId);

但它是一个冗余代码。您根本不需要此代码，因为您可以在没有此代码的情况下保存联系人。

您还需要通过添加 CustomerId 来修复绑定：

public async Task<IActionResult> Create([Bind("ContactId, CustomerId, FirstName,LastName,EmailAddress,Telephone")] Contact contact, ContactDetailViewModel contactDetailViewModel)

顺便说一下，您将整个客户包含在模型中仅用于

  <label asp-for="Customer.CustomerName" class="control-label"></label>

您可以将 Customer 属性保留为 null 并使用以下代码：

  <label asp-for="Contact.CustomerId" class="control-label"> Customer </label>