Asp.net mvc 5 我应该在MVC 5中也在POST中绑定html.dropdownlistfor吗？

这是我的收获

这是我的帖子

这是我的模型

我的观点有一个类似的下拉列表

当我回来的时候，一切都很好。 当我发布时，数据被保存，但在UI中，我得到一个错误

具有键“Subject”的ViewData项的类型为 “System.String”，但必须是“IEnumerable”类型

---

选项不会在表单中发回。您必须再次创建它们：

[HttpPost]
[Authorize]
public ActionResult SendMessage(MessageModel model)
{
    try {
      if (ModelState.IsValid)
      {
          XmlDocument requestXml = XmlUtil.CreateRequestDocument("message", new
          {
              Message = model.MessageBody,
              Type = model.Subject,
              PatientID = model.PatientId,
              RecipientID = model.RecipientId,
              IsUrgent = model.IsUrgent ? "1" : "0"
          });
        //save message logic here
      }
    }
    catch (Exception ex)
    {
        ModelState.AddModelError("ServerMessage", ex.Message);
    }
    var subjects = this.GetDistributionLists();
    if (subjects != null) {
        ViewBag.Subjects = new SelectList(subjects, "Value", "Text");
    }
    if (Request.IsAjaxRequest())
    {
        return PartialView("SendMessagePartial", model);
    }
    else
    {
        return View(model);
    }
}

---

看看这里，我的朋友@Misters，我没有将数据绑定到DropDownList for的问题。我的问题是当我提交/发布表单时。

[HttpPost]
[Authorize]
public ActionResult SendMessage(MessageModel model)
{
    try {
      if (ModelState.IsValid)
      {
          XmlDocument requestXml = XmlUtil.CreateRequestDocument("message", new
          {
              Message = model.MessageBody,
              Type = model.Subject,
              PatientID = model.PatientId,
              RecipientID = model.RecipientId,
              IsUrgent = model.IsUrgent ? "1" : "0"
          });
        //save message logic here
      }
    }
    catch (Exception ex)
    {
        ModelState.AddModelError("ServerMessage", ex.Message);
    }
    if (Request.IsAjaxRequest())
    {
        return PartialView("SendMessagePartial", model);
    }
    else
    {
        return View(model);
    }
}

public class MessageModel
{
    [DisplayName("RecipientId")]
    public int RecipientId { get; set; }

    [DisplayName("Sender")]
    [StringLength(255)]
    public string Sender { get; set; }

    [DisplayName("SenderId")]
    public int SenderId { get; set; }

    [DisplayName("Message")]
    [StringLength(4000)]
    [Required]
    public string MessageBody { get; set; }

    [DisplayName("Subject")]
    [StringLength(255)]
    [Required]
    public string Subject { get; set; }

    [DisplayName("Patient")]
    [Required]
    public int PatientId { get; set; }

    public bool IsUrgent { get; set; }
}

@Html.DropDownListFor(m => m.Subject, (SelectList)ViewBag.Subjects, new { @class = "form-control" })

[HttpPost]
[Authorize]
public ActionResult SendMessage(MessageModel model)
{
    try {
      if (ModelState.IsValid)
      {
          XmlDocument requestXml = XmlUtil.CreateRequestDocument("message", new
          {
              Message = model.MessageBody,
              Type = model.Subject,
              PatientID = model.PatientId,
              RecipientID = model.RecipientId,
              IsUrgent = model.IsUrgent ? "1" : "0"
          });
        //save message logic here
      }
    }
    catch (Exception ex)
    {
        ModelState.AddModelError("ServerMessage", ex.Message);
    }
    var subjects = this.GetDistributionLists();
    if (subjects != null) {
        ViewBag.Subjects = new SelectList(subjects, "Value", "Text");
    }
    if (Request.IsAjaxRequest())
    {
        return PartialView("SendMessagePartial", model);
    }
    else
    {
        return View(model);
    }
}