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我使用代碼優先與EF。驗證似乎失敗的下拉列表與錯誤System.NullReferenceException：對象引用未設置爲對象的實例。當我保存一條記錄時，會發生這種情況，我故意將控件留空以測試驗證。即使下拉列表本身有選擇，也會發生。驗證失敗，下拉MVC
這裏是我的部分觀點：
<div class="editor">
@Html.LabelFor(model => model.EmployeeID)
@Html.DropDownListFor(model => model.EmployeeID, new SelectList(Model.Employees, "Value", "Text"))
@Html.ValidationMessageFor(model => model.EmployeeID)
</div>
如果我用一個文本框驗證工作：
<div class="editor">
@Html.LabelFor(model => model.EmployeeID)
@Html.TextBoxFor(model => model.EmployeeID, new { style = "width: 250px;" })
@Html.ValidationMessageFor(model => model.EmployeeID)
</div>
這裏是我創建控制器操作：
public ActionResult Create()
{
var e = iEmployeeRepository.GetAll();
var visitorLogViewModel = new VisitorLogViewModel
{
Employees = e.Select(x => new SelectListItem
{
Value = x.EmployeeID,
Text = x.EmployeeName
})
};
return View(visitorLogViewModel);
}
//
// POST: /VisitorLogs/Create
[HttpPost]
public ActionResult Create(VisitorLog visitorlog)
{
if (ModelState.IsValid) {
iVisitorlogRepository.Add(visitorlog);
iVisitorlogRepository.Save();
return RedirectToAction("Search");
} else {
return View();
}
}
我的視圖模型：
public class VisitorLogViewModel
{
public int Id { get; set; }
[Display(Name = "Visitor Name")]
public string VisitorName { get; set; }
[Display(Name = "Company Name")]
public string CompanyName { get; set; }
[Required(ErrorMessage = "Employee ID is required.")]
[Display(Name = "GB Employee")]
public string EmployeeID { get; set; }
[Display(Name = "Visit Reason")]
public string VisitReason { get; set; }
[Display(Name = "Time In")]
public DateTime TimeIn { get; set; }
[Display(Name = "Time Out")]
public DateTime TimeOut { get; set; }
[Display(Name = "GB Employee")]
public string EmployeeName { get; set; }
public IEnumerable Employees { get; set; }
public VisitorLog VisitorLog { get; set; }
}
而我的驗證部分型號：
[MetadataType(typeof(VisitorLogMetaData))]
public partial class VisitorLog
{
}
public class VisitorLogMetaData
{
[Required(ErrorMessage = "Visitor name is required.")]
[MaxLength(128)]
public string VisitorName { get; set; }
[Required(ErrorMessage = "Company name is required.")]
[MaxLength(128)]
public string CompanyName { get; set; }
[Required(ErrorMessage = "GB Employee is required.")]
[MaxLength(128)]
public string EmployeeID { get; set; }
[Required(ErrorMessage = "Visit reason is required.")]
[MaxLength(254)]
public string VisitReason { get; set; }
[Required(ErrorMessage = "Time in is required.")]
public DateTime TimeIn { get; set; }
[Required(ErrorMessage = "Time out reason is required.")]
public DateTime TimeOut { get; set; }
}
最後我的模型：
public partial class VisitorLog
{
public int Id { get; set; }
public string VisitorName { get; set; }
public DateTime TimeIn { get; set; }
public DateTime TimeOut { get; set; }
public string CompanyName { get; set; }
public string EmployeeID { get; set; }
public string VisitReason { get; set; }
// Navigation properties
[ForeignKey("EmployeeID")]
public virtual Employee Employee { get; set; }
}
我看了有在MVC剃刀關於DropDownListFor一個錯誤，但我不知道這是否適用於我的情況。我嘗試了一些解決方案，但他們並沒有爲我工作。我正在使用4.5框架。
謝謝。
編輯：
一件事我注意到，當我提交頁面和下拉元素上停止錯誤：
@Html.DropDownListFor(model => model.EmployeeID, new SelectList(Model.Employees, "Value", "Text"))
在Model.Employees的型號爲NULL，就像是失去其綁定頁面時綁定。