Asp.net mvc 4 System.ArgumentNullException:值不能为null。参数名称：items

我收到错误

System.ArgumentNullException:值不能为null。参数名称：此行的项

：

@Html.DropDownList("empnames", new SelectList(ViewBag.empnames), "Select");

var empnames = (from ename in dc.GetTable<Employee_Detail>() where ename.Region ==rgn select ename.Emp_Name).ToList();
ViewBag.empnames = empnames;

我想从所选的

Emp\u名称中获取相应的
Emp\u id
，并想更新我的表
Enq\u提交

我的模型、控制器和视图如下：

型号：

namespace MvcConQuery.Models
{

[Table("Enq_Submission")]
public class EnquiryModel
{
private ConQueryDataClassesDataContext dc = new ConQueryDataClassesDataContext();
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public Int32 Enq_id { get; set; }
[Required]
[Display(Name="Name")]
public string CustomerName { get; set; }
[ReadOnly(true)]
public string Date
{
get
{
DateTime Date = DateTime.Now;
return Date.ToString("yyyy-MM-dd"); ;
}

set{}

}


[Required]
[Display(Name = "Region")]
public string Region { get; set; }
[Required]
[RegularExpression(@"^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$", ErrorMessage = "Entered phone number format is not valid.")]
[Display(Name = "Phone number")]
public string Ph_No { get; set; }
[Required]
[DataType(DataType.EmailAddress)]
[Display(Name = "Email_id")]
public string Email_id { get; set; }
[Required]
[Display(Name = "Address")]
public string Address { get; set; }
[Required]
[Display(Name = "Query")]
public string Query { get; set; }
public string Referral { get; set; }
public string Feedback { get; set; }
public string Status { get; set; }
public Int32? Emp_id { get; set; }
public string FollowUpDate { get; set; }
public List<EmployeeModel> Employees { get; set; }

}}

namespace MvcConQuery.Models
{
[Table("Employee_Details")]
public class EmployeeModel
{

[Key,Column(Order=0)]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
//[ForeignKey("EnquiryModel")]
public Int32 Emp_id { get; set; }
public string Emp_Name{ get; set; }
//[Key,Column(Order=1)]
public string Region { get; set; }
//[ForeignKey("Region")]
public string Emp_PhNo { get; set; }
public string Emp_Address { get; set; }
public List<EnquiryModel> Enquires { get; set; }


}

}

public ActionResult Edit(int id)
{

EnquiryModel enquirymodel = db.Enquires.Find(id);
if (enquirymodel == null)
{
return HttpNotFound();
}
var rgn=enquirymodel.Region;
var empnames = (from ename in dc.GetTable<Employee_Detail>() where ename.Region ==rgn select ename.Emp_Name).ToList();
ViewBag.empnames = empnames;

return View(enquirymodel);

}

[HttpPost]
public ActionResult Edit(EnquiryModel enquirymodel,string empnames)
{
if (ModelState.IsValid)
{

var empid = (from eid in dc.GetTable<Employee_Detail>() where eid.Emp_Name == empnames select eid.Emp_id).First();
enquirymodel.Emp_id = empid;
db.SaveChanges();
}
return View(enquirymodel);
}

@model MvcConQuery.Models.EnquiryModel

@{
ViewBag.Title = "Edit";

}
<style>
.myClass label{
font-weight:bold;
}
</style>

<h2>Allocate Employee</h2>

@using (Html.BeginForm())
{
@Html.ValidationSummary(true)

<fieldset>
<legend>EnquiryModel</legend>
@Html.HiddenFor(model => model.Enq_id)
@Html.HiddenFor(model => model.CustomerName)
@Html.HiddenFor(model => model.Date)
@Html.HiddenFor(model => model.Region)
@Html.HiddenFor(model => model.Ph_No)
@Html.HiddenFor(model => model.Email_id)
@Html.HiddenFor(model => model.Address)
@Html.HiddenFor(model => model.Query)
@Html.HiddenFor(model => model.Referral)
@Html.HiddenFor(model => model.Feedback)
@Html.HiddenFor(model => model.Status)
@Html.HiddenFor(model => model.FollowUpDate)
@Html.HiddenFor(Model => Model.Emp_id);


<div class="editor-label">
@Html.LabelFor(model => model.CustomerName, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.CustomerName)

<div class="editor-label">
@Html.LabelFor(model => model.Region, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Region)

<div class="editor-label">
@Html.LabelFor(model => model.Ph_No, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Ph_No)

<div class="editor-label">
@Html.LabelFor(model => model.Email_id, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Email_id)

<div class="editor-label">
@Html.LabelFor(model => model.Address, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Address)<div class="editor-label">

@Html.LabelFor(model => model.Query, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Query)


@Html.Label("Select Employee", new { @class = "label" })
@Html.DropDownList("empnames", new SelectList(ViewBag.empnames), "Select");

<p>
<input type="submit" value="Allocate" name="Submit"/>
</p>

</fieldset>
}

<div>
@Html.ActionLink("Back to List", "Index")
</div>

@section Scripts {
@Scripts.Render("~/bundles/jqueryval")
}

namespace mvcquery.Models
{
[表（“Enq_提交”）]
公共类查询模型
{
private AcquiredDataClasseSDataContext dc=新的AcquiredDataClasseSDataContext（）；
[关键]
[DatabaseGeneratedAttribute（DatabaseGeneratedOption.Identity）]
public Int32 Enq_id{get；set；}
[必需]
[显示（Name=“Name”）]
公共字符串CustomerName{get；set；}
[只读（正确）]
公共字符串日期
{
得到
{
DateTime Date=DateTime.Now；
返回日期。ToString（“yyyy-MM-dd”）；
}
集合{}
}
[必需]
[显示（Name=“Region”）]
公共字符串区域{get；set；}
[必需]
[RegularExpression（@“^\（（[0-9]{3}）\）？[-.]（[0-9]{3}）[-.]？（[0-9]{4}）$”，ErrorMessage=“输入的电话号码格式无效。”）]
[显示（Name=“电话号码”）]
公共字符串Ph_No{get；set；}
[必需]
[数据类型（数据类型.电子邮件地址）]
[显示（Name=“Email\u id”）]
公共字符串Email_id{get；set；}
[必需]
[显示（Name=“Address”）]
公共字符串地址{get；set；}
[必需]
[显示（Name=“查询”）]
公共字符串查询{get；set；}
公共字符串引用{get；set；}
公共字符串反馈{get；set；}
公共字符串状态{get；set；}
public Int32？Emp_id{get；set；}
公共字符串FollowUpDate{get；set；}
公共列表雇员{get；set；}
}}
名称空间mvcquery.Models
{
[表（“员工详细信息”）]
公共类雇员模型
{
[键，列（顺序=0）]
[DatabaseGeneratedAttribute（DatabaseGeneratedOption.Identity）]
//[外键（“查询模型”）]
public Int32 Emp_id{get；set；}
公共字符串Emp_Name{get；set；}
//[键，列（顺序=1）]
公共字符串区域{get；set；}
//[外键（“区域”）]
公共字符串Emp_PhNo{get；set；}
公共字符串Emp_地址{get；set；}
公共列表查询{get；set；}
}
}

控制器：

namespace MvcConQuery.Models
{

[Table("Enq_Submission")]
public class EnquiryModel
{
private ConQueryDataClassesDataContext dc = new ConQueryDataClassesDataContext();
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public Int32 Enq_id { get; set; }
[Required]
[Display(Name="Name")]
public string CustomerName { get; set; }
[ReadOnly(true)]
public string Date
{
get
{
DateTime Date = DateTime.Now;
return Date.ToString("yyyy-MM-dd"); ;
}

set{}

}


[Required]
[Display(Name = "Region")]
public string Region { get; set; }
[Required]
[RegularExpression(@"^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$", ErrorMessage = "Entered phone number format is not valid.")]
[Display(Name = "Phone number")]
public string Ph_No { get; set; }
[Required]
[DataType(DataType.EmailAddress)]
[Display(Name = "Email_id")]
public string Email_id { get; set; }
[Required]
[Display(Name = "Address")]
public string Address { get; set; }
[Required]
[Display(Name = "Query")]
public string Query { get; set; }
public string Referral { get; set; }
public string Feedback { get; set; }
public string Status { get; set; }
public Int32? Emp_id { get; set; }
public string FollowUpDate { get; set; }
public List<EmployeeModel> Employees { get; set; }

}}

namespace MvcConQuery.Models
{
[Table("Employee_Details")]
public class EmployeeModel
{

[Key,Column(Order=0)]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
//[ForeignKey("EnquiryModel")]
public Int32 Emp_id { get; set; }
public string Emp_Name{ get; set; }
//[Key,Column(Order=1)]
public string Region { get; set; }
//[ForeignKey("Region")]
public string Emp_PhNo { get; set; }
public string Emp_Address { get; set; }
public List<EnquiryModel> Enquires { get; set; }


}

}

public ActionResult Edit(int id)
{

EnquiryModel enquirymodel = db.Enquires.Find(id);
if (enquirymodel == null)
{
return HttpNotFound();
}
var rgn=enquirymodel.Region;
var empnames = (from ename in dc.GetTable<Employee_Detail>() where ename.Region ==rgn select ename.Emp_Name).ToList();
ViewBag.empnames = empnames;

return View(enquirymodel);

}

[HttpPost]
public ActionResult Edit(EnquiryModel enquirymodel,string empnames)
{
if (ModelState.IsValid)
{

var empid = (from eid in dc.GetTable<Employee_Detail>() where eid.Emp_Name == empnames select eid.Emp_id).First();
enquirymodel.Emp_id = empid;
db.SaveChanges();
}
return View(enquirymodel);
}

@model MvcConQuery.Models.EnquiryModel

@{
ViewBag.Title = "Edit";

}
<style>
.myClass label{
font-weight:bold;
}
</style>

<h2>Allocate Employee</h2>

@using (Html.BeginForm())
{
@Html.ValidationSummary(true)

<fieldset>
<legend>EnquiryModel</legend>
@Html.HiddenFor(model => model.Enq_id)
@Html.HiddenFor(model => model.CustomerName)
@Html.HiddenFor(model => model.Date)
@Html.HiddenFor(model => model.Region)
@Html.HiddenFor(model => model.Ph_No)
@Html.HiddenFor(model => model.Email_id)
@Html.HiddenFor(model => model.Address)
@Html.HiddenFor(model => model.Query)
@Html.HiddenFor(model => model.Referral)
@Html.HiddenFor(model => model.Feedback)
@Html.HiddenFor(model => model.Status)
@Html.HiddenFor(model => model.FollowUpDate)
@Html.HiddenFor(Model => Model.Emp_id);


<div class="editor-label">
@Html.LabelFor(model => model.CustomerName, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.CustomerName)

<div class="editor-label">
@Html.LabelFor(model => model.Region, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Region)

<div class="editor-label">
@Html.LabelFor(model => model.Ph_No, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Ph_No)

<div class="editor-label">
@Html.LabelFor(model => model.Email_id, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Email_id)

<div class="editor-label">
@Html.LabelFor(model => model.Address, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Address)<div class="editor-label">

@Html.LabelFor(model => model.Query, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Query)


@Html.Label("Select Employee", new { @class = "label" })
@Html.DropDownList("empnames", new SelectList(ViewBag.empnames), "Select");

<p>
<input type="submit" value="Allocate" name="Submit"/>
</p>

</fieldset>
}

<div>
@Html.ActionLink("Back to List", "Index")
</div>

@section Scripts {
@Scripts.Render("~/bundles/jqueryval")
}

public ActionResult编辑（int-id）
{
inquiryModel inquiryModel=db.inquires.Find（id）；
if（inquiryModel==null）
{
返回HttpNotFound（）；
}
var rgn=查询模型区域；
var empnames=（来自dc.GetTable（）中的ename，其中ename.Region==rgn选择ename.Emp_Name.ToList（）；
ViewBag.empnames=empnames；
返回视图（查询模型）；
}
[HttpPost]
公共操作结果编辑（查询模型查询模型、字符串名称）
{
if（ModelState.IsValid）
{
var empid=（来自dc.GetTable（）中的eid，其中eid.Emp_Name==empnames选择eid.Emp_id）.First（）；
inquiryModel.Emp_id=empid；
db.SaveChanges（）；
}
返回视图（查询模型）；
}

查看：

namespace MvcConQuery.Models
{

[Table("Enq_Submission")]
public class EnquiryModel
{
private ConQueryDataClassesDataContext dc = new ConQueryDataClassesDataContext();
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public Int32 Enq_id { get; set; }
[Required]
[Display(Name="Name")]
public string CustomerName { get; set; }
[ReadOnly(true)]
public string Date
{
get
{
DateTime Date = DateTime.Now;
return Date.ToString("yyyy-MM-dd"); ;
}

set{}

}


[Required]
[Display(Name = "Region")]
public string Region { get; set; }
[Required]
[RegularExpression(@"^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$", ErrorMessage = "Entered phone number format is not valid.")]
[Display(Name = "Phone number")]
public string Ph_No { get; set; }
[Required]
[DataType(DataType.EmailAddress)]
[Display(Name = "Email_id")]
public string Email_id { get; set; }
[Required]
[Display(Name = "Address")]
public string Address { get; set; }
[Required]
[Display(Name = "Query")]
public string Query { get; set; }
public string Referral { get; set; }
public string Feedback { get; set; }
public string Status { get; set; }
public Int32? Emp_id { get; set; }
public string FollowUpDate { get; set; }
public List<EmployeeModel> Employees { get; set; }

}}

namespace MvcConQuery.Models
{
[Table("Employee_Details")]
public class EmployeeModel
{

[Key,Column(Order=0)]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
//[ForeignKey("EnquiryModel")]
public Int32 Emp_id { get; set; }
public string Emp_Name{ get; set; }
//[Key,Column(Order=1)]
public string Region { get; set; }
//[ForeignKey("Region")]
public string Emp_PhNo { get; set; }
public string Emp_Address { get; set; }
public List<EnquiryModel> Enquires { get; set; }


}

}

public ActionResult Edit(int id)
{

EnquiryModel enquirymodel = db.Enquires.Find(id);
if (enquirymodel == null)
{
return HttpNotFound();
}
var rgn=enquirymodel.Region;
var empnames = (from ename in dc.GetTable<Employee_Detail>() where ename.Region ==rgn select ename.Emp_Name).ToList();
ViewBag.empnames = empnames;

return View(enquirymodel);

}

[HttpPost]
public ActionResult Edit(EnquiryModel enquirymodel,string empnames)
{
if (ModelState.IsValid)
{

var empid = (from eid in dc.GetTable<Employee_Detail>() where eid.Emp_Name == empnames select eid.Emp_id).First();
enquirymodel.Emp_id = empid;
db.SaveChanges();
}
return View(enquirymodel);
}

@model MvcConQuery.Models.EnquiryModel

@{
ViewBag.Title = "Edit";

}
<style>
.myClass label{
font-weight:bold;
}
</style>

<h2>Allocate Employee</h2>

@using (Html.BeginForm())
{
@Html.ValidationSummary(true)

<fieldset>
<legend>EnquiryModel</legend>
@Html.HiddenFor(model => model.Enq_id)
@Html.HiddenFor(model => model.CustomerName)
@Html.HiddenFor(model => model.Date)
@Html.HiddenFor(model => model.Region)
@Html.HiddenFor(model => model.Ph_No)
@Html.HiddenFor(model => model.Email_id)
@Html.HiddenFor(model => model.Address)
@Html.HiddenFor(model => model.Query)
@Html.HiddenFor(model => model.Referral)
@Html.HiddenFor(model => model.Feedback)
@Html.HiddenFor(model => model.Status)
@Html.HiddenFor(model => model.FollowUpDate)
@Html.HiddenFor(Model => Model.Emp_id);


<div class="editor-label">
@Html.LabelFor(model => model.CustomerName, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.CustomerName)

<div class="editor-label">
@Html.LabelFor(model => model.Region, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Region)

<div class="editor-label">
@Html.LabelFor(model => model.Ph_No, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Ph_No)

<div class="editor-label">
@Html.LabelFor(model => model.Email_id, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Email_id)

<div class="editor-label">
@Html.LabelFor(model => model.Address, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Address)<div class="editor-label">

@Html.LabelFor(model => model.Query, new { @class = "label" })
</div>

@Html.DisplayFor(model => model.Query)


@Html.Label("Select Employee", new { @class = "label" })
@Html.DropDownList("empnames", new SelectList(ViewBag.empnames), "Select");

<p>
<input type="submit" value="Allocate" name="Submit"/>
</p>

</fieldset>
}

<div>
@Html.ActionLink("Back to List", "Index")
</div>

@section Scripts {
@Scripts.Render("~/bundles/jqueryval")
}

@model mvcquery.Models.inquirymodel
@{
ViewBag.Title=“编辑”；
}
.myClass标签{
字体大小：粗体；
}
分配员工
@使用（Html.BeginForm（））
{
@Html.ValidationSummary（true）
查询模型
@Html.HiddenFor（model=>model.Enq_id）
@Html.HiddenFor（model=>model.CustomerName）
@Html.HiddenFor（model=>model.Date）
@Html.HiddenFor（model=>model.Region）
@Html.HiddenFor（model=>model.Ph\u No）
@Html.HiddenFor（model=>model.Email\u id）
@Html.HiddenFor（model=>model.Address）
@Html.HiddenFor（model=>model.Query）
@Html.HiddenFor（model=>model.reference）
@Html.HiddenFor（model=>model.Feedback）
@Html.HiddenFor（model=>model.Status）
@Html.HiddenFor（model=>model.FollowUpDate）
@Html.HiddenFor（Model=>Model.Emp_id）；
@LabelFor（model=>model.CustomerName，新的{@class=“label”}）
@DisplayFor（model=>model.CustomerName）
@LabelFor（model=>model.Region，新的{@class=“label”}）
@DisplayFor（model=>model.Region）
@LabelFor（model=>model.Ph_No，new{@class=“label”}）
@DisplayFor（model=>model.Ph\u No）
@LabelFor（model=>model.Email_id，新的{@class=“label”}）
@DisplayFor（model=>model.Email\u id）
@LabelFor（model=>model.Address，新的{@class=“label”}）
@DisplayFor（model=>model.Address）
@LabelFor（model=>model.Query，新的{@class=“label”}）
@DisplayFor（model=>model.Query）
@Label（“选择雇员”，新建{@class=“Label”}）
@DropDownList（“empnames”，新选择列表（ViewBag.empnames），“Select”）；


}
@ActionLink（“返回列表”、“索引”）
@节脚本{
@Scripts.Render（“~/bundles/jqueryval”）
}

有谁能帮我解决这个问题吗？
我想你是在
编辑视图中

与第一个
Edit
操作相反，第二个操作没有这一行：

@Html.DropDownList("empnames", new SelectList(ViewBag.empnames), "Select");

var empnames = (from ename in dc.GetTable<Employee_Detail>() where ename.Region ==rgn select ename.Emp_Name).ToList();
ViewBag.empnames = empnames;

问题是“编辑”希望填充empnames ViewBag值。
不更新表格的原因是控制器中缺少一行代码，即：

db.Entry（inquirymodel）.State=EntityState.Modified

[HttpPost]

    public ActionResult Edit(EnquiryModel enquirymodel,string empnames)
    {
        if (ModelState.IsValid)
        {
            var rgn = enquirymodel.Region;
            var empnamess = (from ename in dc.GetTable<Employee_Detail>() where ename.Region == rgn select ename.Emp_Name).ToList();
            ViewBag.empnames = empnamess;

      var empid = (from eid in dc.GetTable<Employee_Detail>() where eid.Emp_Name == empnames select eid.Emp_id).First();

            db.Entry(enquirymodel).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        return View(enquirymodel);
    }

public ActionResult编辑（查询模型查询模型，字符串名称）
{
if（ModelState.IsValid）
{
var rgn=查询模型区域；
var empnames=（来自dc.GetTable（）中的ename，其中ename.Region==rgn选择ename.Emp_Name.ToList（）；
ViewBag.empnames=empnames；
var empid=（来自dc.GetTable（）中的eid，其中eid.Emp_Name==empnames选择eid.Emp_id）.First（）；
db.Entry（inquiryModel）.State=EntityState.Modified；
db.SaveChanges（）；
返回操作（“索引”）；
}
返回视图（查询模型）；
}
您的问题中有太多的代码，请将其缩小到问题行。什么操作（第一次/第二次）会导致问题？很抱歉，我们不能使用它，因为在第二次编辑的范围内，“empnames”具有不同的含义。@user3350713:但您仍然呈现相同的视图。你必须提供。我有两张桌子，员工桌和工作桌。我有一个下拉列表，其中填充了员工的姓名f