无法在mvc实体框架

Question

首先使用Entity Framework Database（Sql Server 2008）处理ASP.NET MVC 4中的项目。我到处寻找，但我找不到任何解决方案。我面临的情况是：

1. 无法创建新的或更新现有的“实习生”错误消息为： DbUpdateException未由用户代码处理 我尝试使用try / catch异常，但没有帮助。

2. 问题似乎来自我所拥有的下拉列表菜单。在编辑模式下（当它具有值时）不仅不显示显示框，而且不保存数据。它没有做任何事情。 所有自由文本字段都可以。

这是控制器：

    using System.Data.Entity;
using System.Linq;
using System.Web.Mvc;
using InternApp.Models;
using System;
using System.Data.Entity.Infrastructure;


namespace InternApp.Controllers
{
    public class InternController : Controller
    {
        private InternshipProgramEntities db = new InternshipProgramEntities();

        //
        // GET: /Intern/

        public ActionResult Index()
        {
            var interns = db.Interns.Include(i => i.Department).Include(i => i.Intern_Coach).Include(i => i.Location).Include(i => i.Intern_Manager).Include(i => i.School).Include(i => i.Semester).Include(i => i.InternStatu);
            return View(interns.ToList());
        }

        //
        // GET: /Intern/Details/5

        public ActionResult Details(int id = 0)
        {
            Intern intern = db.Interns.Find(id);
            if (intern == null)
            {
                return HttpNotFound();
            }
            return View(intern);
        }

        //
        // GET: /Intern/Create

        public ActionResult Create()
        {        

            ViewBag.DepartmentID = new SelectList(db.Departments, "DepartmentID", "DepartmentName");
            ViewBag.CoachID = new SelectList(db.Intern_Coach.OrderBy(c => c.LastName), "InternCoachID", "CoachFullName");
            ViewBag.LocationID = new SelectList(db.Locations, "LocationID", "BldgName");
            ViewBag.ManagerID = new SelectList(db.Intern_Manager.OrderBy(m => m.LastName), "InternManagerID", "ManagerFullName");
            ViewBag.SchoolID = new SelectList(db.Schools, "SchoolID", "SchoolName");
            ViewBag.SemesterID = new SelectList(db.Semesters, "SemesterID", "SemesterName");
            ViewBag.InternStatusID = new SelectList(db.InternStatus, "InternStatusID", "Status");

            return View();
        }              

        //
        // POST: /Intern/Create

        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create(
            [Bind(Include = "InternID, InFirstName, InLastName, PersonalEmail, PersonalPhone, CHSEmail, CHSPhone, InternStatusID, LastStatusChangeDate, SchoolID, SemesterID, Major, PartTimeInterest, FTEAvailDate, GraduationDate, DepartmentID, TeamName, ManagerID, LocationID, ComputerNumber, ITInterests, InternStartDate, InternEndDate, PTStartDate, PTEndDate, FTEStartDate, FTEEndDate, InternSalary, PTSalary, FTESalary, ProgramFeedback, CoachID")]   
            Intern intern)
        {
            if (ModelState.IsValid)
            {
                try
                {                   
                    db.Interns.Add(intern);
                    db.SaveChanges();
                    return RedirectToAction("Index");
                }
                catch (Exception ex)
                {

                }               
            }
            ViewBag.DepartmentID = new SelectList(db.Departments, "DepartmentID", "DepartmentName", intern.DepartmentID);
            ViewBag.CoachID = new SelectList(db.Intern_Coach, "InternCoachID", "CoachFullName", intern.CoachID);
            ViewBag.LocationID = new SelectList(db.Locations, "LocationID", "BldgName", intern.LocationID);
            ViewBag.ManagerID = new SelectList(db.Intern_Manager, "InternManagerID", "ManagerFullName", intern.ManagerID);
            ViewBag.SchoolID = new SelectList(db.Schools, "SchoolID", "SchoolName", intern.SchoolID);
            ViewBag.SemesterID = new SelectList(db.Semesters, "SemesterID", "SemesterName", intern.SemesterID);
            ViewBag.InternStatusID = new SelectList(db.InternStatus, "InternStatusID", "Status", intern.InternStatusID);

            return View(intern);
        }

        //
        // GET: /Intern/Edit/5

        public ActionResult Edit(int id = 0)
        {
            Intern intern = db.Interns.Find(id);
            if (intern == null)
            {
                return HttpNotFound();
            }
            ViewBag.DepartmentID = new SelectList(db.Departments, "DepartmentID", "DepartmentName", intern.DepartmentID);
            ViewBag.CoachID = new SelectList(db.Intern_Coach, "InternCoachID", "UserName", intern.CoachID);
            ViewBag.LocationID = new SelectList(db.Locations, "LocationID", "BldgName", intern.LocationID);
            ViewBag.ManagerID = new SelectList(db.Intern_Manager, "InternManagerID", "UserName", intern.ManagerID);
            ViewBag.SchoolID = new SelectList(db.Schools, "SchoolID", "SchoolName", intern.SchoolID);
            ViewBag.SemesterID = new SelectList(db.Semesters, "SemesterID", "SemesterName", intern.SemesterID);
            ViewBag.InternStatusID = new SelectList(db.InternStatus, "InternStatusID", "Status", intern.InternStatusID);

            return View(intern);
        }

        //
        // POST: /Intern/Edit/5

        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Edit(
            [Bind(Include = "InternID, InFirstName, InLastName, PersonalEmail, PersonalPhone, CHSEmail, CHSPhone, InternStatusID, LastStatusChangeDate, SchoolID, SemesterID, Major, PartTimeInterest, FTEAvailDate, GraduationDate, DepartmentID, TeamName, ManagerID, LocationID, ComputerNumber, ITInterests, InternStartDate, InternEndDate, PTStartDate, PTEndDate, FTEStartDate, FTEEndDate, InternSalary, PTSalary, FTESalary, ProgramFeedback, CoachID")]
            Intern intern)
        {      
            try
            {
                if (ModelState.IsValid)
                {
                    db.Entry(intern).State = EntityState.Modified;
                    db.SaveChanges();
                    return RedirectToAction("Index");
                }
            }
            catch (DbUpdateException editEx)
            {

            }

            ViewBag.DepartmentID = new SelectList(db.Departments, "DepartmentID", "DepartmentName", intern.DepartmentID);
            ViewBag.CoachID = new SelectList(db.Intern_Coach, "InternCoachID", "UserName", intern.CoachID);
            ViewBag.LocationID = new SelectList(db.Locations, "LocationID", "BldgName", intern.LocationID);
            ViewBag.ManagerID = new SelectList(db.Intern_Manager, "InternManagerID", "UserName", intern.ManagerID);
            ViewBag.SchoolID = new SelectList(db.Schools, "SchoolID", "SchoolName", intern.SchoolID);
            ViewBag.SemesterID = new SelectList(db.Semesters, "SemesterID", "SemesterName", intern.SemesterID);
            ViewBag.InternStatusID = new SelectList(db.InternStatus, "InternStatusID", "Status", intern.InternStatusID);

            return View(intern);
        }

以下是创建视图：

@model InternApp.Models.Intern

@{
    ViewBag.Title = "Create";
    Layout = "~/Views/Shared/_Layout.cshtml";
        var u = new InternApp.Classes.Utilities();
}

<h2 style="margin-left:inherit">Create</h2>

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

<fieldset>  

    <legend>New Intern</legend>
        <div class="form-inline">

                <div class="form-group" >
            @*        @Html.HiddenFor(model => model.InternID)*@
                    @Html.Label("First Name")
                    @Html.EditorFor(model => model.InFirstName)
                    @Html.ValidationMessageFor(model => model.InFirstName)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.InLastName)       
                    @Html.EditorFor(model => model.InLastName)
                    @Html.ValidationMessageFor(model => model.InLastName)
                </div>


    <div class="form-inline">
                <div class="form-group">
                    @Html.LabelFor(model => model.PersonalEmail)        
                    @Html.EditorFor(model => model.PersonalEmail)
                    @Html.ValidationMessageFor(model => model.PersonalEmail)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.PersonalPhone)        
                    @Html.EditorFor(model => model.PersonalPhone)
                    @Html.ValidationMessageFor(model => model.PersonalPhone)
                </div>
            </div>    
    <div class="form-inline">
                <div class="form-group">
                    @Html.LabelFor(model => model.CHSEmail)        
                    @Html.EditorFor(model => model.CHSEmail)
                    @Html.ValidationMessageFor(model => model.CHSEmail)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.CHSPhone)        
                    @Html.EditorFor(model => model.CHSPhone)
                    @Html.ValidationMessageFor(model => model.CHSPhone)
                </div>
         </div>
        </div>
    <div class="form-inline">
                <div class="form-group">
                    @Html.Hidden("InternStatusID")
                    @Html.Label("Status: ")             
               @*     @Html.DropDownList("InternStatusID", String.Empty)       *@
                    @Html.DropDownListFor(model => model.InternStatu.Status, new SelectList(u.StatusDropdown(), "Value", "Text"))
                    @Html.ValidationMessageFor(model => model.InternStatu.Status)
                </div>

                <div class="form-group">
                    @Html.Label("Last Status Change Date")       
                    @Html.TextBoxFor(model => model.LastStatusChangeDate)
                    @Html.ValidationMessageFor(model => model.LastStatusChangeDate)
                </div>
      </div>
    <div class="form-inline">
                <div class="form-group">
                    @Html.Hidden("SchoolID")
                    @Html.Label("School")                   
                    @Html.DropDownListFor(model => model.School.SchoolName, new SelectList(u.SchoolDropdown(), "Value", "Text"))
                    @Html.ValidationMessageFor(model => model.School.SchoolName)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.SemesterID, "Semester")       
                    @Html.DropDownList("SemesterID", String.Empty)
                    @Html.ValidationMessageFor(model => model.SemesterID)
                </div>
 </div>
    <div class="form-inline">
                <div class="form-group">
                    @Html.LabelFor(model => model.Major)       
                    @Html.EditorFor(model => model.Major)
                    @Html.ValidationMessageFor(model => model.Major)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.PartTimeInterest)       
                    @Html.EditorFor(model => model.PartTimeInterest)
                    @Html.ValidationMessageFor(model => model.PartTimeInterest)
                </div>
         </div>
    <div class="form-inline">
                <div class="form-group">
                    @Html.LabelFor(model => model.FTEAvailDate)       
                    @Html.TextBoxFor(model => model.FTEAvailDate)
                    @Html.ValidationMessageFor(model => model.FTEAvailDate)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.GraduationDate)        
                    @Html.TextBoxFor(model => model.GraduationDate)
                    @Html.ValidationMessageFor(model => model.GraduationDate)
                </div>
 </div>
    <div class="form-inline">
                <div class="form-group">
                    @Html.HiddenFor(model => model.DepartmentID)
                    @Html.Label("Department")      
                    @Html.DropDownList("DepartmentID", String.Empty)

                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.TeamName)       
                    @Html.EditorFor(model => model.TeamName)
                    @Html.ValidationMessageFor(model => model.TeamName)
                </div>
     </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.ManagerID, "Intern_Manager")      
                    @Html.DropDownList("ManagerID", String.Empty)
                    @Html.ValidationMessageFor(model => model.ManagerID)
                </div>        

                <div class="form-group">
                    @Html.LabelFor(model => model.LocationID, "Location")      
                    @Html.DropDownList("LocationID", String.Empty)
                    @Html.ValidationMessageFor(model => model.LocationID)
                </div>

    <div class="form-inline">
                <div class="form-group">
                    @Html.LabelFor(model => model.ComputerNumber)       
                    @Html.EditorFor(model => model.ComputerNumber)
                    @Html.ValidationMessageFor(model => model.ComputerNumber)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.ITInterests)      
                    @Html.EditorFor(model => model.ITInterests)
                    @Html.ValidationMessageFor(model => model.ITInterests)
                </div>
</div>
<div class="form-inline">
                <div class="form-group">
                    @Html.LabelFor(model => model.InternStartDate)        
                    @Html.TextBoxFor(model => model.InternStartDate)
                    @Html.ValidationMessageFor(model => model.InternStartDate)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.InternEndDate)        
                    @Html.TextBoxFor(model => model.InternEndDate)
                    @Html.ValidationMessageFor(model => model.InternEndDate)
                </div>
 </div>
<div class="form-inline">
                <div class="form-group">
                    @Html.LabelFor(model => model.PTStartDate)        
                    @Html.TextBoxFor(model => model.PTStartDate)
                    @Html.ValidationMessageFor(model => model.PTStartDate)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.PTEndDate)       
                    @Html.TextBoxFor(model => model.PTEndDate)
                    @Html.ValidationMessageFor(model => model.PTEndDate)
                </div>
 </div>
    <div class="form-inline">
                <div class="form-group">
                    @Html.LabelFor(model => model.FTEStartDate)       
                    @Html.TextBoxFor(model => model.FTEStartDate)
                    @Html.ValidationMessageFor(model => model.FTEStartDate)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.FTEEndDate)      
                    @Html.TextBoxFor(model => model.FTEEndDate)
                    @Html.ValidationMessageFor(model => model.FTEEndDate)
                </div>
 </div>
<div class="form-inline">
                <div class="form-group">
                    @Html.LabelFor(model => model.InternSalary)       
                    @Html.EditorFor(model => model.InternSalary)
                    @Html.ValidationMessageFor(model => model.InternSalary)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.PTSalary)       
                    @Html.EditorFor(model => model.PTSalary)
                    @Html.ValidationMessageFor(model => model.PTSalary)
                </div>
 </div>
    <div class="form-inline">
                <div class="form-group">
                    @Html.LabelFor(model => model.FTESalary)       
                    @Html.EditorFor(model => model.FTESalary)
                    @Html.ValidationMessageFor(model => model.FTESalary)
                </div>

                <div class="form-group">
                    @Html.LabelFor(model => model.ProgramFeedback)        
                    @Html.EditorFor(model => model.ProgramFeedback)
                    @Html.ValidationMessageFor(model => model.ProgramFeedback)
                </div>
  </div>
    <div class="form-inline">        
                <div class="form-group">
                    @Html.LabelFor(model => model.CoachID, "Intern_Coach")       
                    @Html.DropDownList("CoachID", String.Empty)
                    @Html.ValidationMessageFor(model => model.CoachID)
                </div>


</div>

        <div id="fUpload">
            @Html.Label("Attach a File")
            <input type="file" name="fileUpload" id="fileUpload" />
        </div>
    <br />
        <p>
              <input type="submit" value="Create" />
        </p>             

</fieldset>
}

<div style="margin-left:inherit" >
    @Html.ActionLink("Back to List", "Index")
</div>

模特：

    namespace InternApp.Models
{
    using System;
    using System.Collections.Generic;

    public partial class Intern
    {
        public int InternID { get; set; }
        public string InFirstName { get; set; }
        public string InLastName { get; set; }
        public string InternFullName { get { return InFirstName + " " + InLastName; } }
        public string PersonalEmail { get; set; }
        public string PersonalPhone { get; set; }
        public string CHSEmail { get; set; }
        public string CHSPhone { get; set; }
        public int InternStatusID { get; set; }
        public System.DateTime LastStatusChangeDate { get; set; }
        public int SchoolID { get; set; }
        public Nullable<int> SemesterID { get; set; }
        public string Major { get; set; }
        public Nullable<bool> PartTimeInterest { get; set; }
        public Nullable<System.DateTime> FTEAvailDate { get; set; }
        public Nullable<System.DateTime> GraduationDate { get; set; }
        public Nullable<int> DepartmentID { get; set; }
        public string TeamName { get; set; }
        public Nullable<int> ManagerID { get; set; }
        public Nullable<int> LocationID { get; set; }
        public string ComputerNumber { get; set; }
        public string ITInterests { get; set; }
        public Nullable<System.DateTime> InternStartDate { get; set; }
        public Nullable<System.DateTime> InternEndDate { get; set; }
        public Nullable<System.DateTime> PTStartDate { get; set; }
        public Nullable<System.DateTime> PTEndDate { get; set; }
        public Nullable<System.DateTime> FTEStartDate { get; set; }
        public Nullable<System.DateTime> FTEEndDate { get; set; }
        public Nullable<decimal> InternSalary { get; set; }
        public Nullable<decimal> PTSalary { get; set; }
        public Nullable<decimal> FTESalary { get; set; }
        public string ProgramFeedback { get; set; }
        public Nullable<int> CoachID { get; set; }

        public virtual Department Department { get; set; }
        public virtual Intern_Coach Intern_Coach { get; set; }
        public virtual Location Location { get; set; }
        public virtual Intern_Manager Intern_Manager { get; set; }
        public virtual School School { get; set; }
        public virtual Semester Semester { get; set; }
        public virtual InternStatu InternStatu { get; set; }
        public virtual Intern Intern1 { get; set; }
        public virtual Intern Intern2 { get; set; }
    }
}