在 C# 中创建错误

我是一名学生，对C#编程还是新手。目前，我正在与MVC一起做一个项目，它有一个时间表页面。我需要创建一个时间表，但这就是错误出现的地方。我有一个日期选择器功能，如果我在创建之日起 4 天内选择任何内容，我可以创建，但如果选择其他时间，我无法创建。

错误：值不能为空。参数：源

我的计划创建页面

@model Sec.Models.Schedule
@using Sec.Models
@{
ViewBag.Title = "Create";
Layout = "~/Views/Shared/_LayoutPage.cshtml";
Employee currentEmp = null;
if (ViewBag.emp != null)
{
    currentEmp = (Employee)ViewBag.emp;
}
//Employee List
List<Employee> dbsEmployee = ViewBag.Employee;
List<SelectListItem> lstEmployee =
    (from b in dbsEmployee
     orderby b.Id
     select new SelectListItem()
     { Text = b.Name, Value = b.Id.ToString() }).ToList<SelectListItem>();
lstEmployee.Insert(0, new SelectListItem() { Text = "-- Select --", Value = "" });
//Site List
List<Site> dbsSite = ViewBag.Site;
List<SelectListItem> lstsite =
    (from b in dbsSite
     orderby b.Id
     select new SelectListItem()
     { Text = b.Id.ToString() + " -- " + b.Pod + b.Level + b.Gender, Value = b.Id.ToString() }).ToList<SelectListItem>();
lstsite.Insert(0, new SelectListItem() { Text = "-- Select --", Value = "" });
}
@if ((currentEmp != null) && (currentEmp.isAdmin == true))
{
<script>
    $('#datetimepicker1').data("DateTimePicker").FUNCTION()
</script>
<h2>Create</h2>
using (Html.BeginForm())
{
    @Html.AntiForgeryToken()
    <div class="form-horizontal">
        <h4>Schedule</h4>
        <hr />
        @Html.ValidationSummary(true, "", new { @class = "text-danger" })
        <div class="form-group">
            @Html.LabelFor(model => model.Id, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.EditorFor(model => model.Id, new { htmlAttributes = new { @class = "form-control" } })
                @Html.ValidationMessageFor(model => model.Id, "", new { @class = "text-danger" })
            </div>
        </div>
        <div class="form-group">
            @Html.LabelFor(model => model.Employee_Id, "Employee_Id", htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownList("Employee_Id", lstEmployee, htmlAttributes: new { @id = "DrpEmployeeId", @class = "form-control" })
                @Html.ValidationMessageFor(model => model.Employee_Id, "", new { @class = "text-danger" })
            </div>
        </div>
        <div class="form-group">
            @Html.LabelFor(model => model.Site_Id, "Site_Id", htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="col-md-10">
                @Html.DropDownList("Site_Id", lstsite, htmlAttributes: new { @id = "DrpSiteId", @class = "form-control" })
                @Html.ValidationMessageFor(model => model.Site_Id, "", new { @class = "text-danger" })
            </div>
        </div>
        <div class="form-group">
            @Html.LabelFor(model => model.Date, htmlAttributes: new { @class = "control-label col-md-2" })
            <div class="row">
                <div class='col-sm-6'>
                    <div class='input-group date' id='datetimepicker1'>
                        @Html.TextBoxFor(model => model.Date, new { @class = "form-control datepicker", placeholder = "Press the button to enter date and time" })
                        @Html.ValidationMessageFor(model => model.Date)
                        <span class="input-group-addon">
                            <span class="glyphicon glyphicon-calendar"></span>
                        </span>
                    </div>
                </div>
                <script type="text/javascript">
                    $(function () {
                        $('#datetimepicker1').datetimepicker();
                    });
                </script>
            </div>
        </div>
        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="Create" class="btn btn-default" />
            </div>
        </div>
    </div>
}
<div>
    @Html.ActionLink("Back to List", "Index")
</div>
}

我的后端

using (secDBEntities3 dbc = new secDBEntities3())
                {
                    DbSet<Employee> dbe = dbc.Employees;
                    ViewBag.Employee = dbe.ToList();
                    DbSet<Site> dbs = dbc.Sites;
                    ViewBag.Site = dbs.ToList();
                }
                return View();

HTTP帖子

 public ActionResult Create([Bind(Include = "Id,Site_Id,Employee_Id,Date")] Schedule schedule)
    {
        if (ModelState.IsValid)
        {
            var s = db.Schedules.Create();
            s.Id = schedule.Id;
            s.Site_Id = schedule.Site_Id;
            s.Employee_Id = schedule.Employee_Id;
            s.Date = schedule.Date;
            db.Schedules.Add(schedule);
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        return View(schedule);
    }

堆栈跟踪

[ArgumentNullException: Value cannot be null.
Parameter name: source]
   System.Linq.OrderedEnumerable`2..ctor(IEnumerable`1 source, Func`2 keySelector, IComparer`1 comparer, Boolean descending) +4367342
   System.Linq.Enumerable.OrderBy(IEnumerable`1 source, Func`2 keySelector) +62
   ASP._Page_Views_Schedules_Create_cshtml.Execute() in D:'Jncr'Jncrwa'Jncrwa'Views'Schedules'Create.cshtml:13
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +198
   System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +105
   System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +78
   System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +235
   System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +107
   System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +291
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +56
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilterRecursive(IList`1 filters, Int32 filterIndex, ResultExecutingContext preContext, ControllerContext controllerContext, ActionResult actionResult) +420
   System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) +52
   System.Web.Mvc.Async.<>c__DisplayClass2b.<BeginInvokeAction>b__1c() +173
   System.Web.Mvc.Async.<>c__DisplayClass21.<BeginInvokeAction>b__1e(IAsyncResult asyncResult) +100
   System.Web.Mvc.Async.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult) +10
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +27
   System.Web.Mvc.Controller.<BeginExecuteCore>b__1d(IAsyncResult asyncResult, ExecuteCoreState innerState) +13
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +29
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +36
   System.Web.Mvc.Controller.<BeginExecute>b__15(IAsyncResult asyncResult, Controller controller) +12
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +22
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +26
   System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10
   System.Web.Mvc.MvcHandler.<BeginProcessRequest>b__5(IAsyncResult asyncResult, ProcessRequestState innerState) +21
   System.Web.Mvc.Async.WrappedAsyncVoid`1.CallEndDelegate(IAsyncResult asyncResult) +29
   System.Web.Mvc.Async.WrappedAsyncResultBase`1.End() +49
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +28
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9744261
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

我搜索了此错误，但找不到问题的解决方案。