好吧，我最近遇到了一个我似乎无法弄清楚的有趣问题。
我得到的错误信息是：
{"The model item passed into the dictionary is null, but this dictionary requires a non-null model item of type 'System.TimeSpan'."}
当我尝试向数据库提交新条目时会发生这种情况。所以，提交内容的细节。
模型类：
public class EventModel
{
[Key]
public int EventID { get; set; }
[DisplayName("Booking title")]
[Required(ErrorMessage="Please provide a title for the booking")]
public string Title { get; set; }
[DataType(DataType.Date)]
[DisplayName("Start date")]
[DisplayFormat(DataFormatString="{0:dd/MM/yyyy}", ApplyFormatInEditMode = true)]
public DateTime StartDateTime { get; set; }
[DisplayName("End date")]
[DataType(DataType.Date)]
[DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}", ApplyFormatInEditMode = true)]
[IsDateAfter("StartDateTime", true, ErrorMessage="End date must be on or after the start date")]
public DateTime EndDateTime { get; set; }
public long StartTicks { get; set; }
public long EndTicks { get; set; }
[NotMapped]
[DisplayName("Start Time")]
public TimeSpan StartTime
{
get { return TimeSpan.FromTicks(StartTicks); }
set { StartTicks = value.Ticks; }
}
[NotMapped]
[DisplayName("End Time")]
public TimeSpan EndTime
{
get { return TimeSpan.FromTicks(EndTicks); }
set { EndTicks = value.Ticks; }
}
[DefaultValue(2)]
[DisplayName("Booking is")]
public int BookingStatus { get; set; }
[DisplayName("Set recurrence")]
[DefaultValue(false)]
public bool DoesRecur { get; set; }
[DisplayName("Set recurrence type")]
public string Pattern { get; set; }
[DisplayName("Set the day this happens on ")]
public int DayIndex { get; set; }
[DisplayName("Choose the day instance this recurs on")]
public int DayCount { get; set; }
[DisplayName("Day ")]
[NotMapped]
public string Day { get; set; }
[DisplayName("Instance")]
[NotMapped]
public string Instance { get; set; }
// links resource to a user/member
[DisplayName("Booked by")]
[NotMapped]
public string BookerName { get; set; }
public Guid MemberID { get; set; }
// links resource to a resource type
[DisplayName("Resource required:")]
public int ResourceID { get; set; }
}
控制器类中的操作方法：
[HttpGet]
public ActionResult Create(DateTime eventDate)
{
var days = from DayOfWeek d in Enum.GetValues(typeof(DayOfWeek))
select new { ID = (int) d, Name = (DayOfWeek)d };
var instance = from DayInstance i in Enum.GetValues(typeof(DayInstance))
select new { ID = (int) i, Name = (DayInstance)i };
MembershipUser mu = Membership.GetUser(HttpContext.Profile.UserName);
CreateEventViewModel model = new CreateEventViewModel()
{
Event = new EventModel()
{
StartDateTime = eventDate,
EndDateTime = eventDate,
MemberID = (Guid)mu.ProviderUserKey
},
Resources = DBContext.Resources.ToList(),
Patterns = DBContext.Patterns.ToList(),
ResourceTypes = DBContext.ResourceTypes.ToList()
};
ViewData["dayOfWeek"] = new SelectList(days, "ID", "Name", DayOfWeek.Monday);
ViewData["dayInstance"] = new SelectList(instance, "ID", "Name", DayInstance.First);
return View(model);
}
[HttpPost]
public ActionResult Create(CreateEventViewModel em)
{
if (ModelState.IsValid)
{
// get the resource turn aournd time
double turnAround = rc.GetResourceTurnAround(em.Event.ResourceID);
MembershipUser mu = Membership.GetUser(HttpContext.Profile.UserName);
em.Event.MemberID = (Guid) mu.ProviderUserKey;
em.Event.BookingStatus = 2;
// need to get the time added to the date.
DateTime actualStartPoint = new DateTime(em.Event.StartDateTime.Ticks + em.Event.StartTicks);
DateTime actualEndPoint = new DateTime(em.Event.EndDateTime.Ticks + em.Event.EndTicks);
em.Event.StartDateTime = actualStartPoint;
em.Event.EndDateTime = actualEndPoint;
// add turn around time to the end of the event
em.Event.EndDateTime = em.Event.EndDateTime.AddMinutes(turnAround);
// needed becase these are handled slighty differently to the rest of the model
em.Event.DayIndex = int.Parse(Request.Form.GetValues("dayOfWeek").GetValue(0).ToString());
em.Event.DayCount = int.Parse(Request.Form.GetValues("dayInstance").GetValue(0).ToString());
DBContext.Events.Add(em.Event);
DBContext.SaveChanges();
// get the resource owner
MembershipUser resourceOwner = Membership.GetUser(rc.GetResourceOwnerByID(em.Event.ResourceID));
// email the admin team and the user the details of this booking
// get the email address of the user making the booking
StringBuilder message = new StringBuilder();
message.AppendFormat("Thank you for your booking, this is now being reviewed by the team.\nThe details of your booking are included for confirmation.\n");
message.AppendFormat("Booking Title: {0}\nResource: {1}\n Date: {2} {3} (this includes our turn around time added on)\n", em.Event.Title, rc.GetResourceNameByID(em.Event.ResourceID), actualStartPoint, actualEndPoint);
message.AppendFormat("You can log in at any time to review your bookings.\nYou will receive an email when the team have reviewed this request\nMany thanks\n");
EmailHandler eh = new EmailHandler();
eh.SetRecipient(Membership.GetUser().Email);
eh.AddAdminEmail();
eh.AddBcc(resourceOwner.Email);
eh.SetSubject("Booking Requested");
eh.SetBody(message.ToString());
eh.sendMessage();
return RedirectToAction("Index");
}
else
{
return View();
}
}
现在查看项目 - 主视图：
@model AssetManager.Models.CreateEventViewModel
@{
ViewBag.Title = "Create";
Layout = "~/Views/Shared/_Layout.cshtml";
}
@using (Html.BeginForm())
{
@Html.ValidationSummary(true)
<fieldset>
<legend id="bookingLegend">Place Booking</legend>
<div class="controlcontainer">
<div class="editor-label">
@Html.LabelFor(model => model.Event.Title)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.Event.Title)
@Html.ValidationMessageFor(model => model.Event.Title)
</div>
</div>
<div class="controlcontainer">
<div class="editor-label">
@Html.LabelFor(model => model.Event.StartDateTime)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.Event.StartDateTime, new { @class = "date" })
@Html.ValidationMessageFor(model => model.Event.StartDateTime)
</div>
</div>
<div class="controlcontainer">
<div class="editor-label timeSelector">
@Html.LabelFor(model => model.Event.StartTime)
</div>
<div class="editor-field timeSelector">
@Html.EditorFor(model => model.Event.StartTime)
@Html.ValidationMessageFor(model => model.Event.StartTime)
</div>
</div>
<div class="controlcontainer">
<div class="editor-label">
@Html.LabelFor(model => model.Event.EndDateTime)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.Event.EndDateTime, new { @class = "date" })
@Html.ValidationMessageFor(model => model.Event.EndDateTime)
</div>
</div>
<div class="controlcontainer">
<div class="editor-label timeSelector">
@Html.LabelFor(model => model.Event.EndTime)
</div>
<div class="editor-field timeSelector">
@Html.EditorFor(model => model.Event.EndTime)
@Html.ValidationMessageFor(model => model.Event.EndTime)
</div>
</div>
<div class="controlcontainer">
<div class="editor-label">
@Html.Label("Select Resource Type")
</div>
<div class="editor-field">
@Html.DropDownList("ResourceTypes", new SelectList(Model.ResourceTypes, "ResourceTypeID", "Title"), "-- Select Resource Type --", new { @id = "ddlResourceTypes" })
</div>
</div>
<div class="controlcontainer">
<div class="editor-label">
@Html.LabelFor(model => model.Event.ResourceID)
</div>
<div class="editor-field">
@Html.DropDownListFor(model => model.Event.ResourceID, new SelectList(Enumerable.Empty<SelectListItem>(), "ResourceType", "Name"), "-- Select Resource --", new { @id = "ddlResources" })
@Html.ValidationMessageFor(model => model.Event.ResourceID)
</div>
</div>
<div class="controlcontainer">
<div class="editor-label">
@Html.LabelFor(model => model.Event.DoesRecur)
</div>
<div class="editor-field">
@Html.EditorFor(model => model.Event.DoesRecur)
@Html.ValidationMessageFor(model => model.Event.DoesRecur)
</div>
</div>
<div id="recurType" class="controlcontainer">
<div class="editor-label">
@Html.LabelFor(model => model.Event.Pattern)
</div>
<div class="editor-field">
@Html.DropDownListFor(model => model.Event.Pattern, new SelectList(Model.Patterns, "PatternCode", "Pattern"), "-- Select Recurrence Pattern --")
@Html.ValidationMessageFor(model => model.Event.Pattern)
</div>
</div>
<div id="recurDayHappens" class="controlcontainer">
<div class="editor-label">
@Html.LabelFor(model => model.Event.DayIndex)
</div>
<div class="editor-field">
@Html.DropDownList("dayOfWeek")
@Html.ValidationMessageFor(model => model.Event.DayIndex)
</div>
</div>
<div id="recurInstance" class="controlcontainer">
<div class="editor-label">
@Html.LabelFor(model => model.Event.DayCount)
</div>
<div class="editor-field">
@Html.DropDownList("dayInstance")
@Html.ValidationMessageFor(model => model.Event.DayCount)
</div>
</div>
<div class="controlcontainer">
<p>
<input class="subButton" type="submit" value="Create" />
<input id="cancelBtn" class="cancelButton" type="button" value="Cancel" onclick="location.href='@Url.Action("Index", "Calendar")'" />
</p>
</div>
</fieldset>
}
然后有一个TimeSpan项目的编辑器模板：
@model TimeSpan
@Html.DropDownList("Hours", Enumerable.Range(0, 24)
.Select(i => new SelectListItem { Value = i.ToString(),
Text = i.ToString(), Selected = Model.Hours == i })) :
@Html.DropDownList("Minutes", Enumerable.Range(0, 60)
.Select(i => new SelectListItem { Value = i.ToString(),
Text = i.ToString(), Selected = Model.Minutes == i }))
最后一个TimeBinder类：
public class TimeBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
// Ensure there's incomming data
var key_hours = bindingContext.ModelName + ".Hours";
var valueProviderResult_hours = bindingContext.ValueProvider
.GetValue(key_hours);
var key_minutes = bindingContext.ModelName + ".Minutes";
var valueProviderResult_minutes = bindingContext.ValueProvider
.GetValue(key_minutes);
if (valueProviderResult_hours == null || string.IsNullOrEmpty(valueProviderResult_hours.AttemptedValue)
|| valueProviderResult_minutes == null || string.IsNullOrEmpty(valueProviderResult_minutes.AttemptedValue))
{
return null;
}
// Preserve it in case we need to redisplay the form
bindingContext.ModelState.SetModelValue(key_hours, valueProviderResult_hours);
bindingContext.ModelState.SetModelValue(key_minutes, valueProviderResult_minutes);
// Parse
var hours = ((string[])valueProviderResult_hours.RawValue)[0];
var minutes = ((string[])valueProviderResult_minutes.RawValue)[0];
// A TimeSpan represents the time elapsed since midnight
var time = new TimeSpan(Convert.ToInt32(hours), Convert.ToInt32(minutes), 0);
return time;
}
}
就是这样，这就是涉及的所有代码。我完全不知道为什么会出现这种错误。关于原因和解决方案的任何想法或建议都非常感谢。
非常感谢 nathj07
修改 Pk，所以我尝试了一些与TimeSpan编辑器模板不同的东西：
@model TimeSpan?
@Html.DropDownList("Hours", Enumerable.Range(0, 24)
.Select(i => new SelectListItem
{
Value = i.ToString(),
Text = i.ToString(),
Selected = Model.HasValue ? Model.Value.Hours == i : false
})) :
@Html.DropDownList("Minutes", Enumerable.Range(0, 60)
.Select(i => new SelectListItem
{
Value = i.ToString(),
Text = i.ToString(),
Selected = Model.HasValue ? Model.Value.Minutes == i : false
}))
这似乎已经克服了这个错误，但现在我得到了一个问题。在视图中有一个DropDownList（“ResourceTypes”....）这实际上是一个下拉列表，用于控制DropDownListFor（model =＆gt; model.Event.ResourceID .....）中出现的内容。简单的JavaScript：
$(document).ready(function () {
$("#ddlResourceTypes").change(function () {
var idResourceType = $('#ddlResourceTypes').val();
$.getJSON("/Resource/LoadResourcesByType", { id: idResourceType },
function (resourceData) {
var select = $("#ddlResources");
select.empty();
select.append($('<option/>', {
value: 0,
text: "-- Select Resource --"
}));
$.each(resourceData, function (index, itemData) {
select.append($('<option/>', {
value: itemData.Value,
text: itemData.Text
}));
});
});
});
});
现在问题是：
对象引用未设置为对象的实例
在DropDownList（“ResourceTypes”.....）
上关于这个的任何想法？
答案 0 :(得分：1)
当您发布无效表单时，您将使用代码return View()结束。
因此，在不传递模型的情况下显示相同的视图，模型将为null。您的代码第一次真正需要一个值是在TimeSpan的编辑器中。该值现在可以为空，但您从不测试它为空的情况。
将回报更改为：
return View(em);
传递模型，或使用GET操作中的代码重建并传递模型：
return Create(/* Your create date */);
评论后修改
ModelBinder中的错误可能由以下行引起：
var hours = ((string[])valueProviderResult_hours.RawValue)[0];
var minutes = ((string[])valueProviderResult_minutes.RawValue)[0];
您将数组转换为string[]。我会尽可能晚地转换为字符串，并通过以下方式使其更具错误证明：
var hours = Convert.ToString(((object[])valueProviderResult_hours.RawValue).FirstOrDefault()) ?? "00";
这只会转换为一个对象数组，因此失败的变化较小。取第一个元素，或返回null，并使用Convert将其转换为字符串，如果结果仍为null，则返回“00”。
答案 1 :(得分：0)
在部分视图中点击断点并检查Model对象，在某处您会发现部分视图的错误对象。这是导致此错误的原因